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What has the Juno spacecraft taught us about Jupiter?

Untangle the mysteries of our solar system’s planets and moons. Check out Astronomy ’s free downloadable eBook, The Hitchhiker’s Guide to Planets , which contains everything you need to know about our solar systems major players. “Jupiter is central to understanding how planets in our solar system formed,” writes Caltech planetary scientist David Stevenson in the May Annual Review of Earth and Planetary Sciences . “And it has secrets still to be unlocked.”

With a little over a year left in the probe’s primary mission, Juno scientists are busy trying to understand how all the intriguing disparate discoveries mesh into a coherent picture of Jupiter’s inner life . The primary mission is scheduled to last until July 2021, though the team hopes to extend Juno’s visit for a few more years beyond that.

Meanwhile, here are four of Juno’s greatest hits to date.

Polar cyclone party

Juno is justly famous for its surreal photos of Jupiter’s swirling cloudscapes. But while the probe does have an excellent camera, not to mention a fanbase of amateur Jupiter enthusiasts ready to transform its images into science art, what makes these photos truly unique is Juno’s highly elongated, 53-day orbit: a trajectory that maximizes the spacecraft’s science potential while minimizing its exposure to Jupiter’s fierce radiation belts.

Around the planet’s south pole, Juno spied five cyclones, each wider than the United States, parked around a central cyclone of the same size. Not to be outdone, the north pole revealed eight similar cyclones encircling their own polar vortex. Remarkably, the storms didn’t seem to be going anywhere. With each of Juno’s flybys, the storms stayed put.

Complexity under the clouds

Because Jupiter is what astronomers call a gas giant planet, there is no point asking what conditions are like on its surface: It doesn’t have one. Instead, the hydrogen and helium gas that make up the bulk of Jupiter’s atmosphere simply get denser and denser the farther down you go, until the hydrogen becomes a liquid metal.

But there is still plenty of action in Jupiter’s swirling clouds, which are thought to be a mix of water and ammonia. And, as researchers have discovered via a microwave instrument that lets Juno probe beneath the clouds, there is plenty of complexity underneath as well.

And then there is the case of the missing ammonia. “We had assumed … that as soon as you drop below the [clouds], everything ought to be well mixed,” says mission lead Scott Bolton, a planetary scientist at Southwest Research Institute in San Antonio, Texas. Jupiter is, after all, a rapidly spinning ball of fluid (a day lasts just under 10 hours). But Juno’s microwave readings show that this mixing picture holds true only near the equator. It falls apart as you move north or south into Jupiter’s midlatitudes, where there is nowhere near as much ammonia as researchers expected.

To see why, Tristan Guillot, a planetary scientist at Côte d’Azur Observatory in France, and others developed computer models of Jupiter’s atmosphere and found that, away from the equator, ammonia might readily dissolve into water ice particles lofted up from below . This would reduce the amount of ammonia gas in these areas. It also means that the weather in Jupiter’s midlatitudes may feature hail-like storms of ammonia-soaked “mushballs” : frozen nuggets of roughly one part ammonia and two parts water.

A humongous smeared-out center

Although Jupiter doesn’t have a surface, researchers had a running argument before Juno’s arrival as to whether the planet had a core — a solid ball of heavier elements gathered at the planet’s center. They could argue it either way. In one common tale of Jupiter’s birth, rocky debris slowly coalesced into a solid mass up to 10 times as hefty as Earth. The gravity of that mass then hoovered up all the gas in its vicinity, surrounding itself with the deep hydrogen-helium atmosphere we see today. But in a different origin story, a pocket of gas swirling around the infant sun collapsed in on itself, creating a more-or-less pure hydrogen-helium world without a rocky core.

Hybrid magnetism

Jupiter’s huge fuzzy core undoubtedly has implications for other aspects of the planet’s behavior — one of them being the planet’s unusual, contorted magnetic field.

For decades, the textbook picture of the Jovian magnetic field was that it resembled Earth’s — which is to say that it looked like the field of a really big bar magnet, with a well-defined magnetic north pole on one end and a well-defined south pole on the other. Quick peeks from earlier spacecraft seemed to confirm that picture.

But the textbooks were wrong. Juno’s measurements show that the magnetic field in Jupiter’s northern hemisphere looks completely different from its southern counterpart . It’s as if someone took a bar magnet, bent it almost in half, frayed one end, split the other end, and then stuck the whole thing in the planet at a cockeyed angle. In the north is the frayed end: Rather than emerging around one central spot, the magnetic field sprouts like weeds along a long high-latitude band. In the south is the split end: Some of the field plunges back into the planet around the south pole while some is concentrated in a spot just south of the equator.

This magnetic field geometry is not seen anywhere else in the solar system. The southern hemisphere resembles Earth’s field, which scientists call dipolar (because it has two poles). The north has more in common with Uranus and Neptune, where the fields are more complex.

“It was weird to have essentially … one hemisphere Earth and one hemisphere Uranus and Neptune,” says Kimberly Moore, a Caltech astrophysicist and a lead author of several studies of Juno’s magnetic findings.

Planetary magnetic fields are generated by electrically conductive fluids in their interior. The unusual fields at Uranus and Neptune may be due to these fluids being restricted to a thinner region of the planet, relative to their size. Something similar might be happening at Jupiter thanks to its dilute core, says Moore. The north-south dichotomy may also emerge from all this complexity.

“That can really change the geometry of the patterns you can come up with,” she says. But that’s just one idea. Helium rain might also wreak havoc on the magnetic field, as could penetrating winds.

Giant distinctions

If Juno has taught us nothing else, it’s that no two giant planets are alike. At first glance, Jupiter has a lot in common with Saturn, for example. But despite both being big balls of mostly hydrogen and helium, they’ve gone down quite different paths.

Jupiter has conga lines of polar cyclones; Saturn has just one vortex per pole (one of which is six-sided!). Jupiter’s magnetic field is a hodge-podge; Saturn’s is pretty boring. Jupiter’s atmosphere is multicolored and banded; Saturn’s is relatively unblemished.

“Giant planets must come in different flavors,” Bolton says. “We need to understand that if we’re going to understand them in general, because the same physics must dictate everything.”

10.1146/knowable-060420-1

Trained as an astronomer, Christopher Crockett is a freelance science journalist living in Arlington, Virginia. His closest run-in with Jupiter was when he got to peer at it through the gigantic 2.7-meter telescope at McDonald Observatory in Texas. The view must have resembled what Juno saw during its final approach. He can be reached at [email protected] .

This article originally appeared in Knowable Magazine , an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter .

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Jupiter is the fifth planet from our Sun and is, by far, the largest planet in the solar system – more than twice as massive as all the other planets combined. Jupiter's stripes and swirls are actually cold, windy clouds of ammonia and water, floating in an atmosphere of hydrogen and helium. Jupiter’s iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years.

Jupiter is surrounded by dozens of moons. Jupiter also has several rings, but unlike the famous rings of Saturn, Jupiter’s rings are very faint and made of dust, not ice.

Jupiter, being the biggest planet, gets its name from the king of the ancient Roman gods.

Potential for Life

Jupiter’s environment is probably not conducive to life as we know it. The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.

While planet Jupiter is an unlikely place for living things to take hold, the same is not true of some of its many moons. Europa is one of the likeliest places to find life elsewhere in our solar system. There is evidence of a vast ocean just beneath its icy crust, where life could possibly be supported.

Size and Distance

With a radius of 43,440.7 miles (69,911 kilometers), Jupiter is 11 times wider than Earth. If Earth were the size of a nickel, Jupiter would be about as big as a basketball.

From an average distance of 484 million miles (778 million kilometers), Jupiter is 5.2 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes Sunlight 43 minutes to travel from the Sun to Jupiter.

Orbit and Rotation

Jupiter has the shortest day in the solar system. One day on Jupiter takes only about 10 hours (the time it takes for Jupiter to rotate or spin around once), and Jupiter makes a complete orbit around the Sun (a year in Jovian time) in about 12 Earth years (4,333 Earth days).

Its equator is tilted with respect to its orbital path around the Sun by just 3 degrees. This means Jupiter spins nearly upright and does not have seasons as extreme as other planets do.

With four large moons and many smaller moons, Jupiter forms a kind of miniature solar system. Jupiter has 80 moons. Fifty-seven moons have been given official names by the International Astronomical Union (IAU). Another 23 moons are awaiting names.

Jupiter's four largest moons – Io, Europa, Ganymede, and Callisto – were first observed by the astronomer Galileo Galilei in 1610 using an early version of the telescope. These four moons are known today as the Galilean satellites, and they're some of the most fascinating destinations in our solar system. Io is the most volcanically active body in the solar system. Ganymede is the largest moon in the solar system (even bigger than the planet Mercury). Callisto’s very few small craters indicate a small degree of current surface activity. A liquid-water ocean with the ingredients for life may lie beneath the frozen crust of Europa, making it a tempting place to explore.

› More on Jupiter's Moons

Discovered in 1979 by NASA's Voyager 1 spacecraft, Jupiter's rings were a surprise, as they are composed of small, dark particles and are difficult to see except when backlit by the Sun. Data from the Galileo spacecraft indicate that Jupiter's ring system may be formed by dust kicked up as interplanetary meteoroids smash into the giant planet's small innermost moons.

Jupiter took shape when the rest of the solar system formed about 4.5 billion years ago when gravity pulled swirling gas and dust in to become this gas giant. Jupiter took most of the mass left over after the formation of the Sun, ending up with more than twice the combined material of the other bodies in the solar system. In fact, Jupiter has the same ingredients as a star, but it did not grow massive enough to ignite.

About 4 billion years ago, Jupiter settled into its current position in the outer solar system, where it is the fifth planet from the Sun.

The composition of Jupiter is similar to that of the Sun – mostly hydrogen and helium. Deep in the atmosphere, pressure and temperature increase, compressing the hydrogen gas into a liquid. This gives Jupiter the largest ocean in the solar system – an ocean made of hydrogen instead of water. Scientists think that, at depths perhaps halfway to the planet's center, the pressure becomes so great that electrons are squeezed off the hydrogen atoms, making the liquid electrically conducting like metal. Jupiter's fast rotation is thought to drive electrical currents in this region, generating the planet's powerful magnetic field. It is still unclear if deeper down, Jupiter has a central core of solid material or if it may be a thick, super-hot and dense soup. It could be up to 90,032 degrees Fahrenheit (50,000 degrees Celsius) down there, made mostly of iron and silicate minerals (similar to quartz).

As a gas giant, Jupiter doesn’t have a true surface. The planet is mostly swirling gases and liquids. While a spacecraft would have nowhere to land on Jupiter, it wouldn’t be able to fly through unscathed either. The extreme pressures and temperatures deep inside the planet crush, melt, and vaporize spacecraft trying to fly into the planet.

Jupiter's appearance is a tapestry of colorful cloud bands and spots. The gas planet likely has three distinct cloud layers in its "skies" that, taken together, span about 44 miles (71 kilometers). The top cloud is probably made of ammonia ice, while the middle layer is likely made of ammonium hydrosulfide crystals. The innermost layer may be made of water ice and vapor.

The vivid colors you see in thick bands across Jupiter may be plumes of sulfur and phosphorus-containing gases rising from the planet's warmer interior. Jupiter's fast rotation – spinning once every 10 hours – creates strong jet streams, separating its clouds into dark belts and bright zones across long stretches.

With no solid surface to slow them down, Jupiter's spots can persist for many years. Stormy Jupiter is swept by over a dozen prevailing winds, some reaching up to 335 miles per hour (539 kilometers per hour) at the equator. The Great Red Spot, a swirling oval of clouds twice as wide as Earth, has been observed on the giant planet for more than 300 years. More recently, three smaller ovals merged to form the Little Red Spot, about half the size of its larger cousin.

Findings from NASA’s Juno probe released in October 2021 provide a fuller picture of what’s going on below those clouds. Data from Juno shows that Jupiter’s cyclones are warmer on top, with lower atmospheric densities, while they are colder at the bottom, with higher densities. Anticyclones, which rotate in the opposite direction, are colder at the top but warmer at the bottom.

The findings also indicate these storms are far taller than expected, with some extending 60 miles (100 kilometers) below the cloud tops and others, including the Great Red Spot, extending over 200 miles (350 kilometers). This surprising discovery demonstrates that the vortices cover regions beyond those where water condenses and clouds form, below the depth where sunlight warms the atmosphere.

The height and size of the Great Red Spot mean the concentration of atmospheric mass within the storm potentially could be detectable by instruments studying Jupiter’s gravity field. Two close Juno flybys over Jupiter’s most famous spot provided the opportunity to search for the storm’s gravity signature and complement the other results on its depth.

With their gravity data, the Juno team was able to constrain the extent of the Great Red Spot to a depth of about 300 miles (500 kilometers) below the cloud tops.

Belts and Zones In addition to cyclones and anticyclones, Jupiter is known for its distinctive belts and zones – white and reddish bands of clouds that wrap around the planet. Strong east-west winds moving in opposite directions separate the bands. Juno previously discovered that these winds, or jet streams, reach depths of about 2,000 miles (roughly 3,200 kilometers). Researchers are still trying to solve the mystery of how the jet streams form. Data collected by Juno during multiple passes reveal one possible clue: that the atmosphere’s ammonia gas travels up and down in remarkable alignment with the observed jet streams.

Juno’s data also shows that the belts and zones undergo a transition around 40 miles (65 kilometers) beneath Jupiter’s water clouds. At shallow depths, Jupiter’s belts are brighter in microwave light than the neighboring zones. But at deeper levels, below the water clouds, the opposite is true – which reveals a similarity to our oceans.

Polar Cyclones Juno previously discovered polygonal arrangements of giant cyclonic storms at both of Jupiter’s poles – eight arranged in an octagonal pattern in the north and five arranged in a pentagonal pattern in the south. Over time, mission scientists determined these atmospheric phenomena are extremely resilient, remaining in the same location.

Juno data also indicates that, like hurricanes on Earth, these cyclones want to move poleward, but cyclones located at the center of each pole push them back. This balance explains where the cyclones reside and the different numbers at each pole.

Magnetosphere

The Jovian magnetosphere is the region of space influenced by Jupiter's powerful magnetic field. It balloons 600,000 to 2 million miles (1 to 3 million kilometers) toward the Sun (seven to 21 times the diameter of Jupiter itself) and tapers into a tadpole-shaped tail extending more than 600 million miles (1 billion kilometers) behind Jupiter, as far as Saturn's orbit. Jupiter's enormous magnetic field is 16 to 54 times as powerful as that of the Earth. It rotates with the planet and sweeps up particles that have an electric charge. Near the planet, the magnetic field traps swarms of charged particles and accelerates them to very high energies, creating intense radiation that bombards the innermost moons and can damage spacecraft.

Jupiter's magnetic field also causes some of the solar system's most spectacular aurorae at the planet's poles.

• NASA Planetary Photojournal - Jupiter
• Planetary Rings Node
• NASA's Juno Mission

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April 4, 2022

A closer look at Jupiter's origin story

by NCCR PlanetS

One of the most important open questions in planetary formation theory is the story of Jupiter's origin. Using sophisticated computer modeling, researchers of the University of Zurich (UZH) and the National Centre of Competence in Research (NCCR) PlanetS now shed new light on Jupiter's formation history. Their results were published in The Astrophysical Journal Letters .

A curious enrichment of heavy elements

When the Galileo spacecraft released a probe that parachuted into Jupiter's atmosphere in 1995, it showed among other things that heavy elements (elements heavier than helium) are enriched there. At the same time, recent structure models of Jupiter that are based on gravity field measurements by the Juno spacecraft suggest that Jupiter's interior is not uniform but has a complex structure.

"Since we now know that the interior of Jupiter is not fully mixed, we would expect heavy elements to be in a giant gas planet's deep interior as heavy elements are mostly accreted during the early stages of the planetary formation," study co-author, Professor at the University of Zurich and member of the NCCR PlanetS, Ravit Helled begins to explain. "Only in later stages, when the growing planet is sufficiently massive, can it effectively attract large amounts of light element gases like hydrogen and helium. Finding a formation scenario of Jupiter which is consistent with the predicted interior structure as well as with the measured atmospheric enrichment is therefore challenging yet critical for our understanding of giant planets," Helled says. Of the many theories that have so far been proposed, none could provide a satisfying answer.

A long migration

"Our idea was that Jupiter had collected these heavy elements in the late stages of its formation by migrating. In doing so, it would have moved through regions filled with so-called planetesimals—small planetary building blocks that are composed of heavy element materials—and accumulated them in its atmosphere," study lead-author Sho Shibata, who is a postdoctoral researcher at the University of Zurich and a member of the NCCR PlanetS, explains.

Yet, migration by itself is no guarantee for accreting the necessary material. "Because of complex dynamical interactions, the migrating planet does not necessarily accrete the planetesimals in its path. In many cases, the planet actually scatters them instead—not unlike a shepherding dog scattering sheep," Shibata points out. The team therefore had to run countless simulations to determine if any migration pathways resulted in sufficient material accretion.

"What we found was that a sufficient number of planetesimals could be captured if Jupiter formed in the outer regions of the solar system—about four times further away from the Sun than where it is located now—and then migrated to its current position. In this scenario, it moved through a region where the conditions favored material accretion—an accretion sweet spot, as we call it," Sho reports.

A new era in planetary science

Combining the constraints introduced by the Galileo probe and Juno data, the researchers have finally come up with a satisfying explanation. "This shows how complex giant gas planets are and how difficult it is to realistically reproduce their characteristics" Ravit Helled points out.

"It took us a long time in planetary science to get to a stage where we can finally explore these details with updated theoretical models and numerical simulations. This helps us close gaps in our understanding not only of Jupiter and our solar system, but also of the many observed giant planets orbiting far away stars," Helled concludes.

Journal information: Astrophysical Journal Letters

Provided by NCCR PlanetS

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Planet Jupiter, explained

From its mysterious core to its stormy surface, there's plenty to learn about the fifth planet from the sun.

The fifth planet from the sun, Jupiter is what watercolor dreams are made of. Vibrant bands of clouds ripple around its thick atmosphere, making up a world so large that more than 1,300 Earths could fit inside. Its Great Red Spot seems to peer out from the swirling vapors like an enormous eye in the face of a striped giant.

Though seemingly serene when viewed from the relative safety of our home world, Jupiter is a chaotic and stormy place . The gas giant planet's spots and swirls come from massive storms that whip up prevailing winds as fast as 335 miles an hour at the equator—faster than any known winds on Earth.

That includes the Great Red Spot, which is a massive hurricane-like storm called an anticyclone. It's far bigger and longer lasting than any tempests that have ever raged across our planet's surface: It rotates in an ever-present oval that's more than the width of the entire Earth, although it has been shrinking for as long as humans have been observing it.

Gas, liquid, or solid?

Jupiter is a massive ball of gas. Its clouds are composed of ammonia and water vapor drifting in an atmosphere of hydrogen and helium. The particular cloud chemistries are likely the magic behind the planet's vibrant colors, but the exact reasons for Jupiter's painted appearance remains unknown.

Below the gassy upper layers, the pressure and temperature increase so much that atoms of hydrogen eventually compress into a liquid. Pressures climb so high that the hydrogen loses its electrons, and the soupy mess can host an electrical charge, just like metal.

The planet's fast spin on its axis means that one Jupiter day lasts less than 10 Earth hours, and it sparks electrical currents that may drive the planet's intense and massive magnetic field, which is 16 to 54 times as powerful as Earth's.

Multitude of moons

Jupiter is the second brightest planet in the night sky, after Venus , which allowed early astronomers to spot and study the massive planet hundreds of years ago. In January 1610, astronomer Galileo Galilei spotted what he thought were four small stars tagging along with Jupiter. These pinpricks of light are actually Jupiter's four largest moons, now known as the Galilean moons: Io, Europa, Ganymede, and Callisto.

Many of these celestial orbs are as remarkable as Jupiter itself. The largest moon in the solar system, Ganymede is also the only moon known to have its own magnetic field. Volcanoes rage on Io's surface, earning it the title of the solar system's most volcanically active body. And scientists believe Europa sports a deep, vast ocean beneath its icy crust , making it a top candidate in the hunt for alien life.

But these are not the planet's only celestial tag-alongs. Jupiter has dozens more—and there may still be more to find. In 2003 alone, astronomers identified 23 new moons. And in June of 2018, researchers discovered 12 more Jovian moons that wander in oddball paths around the giant world.

Missions to Jupiter

Since Galileo first laid telescope-enhanced eyes on Jupiter, scientists have continued to study the curious world from both the ground and the sky. In 1979, NASA's Voyager 1 and 2 spacecraft zipped by the gas giant, taking tens of thousands of pictures as they passed by. Among the surprises from these missions, the data revealed that giant Jupiter sports thin, dusty rings.

And when NASA's Juno spacecraft began orbiting Jupiter in 2016, it quickly started sending back breathtaking images. The stunning pictures revealed that the planet is even more wild than we once thought. Juno returned some of the first detailed looks at the planet's poles , which revealed cyclone swarms gyrating on its surface with roots that likely extend deep below the upper bands of clouds .

Though Jupiter has been so intensely examined, many mysteries remain. One enduring question is what drives Jupiter's Great Red Spot, and what will happen to it in the future. Then there's the question of what actually lies at Jupiter's core. Magnetic field data from the Juno spacecraft suggest that the planet's core is surprisingly large and seems to be made of a partially dissolved solid material. Whatever that is, it's searing hot. Scientists estimate the temperature in this region could be up to 90,032 degrees Fahrenheit —hot enough to melt titanium.

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Science Overview

The principal goal of NASA’s Juno mission is to understand the origin and evolution of Jupiter. Underneath its dense cloud cover, Jupiter safeguards secrets about the fundamental processes and conditions that governed our solar system during its formation. As our primary example of a giant planet, Jupiter can also provide critical knowledge for understanding the planetary systems being discovered around other stars.

With its suite of science instruments, Juno will investigate the existence of a possible solid planetary core, map Jupiter’s intense magnetic field, measure the amount of water and ammonia in the deep atmosphere, and observe the planet’s auroras.

Juno will let us take a giant step forward in our understanding of how giant planets form and the role these titans played in putting together the rest of the solar system.

Jupiter’s Origins and Interior

Theories about solar system formation all begin with the collapse of a giant cloud of gas and dust, or nebula, most of which formed the infant sun, our star. Like the sun, Jupiter is mostly hydrogen and helium, so it must have formed early, capturing most of the material left after our star came to be. How this happened, however, is unclear. Did a massive planetary core form first and capture all that gas gravitationally, or did an unstable region collapse inside the nebula, triggering the planet’s formation? Differences between these scenarios are profound.

Even more importantly, the composition and role of icy planetesimals, or small protoplanets, in planetary formation hangs in the balance — and with them, the origin of Earth and other terrestrial planets. Icy planetesimals likely were the carriers of materials like water and carbon compounds that are the fundamental building blocks of life.

Unlike Earth, Jupiter’s giant mass allowed it to hold onto its original composition, providing us with a way of tracing our solar system’s history. Juno will measure the amount of water and ammonia in Jupiter’s atmosphere and help determine if the planet has a core of heavy elements, constraining models on the origin of this giant planet and thereby the solar system. By mapping Jupiter’s gravitational and magnetic fields, Juno will reveal the planet’s interior structure and measure the mass of the core.

How deep Jupiter’s colorful zones, belts and other features penetrate is one of the most outstanding fundamental questions about the giant planet. Juno will determine the global structure and motions of the planet’s atmosphere below the cloud tops for the first time, mapping variations in the atmosphere’s composition, temperature, clouds and patterns of movement down to unprecedented depths.

Magnetosphere

Juno will provide the first close look at Jupiter's poles, probing forces in the magnetosphere that connect the giant, fast-rotating planet's exterior with its deep interior. (Background image from Cassini; top inset: Jupiter auroras from the Hubble Space Telescope; bottom inset: Cassini at Saturn) Credit NASA/JPL-Caltech

Deep in Jupiter’s atmosphere, under great pressure, hydrogen gas is squeezed into a fluid known as metallic hydrogen. At these enormous pressures, the hydrogen acts like an electrically conducting metal, which is believed to be the source of the planet’s intense magnetic field. This powerful magnetic environment creates the brightest auroras in our solar system, as charged particles precipitate down into the planet’s atmosphere. Juno will directly sample the charged particles and magnetic fields near Jupiter’s poles for the first time, while simultaneously observing the auroras in ultraviolet light produced by the extraordinary amounts of energy crashing into the polar regions. These investigations will greatly improve our understanding of this remarkable phenomenon, and also of similar magnetic objects, like young stars with their own planetary systems.

Juno Science Objectives

The primary science objectives of the mission are as follows:

Origin Determine the abundance of water and place an upper limit on the mass of Jupiter’s possible solid core to decide which theory of the planet’s origin is correct

Interior Understand Jupiter’s interior structure and how material moves deep within the planet by mapping its gravitational and magnetic fields

Atmosphere Map variations in atmospheric composition, temperature, cloud opacity and dynamics to depths greater than 100 bars at all latitudes.

Magnetosphere Characterize and explore the three-dimensional structure of Jupiter’s polar magnetosphere and auroras

The overall goal of the Juno mission is to improve our understanding of the solar system by understanding the origin and evolution of Jupiter. It addresses science objectives central to three NASA Science divisions: Solar System (Planetary), Earth–Sun System (Heliophysics), and Universe (Astrophysics).

Juno’s primary science goal of understanding the formation, evolution, and structure of Jupiter is directly related to the conditions in the early solar system, which led to the formation of our planetary system. The mass of Jupiter’s possible solid core and the abundance of heavy elements in the atmosphere discriminate among models for giant planet formation. Juno constrains the core mass by mapping the gravitational field, and measures through microwave sounding the global abundances of oxygen (water) and nitrogen (ammonia).

Juno reveals the history of Jupiter by mapping the gravitational and magnetic fields with sufficient resolution to constrain Jupiter’s interior structure, the source region of the magnetic field, and the nature of deep convection. By sounding deep into Jupiter’s atmosphere, Juno determines to what depth the belts and zones penetrate. Juno provides the first survey and exploration of the three-dimensional structure of Jupiter’s polar magnetosphere.

Juno's Science Instruments

Microwave Radiometer (MWR) Juno’s Microwave Radiometer instrument will probe beneath Jupiter’s cloud tops to provide data on the atmosphere's structure, movement and chemical composition to a depth as great as 1,000 atmospheres — about 342 miles (550 kilometers) below the visible cloud tops. In particular, MWR will determine the amount of water in the planet's atmosphere.

Juno will use its Microwave Radiometer (MWR) instrument to probe Jupiter's deep atmosphere, revealing new insights about its structure and composition. The instrument will make measurements that enable scientists to determine the amount of water in the planet's atmosphere. This information is the missing key to understanding Jupiter's formation.

Five of Juno's six MWR antennas are located on one side of the spacecraft.

To see what’s under the cloud tops, MWR will measure the microwave radiation emitted from inside the planet. The planet emits radiation across the radio, microwave and infrared ranges, but only microwave frequencies can make it out through the thick clouds. The depth from which the radiation can escape depends on frequency, so by measuring different frequencies of microwave radiation, MWR can study different layers of Jupiter’s interior.

Strong radio emission from Jupiter's radiation belts blocks our view of the planet from Earth at the critical microwave frequencies necessary to measure Jupiter's water abundance. Juno avoids this problem by flying close to Jupiter, inside the radiation belts.

MWR consists of six antennas designed to passively sense the microwaves coming from six levels within the clouds. These levels range from the cloud tops, where the pressure is about the same as that on Earth, down to a depth of hundreds of miles, where the pressure is a thousand times greater. The deepest layers (below 100 bars) will reveal Jupiter’s water content, which is key to understanding how Jupiter formed. MWR will also allow us to determine how deeply atmospheric features extend into the planet, including the cloud bands and the Great Red Spot.

All six MWR antennas are located on the sides of Juno’s hexagonal body, with the largest antenna taking up one whole side. Each antenna is connected by a cable to a receiver, which sits in the instrument vault on top of the spacecraft.

The MWR instrument operates during five preselected Juno orbits. During these orbits, Juno is oriented so that the MWR antennas' views sweep across Jupiter directly below the spacecraft. This geometry allows Juno to observe thermal emission from each point along the spacecraft's path over the planet to be observed from multiple angles, helping MWR build up a three- dimensional understanding of how the deep atmosphere is structured.

The largest of Juno's six MWR antennas takes up a full side of the spacecraft.

JPL provided the MWR sub-system components, including the antennas and receivers.

Instrument stats: Measures microwave brightness temperatures of Jupiter with six passive microwave antennas, sensitive to wavelengths between 1.3 centimers and 50 centimeters, or frequencies between 0.6 GHz and 22 GHz

Largest antenna is 5.2 feet (1.6 meters) square.

Location: Two sides of the spacecraft, between the solar arrays

Two largest antennas, which sense the lowest frequencies, are "patch arrays," the next three smaller antennas are "slot arrays," the smallest is a "horn" antenna.

Gravity Science Experiment Juno's Gravity Science experiment will use the spacecraft's telecommunications system to help us understand Jupiter’s inner structure, by very precisely mapping the planet's gravitational field. The Gravity Science experiment will enable Juno to measure Jupiter’s gravitational field and reveal the planet’s internal structure. Juno will see how the material inside Jupiter churns and flows, helping to determine whether the planet harbors a dense core at its center.

Variations in Jupiter’s inner structure will have tiny effects on its gravitational field, which ever so slightly alters Juno’s orbit. The closer Juno gets to Jupiter, the more pronounced the displacements are. These subtle shifts in Juno’s motion cause equally subtle shifts in the frequency of a radio signal received from and sent back to Earth. Known as the Doppler effect, it’s the same type of frequency shift that happens when the pitch of an ambulance’s siren increases when speeding toward you and decreases when speeding away from you.

To measure these tiny shifts, Juno’s telecommunication system is equipped with a radio transponder that operates in the X band, which are radio signals with a wavelength of three centimeters. The transponder detects signals sent from NASA’s Deep Space Network on Earth and immediately sends a signal in return. The small changes in the signal’s frequency tell us how much Juno has shifted due to variations in Jupiter’s gravity. For added accuracy, the telecommunication system also has a Ka- band translator system, which does a similar job, but at radio wavelengths of one centimeter. One of the antennas of NASA's Deep Space Network located in Goldstone, California, has been fitted to send and receive signals at both radio bands. An instrument called the Advanced Water Vapor Radiometer helps to isolate the signal from interference caused by Earth’s atmosphere.

JPL provided the Juno telecom system. The Italian Space Agency contributed the Ka-band translator system.

The Doppler shift in Juno's radio signal will allow scientists to map variations in Jupiter's gravity field as the spacecraft falls past the planet during each orbit.

Instrument stats: Frequencies used for transmitting gravity data:X-band and Ka-band

Location: Saucer-shaped high-gain antenna on top of spacecraft and radio transponder within radiation vault

Magnetometer Experiment (MAG) Juno's magnetometer will visualize Jupiter's magnetic field in 3-D, all around the planet, sensing the deep interior and watching for changes over time.

Using its magnetometer (MAG), Juno will create an extremely accurate and detailed three-dimensional map of Jupiter’s magnetic field. This unprecedented study will allow us to understand Jupiter’s internal structure and how the magnetic field is generated by the dynamo action inside – the churning of electrically charged material deep below the surface. MAG will also monitor the field for long-term variations, called secular variations, during the entire mission. Measurements of these variations, in combination with the map, will help us determine the depth of the dynamo region. Because Jupiter lacks a rocky crust or continents that complicate the picture as they do at Earth, Juno’s observations could be the most detailed look at a planetary dynamo ever.

Juno's two magnetometers are located on a boom at the end of one of its long solar arrays.

Electrical currents can align themselves with the magnetic field, and these so-called Birkeland currents help drive the brilliant auroras around Jupiter’s poles. To better understand the auroras, MAG will measure these currents.

MAG consists of two flux gate magnetometers, which will measure the strength and direction of the magnetic field lines, and an advanced stellar compass (ASC) -- a system of four star cameras that will monitor the orientation of the magnetometer sensors.

Juno’s other instruments have their own small magnetic fields, and to avoid contamination, the MAG sensors sit as far from the rest of the spacecraft as possible. They are mounted on the magnetometer boom that sticks out from one of Juno’s solar arrays. As an extra precaution, there are two sets of MAG sensors – one 33 feet (10 meters) from the center of the spacecraft and one 39 feet (12 meters) from the center. By comparing measurements from both sensors, mission scientists can remove from the MAG data any contamination due to the spacecraft itself.

NASA's Goddard Space Flight Center provided the Juno magnetometers. The ASC is provided by Danish Technical University.

Four star tracker cameras help determine the precise orientation of the magnetometers as they sense Jupiter's magnetic field.

Instrument stats: Sensors: 2 fluxgate magnetometers, plus four advanced star tracker cameras

Location: Mounted on a boom at the end of one of Juno's solar arrays

Jovian Auroral Distributions Experiment (JADE) JADE is a set of sensors charged with detecting the electrons and ions that produce Jupiter’s auroras.

The JADE instrument will work with some of Juno’s other instruments to identify the particles and processes that produce Jupiter’s stunning auroras. It will also help create a three-dimensional map of the planet’s magnetosphere.

JADE consists of four sensors that share an electronics box. Three of the sensors will detect electrons in the space surrounding Juno, while the fourth will identify positively charged hydrogen, helium, oxygen and sulfur ions. Most of these ions are ejected from the volcanoes on Jupiter’s moon Io.

When Juno flies directly over Jupiter's auroras, JADE will be able to observe the light show, resolving structures as small as 50 kilometers (30 miles). Considering that the auroras can stretch for tens of thousands of kilometers around the pole, JADE will be able to discern a lot of detail. JADE will also measure the particles that fly to and from Jupiter’s poles, spiraling along as they’re guided by the magnetic field.  JADE is provided by SwRI.

The JADE investigation has two types of sensors to detect the charged particles that create Jupiter's stunning auroras: one for ions and one for electrons.

Instrument stats: Number of sensors: 4 (3 electron sensors, 1 ion sensor)

Location: upper spacecraft deck

Measures electrons in the energy range from 100 eV to 95 keV

Measures ions in the energy range from 10 eV to 46 keV

Jupiter Energetic-Particle Detector Instrument (JEDI) JEDI will measure the energetic particles that stream through space and study how they interact with Jupiter’s magnetic field.

The Jupiter Energetic Particle Detector Instrument (JEDI) will measure energetic particles that stream through space around Jupiter, studying how they interact with Jupiter’s magnetic field. These electrically charged particles -- consisting of electrons and ions -- follow the influence of the magnetic field. Many of them are channeled by the field toward Jupiter’s poles, where they crash into the atmosphere and create brilliant auroras.

Each of the three JEDI detectors consists of a disk the size and shape of a hockey puck attached to an electronics box.

JEDI will determine the amount of energy these particles carry, their type and the direction in which they’re zipping around Jupiter. Working with Juno’s other instruments designed to study the magnetosphere -- the bubble created by Jupiter’s magnetic field -- JEDI will help us understand how the planet's auroras are produced, as well as the processes by which the magnetic field interacts with charged particles to dump energy into the planet’s atmosphere. 

JEDI comprises three identical sensor units each with six ion and six electron views. JEDI works in close coordination with the JADE instrument. JEDI measures the higher-energy charged particles in Jupiter's environment, while JADE measures the lower-energy ones. The instrument also works in coordination with the JADE and Waves instruments to investigate Jupiter’s polar space environment, with a particular focus on the physics of Jupiter’s intense and impressive northern and southern auroral lights.

JEDI uses measurement techniques and technologies demonstrated previously at Jupiter by NASA’s Galileo mission, and is similar to the New Horizons Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI).

JEDI is provided by APL.

Instrument stats: Number of sensors: 3

Location: Upper spacecraft deck

Measures electrons in the energy range of 25 keV to 800 keV

Measures ion in the energy range of 10 keV to 8000 keV

Jovian Infrared Auroral Mapper (JIRAM) JIRAM will provide a visual and thermal (infrared) view of Jupiter’s aurora.

JIRAM will study Jupiter's atmosphere in and around Jupiter's auroras, providing new insights about the interactions between the auroras, the magnetic field and the magnetosphere. JIRAM will be able to probe the atmosphere down to 30 to 45 miles (50 to 70 kilometers) below the cloud tops, where the pressure is five to seven times greater than on Earth at sea level.

JIRAM consists of a camera and a spectrometer, which splits light into its component wavelengths, like a prism. The camera will take pictures in infrared light, which is heat radiation with wavelengths of two to five microns (millionths of a meter) -- three to seven times longer than visible wavelengths. In particular, the instrument will snap photos of auroras at a wavelength of 3.4 microns -- the wavelength of light emitted by excited hydrogen ions in the polar regions. Methane in the atmosphere absorbs light at this same wavelength, darkening the atmosphere behind the auroras. In front of a darkened background, the auroras stand out even more brightly.

JIRAM is an infrared spectrometer designed to observe Jupiter's auroras and atmosphere from very close to the planet.

The instrument will also try to learn about the structure and origin of voids in Jupiter’s atmosphere called hot spots. These spots -- like the one the Galileo probe happened to have dropped into in 1995 -- are windows into the depths of Jupiter’s atmosphere. By measuring the heat radiating from Jupiter’s atmosphere, JIRAM can determine how water-containing clouds circulate under the surface. It turns out that this sort of motion, called convection, in which hot gas rises and cool gas sinks, reveals the amount of water in these clouds. Certain gases in the atmosphere -- methane, water, ammonia and phosphine, in particular -- absorb particular wavelengths of infrared light. When the spectrometer measures the infrared rainbow emitted by Jupiter, the wavelengths of light absorbed by those gases will be reduced by an amount that indicates the chemical composition of the atmosphere.

JIRAM was developed by the Italian National Institute for Astrophysics and funded by the Italian Space Agency. 

The JIRAM instrument is mounted to the aft deck of the Juno spacecraft and looks in the same direction as the other optical instruments, UVS and JunoCam.

Instrument stats: Spectral range: Sensitive to infrared wavelengths between 2 and 5 microns.

Spectral resolution: 9 nanometers

Location: Mounted to the aft deck of the spacecraft

Operating temperature: 100 Kelvin or lower

Ultraviolet Imaging Spectrograph (UVS) UVS will see Jupiter’s auroras in UV, which helps us understand Jupiter’s upper atmosphere and the particles that slam into it, creating the greatest light show in the solar system.

UVS will take pictures of Jupiter’s auroras in ultraviolet light. Working with Juno’s JADE and JEDI instruments, which measure the particles that create the auroras, UVS will help us understand the relationship between the auroras, the particles that collide with Jupiter's atmosphere to create them, and the planet's magnetosphere as a whole.

NASA’s Hubble Space Telescope has taken impressive images of Jupiter’s auroras, but Juno will get an even better view -- looking directly down on them over the north and south poles. UVS includes a scan mirror for targeting specific auroral features. The instrument is sensitive to both extreme and far-ultraviolet light, within a wavelength range of about 70 to 200 nanometers. In comparison, visible light has wavelengths that range from 400 to 700 nanometers.

Southwest Research Institute (SwRI) provided the UVS instrument. CSL/BELSPO (Belgium) contributed the scan mirror. 

The UVS instrument observes Jupiter's auroras in ultraviolet light, breaking up the light into its component wavelengths to reveal processes that power the planet's brilliant UV light show.

Instrument stats: Wavelength range: 68 to 210 nanometers

Spectral resolution: 0.6 to 1.2 nanometers

Location: Mounted to side of spacecraft, between solar arrays

Waves The Waves instrument will measure radio and plasma waves in Jupiter’s magnetosphere, helping us understand the interactions between the planet's magnetic field, atmosphere and magnetosphere. Waves will also pay particular attention to activity associated with auroras. 

Jupiter's magnetosphere, an enormous bubble created by the planet's magnetic field, traps plasma, an electrically charged gas. Activity within this plasma, which fills the magnetosphere, triggers waves that only an instrument like Waves can detect.

Waves consists of two sensors that monitor radio and plasma waves in echoing through Jupiter's magnetosphere.

Because plasma conducts electricity, it behaves like a giant circuit, connecting one region with another. Activity on one end of the magnetosphere can therefore be felt somewhere else, allowing Juno to monitor processes occurring in this entire, giant region of space around Jupiter. Radio and plasma waves move through the space around all of the giant, outer planets, and previous missions have been equipped with similar instruments.

Juno's Waves instrument consists of two sensors; one detects the electric component of radio and plasma waves, while the other is sensitive to just the magnetic component of plasma waves. The first sensor, called an electric dipole antenna, is a V-shaped antenna, four meters from tip to tip -- similar to the rabbit-ear antennas that were once common on TVs. The magnetic antenna -- called a magnetic search coil -- consists of a coil of fine wire wrapped 10,000 times around a 6-inch-long (15-centimeter) core. The search coil measures magnetic fluctuations in the audio frequency range. 

The University of Iowa provides the instrument. 

This artist's rendering shows Juno above Jupiter's north pole, with the auroras glowing brightly. Jupiter's magnetic field surrounds the planet. A radio wave from the auroras is shown traveling past the spacecraft, where it is intercepted by the Waves investigation, whose sensors are highlighted in bright green.

Instrument stats: Sensors: 2 (electric dipole antenna and magnetic search coil)

Frequency range: 50 Hz (near the bottom of the audio frequency range) to ~40 MHz (the limit of Jupiter's radio emissions)

JunoCam JunoCam is Juno's color imaging camera, which will provide close-up views of Jupiter's poles for the first time. 

Juno’s color, visible-light camera, called JunoCam, is designed to capture remarkable pictures of Jupiter’s cloud tops. As Juno’s eyes, it will provide a wide view, helping to provide context for the spacecraft’s other instruments. JunoCam was included on the spacecraft specifically for purposes of public engagement; although its images will be helpful to the science team, it is not considered one of the mission's science instruments.

Juno rotates twice per minute, so JunoCam's images would be smeared if it were to try to take a complete picture at once. Instead, it is a "push-broom imager," taking thin strips of an image at the same rate that the spacecraft spins. JunoCam then stitches the strips together to form the full picture. 

JunoCam consists of a camera head and an electronics box (the box is housed in Juno's protective radiation vault).

JunoCam takes images mainly during closest approach – about 3,100 miles (5,000 kilometers) above the cloud tops – when it has the best-possible vantage point. Taking pictures with a resolution of up to 25 kilometers (16 miles) per pixel, the wide-angle camera will provide high-quality views of Jupiter’s atmosphere. These images will be made available on the Juno mission website for members of the public to process into color views. The public will also help choose targets for JunoCam to image, and members of the amateur astronomy community will provide maps to help in image planning.

The Juno team expects that high-energy particles surrounding Jupiter will eventually damage JunoCam’s electronics to a point where the instrument will have to be shut down permanently. The camera is designed to last for at least seven orbits – enough time to take many pictures. 

JunoCam’s hardware is based on a descent camera, called MARDI, that was developed for NASA's Curiosity Mars rover. Some of its software was originally developed for NASA’s Mars Odyssey and Mars Reconnaissance Orbiter spacecraft. JunoCam is provided by Malin Space Science Systems.

JunoCam is shown mounted to the spacecraft, prior to launch.

Instrument stats: Image field of view: 58 degrees; 0.7 mrad/pixel

Spectral range: 400-900 nanometers

Spectral filters: 3 RGB color, 1 methane [878-899 nanometers])

Location: Side of spacecraft

Image size: 1600 x 4800 pixel 3-color image; 800 x 2400 pixel methane-band image

Juno Science Team

Scott Bolton, principal investigator, Southwest Research Institute, San Antonio

John "Jack" Connerney, deputy principal investigator, Goddard Space Flight Center, Greenbelt, Maryland

Steve Levin, project scientist, NASA’s Jet Propulsion Laboratory, Pasadena, California

This map shows some key Juno mission partners across the U.S. and Europe. Credit: NASA/JPL-Caltech

Instrument Leads

Michael Janssen, MWR Instrument Lead, Jet Propulsion Laboratory, Pasadena, California

John Connerney, MAG Instrument Lead, Goddard Space Flight Center, Greenbelt, Maryland

Phil Valek, JADE Instrument Lead, Southwest Research Institute, San Antonio

William Folkner, Gravity Science Investigation Lead, Jet Propulsion Laboratory, Pasadena, California

Barry Mauk, JEDI Instrument Lead, Johns Hopkins University/Applied Physics Laboratory, Laurel, Maryland

William Kurth, Waves Instrument Lead, University of Iowa, Iowa City

Randy Gladstone, UVS Instrument Lead, Southwest Research Institute, San Antonio

Michael Ravine, JunoCam Instrument Lead, Malin Space Science Systems, San Diego

Alberto Adriani, JIRAM Instrument Lead, Italian Space Agency, Rome

Co-Investigators

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410 years ago: galileo discovers jupiter’s moons, johnson space center.

Peering through his newly-improved 20-power homemade telescope at the planet Jupiter on Jan. 7, 1610, Italian astronomer Galileo Galilei noticed three other points of light near the planet, at first believing them to be distant stars. Observing them over several nights, he noted that they appeared to move in the wrong direction with regard to the background stars and they remained in Jupiter’s proximity but changed their positions relative to one another. He later observed a fourth star near the planet with the same unusual behavior. By Jan. 15, Galileo correctly concluded that they were not stars at all but moons orbiting around Jupiter, providing strong evidence for the Copernican theory that most celestial objects did not revolve around the Earth. In March 1610, Galileo published his discoveries of Jupiter’s satellites and other celestial observations in a book titled Siderius Nuncius (The Starry Messenger) .

As their discoverer, Galileo had naming rights to Jupiter’s satellites. He proposed to name them after his patrons the Medicis and astronomers called them the Medicean Stars through much of the seventeenth century, although in his own notes Galileo referred to them by the Roman numerals I, II, III, and IV, in order of their distance from Jupiter. Astronomers still refer to the four moons as the Galilean satellites in honor of their discoverer. The German astronomer Johannes Kepler suggested naming the satellites after mythological figures associated with Jupiter, namely Io, Europa, Ganymede, and Callisto, but his idea didn’t catch on for more than 200 years. Scientists didn’t discover any more satellites around Jupiter until American astronomer E.E. Barnard found Jupiter’s fifth moon Amalthea in 1892, much smaller than the Galilean moons and orbiting closer to the planet than Io. It was the last satellite in the solar system found by visual observation – all subsequent discoveries occurred via photography or digital imaging. As of today, astronomers have identified 79 satellites orbiting Jupiter.

Although each of the Galilean satellites has unique features, such as the volcanoes of Io, the heavily cratered surface of Callisto, and the magnetic field of Ganymede, scientists have focused more attention on Europa due to the tantalizing possibility that it might be hospitable to life. In the 1970s, NASA’s Pioneer 10 and 11 and Voyager 1 and 2 spacecraft took ever increasingly detailed images of the large satellites including Europa during their flybys of Jupiter. The photographs revealed Europa to have the smoothest surface of any object in the solar system, indicating a relatively young crust, and also one of the brightest of any satellite indicating a highly reflective surface. These features led scientists to hypothesize that Europa is covered by an icy crust floating on a subsurface salty ocean. They further postulated that tidal heating caused by Jupiter’s gravity reforms the surface ice layer in cycles of melting and freezing. 

More detailed observations from NASA’s Galileo spacecraft that orbited Jupiter between 1995 and 2003 and completed 11 close encounters with Europa revealed that long linear features on its surface may indicate tidal or tectonic activity. Reddish-brown material along the fissures and in splotches elsewhere on the surface may contain salts and sulfur compounds transported from below the crust and modified by radiation. Observations from the Hubble Space Telescope and re-analysis of images from Galileo revealed possible plumes emanating from beneath Europa’s crust, lending credence to that hypothesis. While the exact composition of this material is not known, it likely holds clues to whether Europa may be hospitable to life. 

Future robotic explorers of Europa may answer some of the outstanding questions about this unique satellite of Jupiter. Set for launch in 2025, NASA’s planned Europa Clipper mission will enter orbit around Jupiter and conduct 45 flybys of Europa during its 3.5-year mission. Managed by the Jet Propulsion Laboratory in Pasadena, California, and the Applied Physics Laboratory at Johns Hopkins University in Baltimore, Maryland, Europa Clipper will carry nine instruments including imaging systems and a radar to better understand the structure of the icy crust. Although the European Space Agency’s JUICE (Jupiter Icy Moon Explorer) spacecraft’s main goal will be to enter orbit around Ganymede in the 2020s, it also plans to conduct studies of Europa complementary with Europa Clipper’s. The two spacecraft should greatly increase our understanding of Europa.

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• Published: 21 October 2021

A unique hot Jupiter spectral sequence with evidence for compositional diversity

• Megan Mansfield   ORCID: orcid.org/0000-0003-4241-7413 1 , 2 ,
• Michael R. Line   ORCID: orcid.org/0000-0001-6247-8323 3 ,
• Jacob L. Bean 4 ,
• Jonathan J. Fortney 5 ,
• Vivien Parmentier 6 ,
• Lindsey Wiser   ORCID: orcid.org/0000-0002-3295-1279 3 ,
• Eliza M.-R. Kempton   ORCID: orcid.org/0000-0002-1337-9051 7 ,
• Ehsan Gharib-Nezhad 8 ,
• David K. Sing   ORCID: orcid.org/0000-0001-6050-7645 9 ,
• Mercedes López-Morales 10 ,
• Claire Baxter 11 ,
• Jean-Michel Désert 11 ,
• Mark R. Swain 12 &
• Gael M. Roudier   ORCID: orcid.org/0000-0002-7402-7797 12  

Nature Astronomy volume  5 ,  pages 1224–1232 ( 2021 ) Cite this article

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The emergent spectra of close-in, giant exoplanets (‘hot Jupiters’) are expected to be distinct from those of self-luminous objects with similar effective temperatures because hot Jupiters are primarily heated from above by their host stars rather than internally from the release of energy from their formation 1 . Theoretical models predict a continuum of dayside spectra for hot Jupiters as a function of irradiation level, with the coolest planets having absorption features in their spectra, intermediate-temperature planets having emission features due to thermal inversions and the hottest planets having blackbody-like spectra due to molecular dissociation and continuum opacity from the H − ion 2 , 3 , 4 . Absorption and emission features have been detected in the spectra of a number of individual hot Jupiters 5 , 6 , and population-level trends have been observed in photometric measurements 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 . However, there has been no unified, population-level study of the thermal emission spectra of hot Jupiters as there has been for cooler brown dwarfs 16 and transmission spectra of hot Jupiters 17 . Here we show that hot Jupiter secondary eclipse spectra centred around a water absorption band at 1.4 μm follow a common trend in water feature strength with temperature. The observed trend is broadly consistent with model predictions for how the thermal structures of solar-composition planets vary with irradiation level, but is inconsistent with the predictions of self-consistent one-dimensional models for internally heated objects. This is particularly the case because models of internally heated objects show absorption features at temperatures above 2,000 K, whereas the observed hot Jupiters show emission features and featureless spectra. Nevertheless, the ensemble of planets exhibits some degree of scatter around the mean trend for solar-composition planets. The spread can be accounted for if the planets have modest variations in metallicity and/or elemental abundance ratios, which is expected from planet formation models 18 , 19 , 20 , 21 .

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Data that support this paper’s findings and its plots are available on GitHub at https://github.com/meganmansfield/HSTeclipse . The full model grid can be found at https://www.dropbox.com/sh/gfsmqlxs6l1p0st/AABXyRA9RlZawpsknXc9Ya7ra?dl=0 . Source data are provided with this paper.

Code availability

Software used for this work included batman 44 , emcee 47 , Matplotlib 74 , NumPy 75 , pysynphot 76 and SciPy 77 . All code used to produce findings in this paper is available on GitHub at https://github.com/meganmansfield/HSTeclipse .

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Acknowledgements

The work was based on observations made with the NASA/ESA Hubble Space Telescope that were obtained from the data archive at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. M.M. acknowledges funding from a NASA FINESST grant. M.R.L. acknowledges funding from NSF AST-165220, and NASA NNX17AB56G. M.R.L. also acknowledges opacity information from R. Lupu. M.R.L., J.L.B. and J.J.F. acknowledge funding for this work from STScI grants GO-13467 and GO-14792. J.J.F. and M.R.L. acknowledge the support of NASA grant 80NSSC19K0446. J.-M.D. acknowledges support from the Amsterdam Academic Alliance Program and from the European Research Council European Union’s Horizon 2020 research and innovation programme (grant no. 679633; Exo-Atmos). This work is part of the research programme VIDI New Frontiers in Exoplanetary Climatology with project number 614.001.601, which is (partly) financed by the Dutch Research Council.

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• Megan Mansfield

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School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA

Michael R. Line & Lindsey Wiser

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• Jacob L. Bean

Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA, USA

Jonathan J. Fortney

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Vivien Parmentier

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Contributions

M.M. reduced and analysed the new data sets, led the data–model comparison and wrote the manuscript. M.R.L. created the self-consistent 1D exoplanet model grids and contributed to the writing of the manuscript. J.L.B. contributed to the conception of the population study and the writing of the manuscript. J.J.F. contributed to the interpretation of the results and the writing of the manuscript. L.W. created the self-consistent 1D self-luminous object model grids. V.P., E.M.-R.K., C.B. and J.-M.D. contributed to the interpretation of the results. E.G.-N. generated the opacities and absorption cross-sections for the 1D model grids. D.K.S. and M.L.-M. are principal investigators of the HST program GO-14767 from which we obtained the new observations that were analysed in this work. M.R.S. and G.M.R. contributed to the conception of the population study. All authors commented on the manuscript.

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Correspondence to Megan Mansfield .

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Supplementary Figs. 1–4 and Tables 1–6.

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Source data fig. 1.

.zip archive containing 19 .txt files, each of which contains one of the secondary eclipse spectra displayed in Fig. 1

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.zip archive containing four .txt files. Two of the .txt files contain the data points for hot Jupiters and brown dwarfs shown in Fig. 3. The other two .txt files contain the models for hot Jupiters and self-luminous objects shown in Fig. 3.

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Mansfield, M., Line, M.R., Bean, J.L. et al. A unique hot Jupiter spectral sequence with evidence for compositional diversity. Nat Astron 5 , 1224–1232 (2021). https://doi.org/10.1038/s41550-021-01455-4

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All About Jupiter

Jupiter is a stormy planet that is probably best known for its Great Red Spot. The spot is actually a giant, wild storm that has been raging for more than 300 years. Credit: NASA/JPL-Caltech

Jupiter is the biggest planet in our solar system. It's similar to a star, but it never got massive enough to start burning. It is covered in swirling cloud stripes. It has big storms like the Great Red Spot, which has been going for hundreds of years. Jupiter is a gas giant and doesn't have a solid surface. It is still unclear if deeper down, Jupiter has a central core of solid material or if it may be a thick, super-hot and dense soup. Jupiter also has rings, but they're too faint to see very well.

Explore Jupiter! Click and drag to rotate the planet. Scroll or pinch to zoom in and out. Credit: NASA Visualization Technology Applications and Development (VTAD)

Credit: NASA/JPL-Caltech

Structure and Surface

• Jupiter is the biggest planet in our solar system. It is actually more than twice as massive than the other planets of our solar system combined.
• Jupiter is a gas giant. It is made mostly of hydrogen and helium.
• Jupiter has a very thick atmosphere.
• Jupiter has rings, but they’re very hard to see.
• The giant planet's Great Red Spot is a centuries-old storm bigger than Earth.

Time on Jupiter

• One day on Jupiter goes by in just 10 hours.
• One year on Jupiter is the same as 11.8 Earth years.

Jupiter's Neighbors

• Jupiter has 95 officially recognized moons.
• Jupiter is the fifth planet from the Sun. That means Mars and Saturn are Jupiter’s neighboring planets.

Quick History

• Jupiter has been known since ancient times because it can easily be seen with just our eyes. No special equipment is needed.
• Jupiter has been visited or passed by several spacecraft , orbiters and probes, such as Pioneer 10 and 11, Voyager 1 and 2, Cassini, New Horizons, and Juno.
• Jupiter has auroras , just like Earth! Not only are the auroras huge in size, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease.

What does Jupiter look like?

This striking view of Jupiter's Great Red Spot and turbulent southern hemisphere was captured by NASA's Juno spacecraft as it performed a close pass of the gas giant planet. Credit: Enhanced image by Kevin M. Gill (CC-BY) based on images provided courtesy of NASA/JPL-Caltech/SwRI/MSSS

Astronomers are using NASA's Hubble Space Telescope to study auroras — stunning light shows in a planet's atmosphere — on the poles of the largest planet in the solar system, Jupiter. Credits: NASA, ESA, and J. Nichols (University of Leicester)

This new Hubble Space Telescope view of Jupiter, taken on June 27, 2019, reveals the giant planet's trademark Great Red Spot, and a more intense color palette in the clouds swirling in Jupiter's turbulent atmosphere than seen in previous years. The colors, and their changes, provide important clues to ongoing processes in Jupiter's atmosphere. Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)

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Hypothesis: Our Solar System Lacks 'Super-Earths' Because Jupiter Wrecked Them All

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I’ve always loathed Jupiter.

For one thing, I am not stoked on toxic gases or crushing gravity. And the weather on Jupiter is abysmal, with wind speeds roughly twice those of hurricanes on Earth.

Were I in charge, I once told a theoretical physicist at Vanderbilt University in Nashville, I would set about destroying Jupiter for the good of humanity. He reminded me that in 1994, a like-minded comet smashed into the gas giant, which is some 89,000 miles across. The result was like a bullet fired into a mountain of shaving cream, accomplishing nothing.

Sometimes when I am feeling crabby aboard an overly humid BART car with no vacant seats I think, “Well, of all the places in the universe that I could be right now, at least I’m not on Jupiter.”

I mention this to explain the vindication I feel upon learning that Jupiter may be the reason our solar system is, it’s turning out, something of a weirdo among its galactic peers. Scientists perusing thousands of exoplanets (some potentially habitable) in other systems around the Milky Way are discovering that rocky “super-Earths” are commonplace.

These are planets bigger than our own, albeit perhaps not better for our brand of life: they may have crushingly thick atmospheres, and their orbits are typically tighter than Mercury’s.

“The standard-issue planetary system in our galaxy seems to be a set of super-Earths with alarmingly short orbital periods. Our solar system is looking increasingly like an oddball,” says Gregory Laughlin , professor and chair of astronomy and astrophysics at University of California,  Santa Cruz, and co-author of a new paper in Proceedings of the National Academy of Sciences.

The reason our humble solar system suffers this peculiar dearth of “super-Earths” and must instead make do with our vanilla “ Earth -Earth” can be summarized thusly: Jupiter.

Like Miley Cyrus, Jupiter came in like a wrecking ball.

In 2011, astronomers proposed the “Grand Tack” hypothesis, suggesting that during the early days of the solar system — the first few million years — Jupiter migrated inward toward the sun, stopping only when the formation of Saturn tugged it back out to its current orbit.

Laughlin and co-author Konstantin Batygin think rocky planets could’ve been forming near our sun, until an encroaching Jupiter’s gravitational perturbations rudely started compressing their orbits, slinging them into each other in a chain reaction that took out any nascent super-Earths and sent a lot of debris spiraling into the sun to be vaporized.

“It’s the same thing we worry about if satellites were to be destroyed in low-Earth orbit. Their fragments would start smashing into other satellites and you’d risk a chain reaction of collisions,” Laughlin says. “Our work indicates that Jupiter would have created just such a collisional cascade in the inner solar system.”

A second generation of inner planets including familiar old Earth, as well as Mercury, Venus and Mars, would’ve emerged from the aftermath only tens of millions of years later. This explains why the planets close to our sun are younger than the planets farther away. And again, this was possible only thanks to Saturn tugging Jupiter away, thereby allowing our humble planet some breathing room to, you know, exist.

Thank you, Saturn.

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April 1, 2015

Jupiter, Destroyer of Worlds, May Have Paved the Way for Earth

Careening toward the sun, Jupiter cleared the way for Earth to form—with help from Saturn, too

By Lee Billings &

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In Greco-Roman mythology Jupiter is the king of the gods, a deity who destroyed an older race of titans to become the jealous and vengeful lord of heaven and Earth.   Strange though it may seem, scientific theory lends credence to this historical fiction. As the largest, heaviest object orbiting our sun, Jupiter’s namesake world is the lord of planets, a dominant force in the solar system. Eons ago, while flinging leftover debris from planetary formation out of our solar system, Jupiter probably also tossed some down toward our primordial globe, delivering some of the water that now fills our oceans. Jupiter still shepherds swarms of asteroids, occasionally sending some whizzing harmlessly into interstellar space or on destructive collision courses with Earth and other planets. Jupiter may have even played a role in the asteroid-linked extinction of the dinosaurs about 66 million years ago, an event that ushered in the reign of our mammalian ancestors. Without Jupiter, humans might not exist.   A new study, however, suggests that without Jupiter, Earth itself might not exist either. Where this and the other rocky planets now orbit there may have first been a previous generation of worlds destined to be bigger, gas-shrouded, utterly uninhabitable orbs. But Jupiter came swinging in, clearing the way for small worlds like Earth by destroying those older planets. The study , co-authored by California Institute of Technology planetary scientist Konstantin Batygin and University of California, Santa Cruz, astrophysicist Greg Laughlin, appeared in the March 23 Proceedings of the National Academy of Sciences .   A hole in the solar system There are hundreds of reasons to suspect that our solar system used to have more and bigger inner planets—the hundreds of multiplanetary systems discovered by planet-hunting projects such as NASA’s Kepler mission. Although our solar system is essentially empty inward of Mercury, equivalent regions around most other stars appear to be packed with close-in, intermediate-mass planets—those between the size of Earth and Neptune. Hopeful astronomers have dubbed these worlds “super-Earths” but most of them seem to be more like hydrogen-rich, gas-shrouded mini-Neptunes—very unearthly indeed. “Now that we can look at our own solar system in the context of all these other planetary systems,” Laughlin says, “the standard-issue planetary system in our galaxy seems to be a set of super-Earths with alarmingly short orbital periods. Our solar system is looking increasingly like an oddball.”   If so, the obvious question is how it got that way. According to Batygin, there’s no reason to suspect that the actual process of planet formation occurred very differently around our sun than around other stars. Instead, the explanation for our solar system’s outlier status may be found in the details of its subsequent evolution—controlled to a remarkable degree by Jupiter.   Migrating worlds Astronomers used to consider planetary systems reasonably static and stable. Planets would coalesce out of the swirling disks of gas and dust around young stars, a bit like trees springing up from dirt, putting down roots and scarcely budging from where they were born. Small, rocky planets would form in the intense light and heat close to stars, whereas gas-giant planets would form farther out, where cold temperatures preserved more gassy feedstock. Small or large, gassy or rocky, most planets would move about their stars in pristine, near-circular orbits. All this cohered with our understanding of our own solar system. But we may have been wildly mistaken about what is the norm.   Twenty years ago when astronomers found the first planets orbiting other stars, they also began realizing that planetary systems are chaotic places. Some planets did not orbit in near-circles but in oblong “eccentric” paths that took them swinging close and then far from their stars—almost as if they had been thrown off-kilter by the gravitational influence of other worlds. And most of the newfound giant planets were very different than Jupiter—in scorching, star-hugging orbits far inward from the cold outer regions where they must have formed. Planets could migrate, too, propelled by gentle interactions with their formative disks or by close encounters with their planetary siblings.   Ever since those discoveries researchers have been grappling with the idea of planetary migration to better understand not only the features of other planetary systems, but our own. One example is the “grand tack” scenario, which posits that in the first few million years of our solar system’s existence Jupiter migrated into and then back out of the inner solar system, following a course similar to a sailboat’s when it tacks around a buoy. Back then Jupiter would have still been embedded in a gas-rich disk. Much of that gas was spiraling down toward the sun—so much that the action would have sapped some of Jupiter’s angular momentum, too, causing the giant planet itself to spiral in to the vicinity of where Mars is today. Jupiter would have kept falling in toward the sun if not for being caught by the subsequent formation of Saturn, which began drifting in as well. As the two giant planets came closer together, they were caught  in an orbital resonance. This resonance expelled all the gas between them, gradually reversing their death spirals and causing them to “tack” back out to the outer solar system.   As outlandish as it seems, the physical mechanisms underlying the grand tack hypothesis are sound and there are good reasons to suspect it took place. The scenario neatly explains Mars’s anomalously small size, which theorists believe should be larger, given how much planet-forming material should have existed long ago in its orbit. In the grand tack Jupiter would have ejected most of that material, leaving behind just enough for Mars to form. The hypothesis also helps explain the distribution of icy and rocky bodies in the Asteroid Belt and various other features of the solar system.   The grand attack In their study Batygin and Laughlin investigated whether Jupiter’s grand tack could explain the gaping hole at the heart of our solar system, too. Using numerical simulations, the duo examined what the grand tack would do to a hypothetical embryonic population of super-Earths caught in mid-formation. The simulations suggested that Jupiter’s inward spiral would send swarms of 100-kilometer-wide planetary building blocks cascading into the inner solar system. The giant planet’s gravity would also sling those building blocks and the inner planets themselves into overlapping, elliptical orbits, creating an interplanetary demolition derby of whirling, colliding fragmenting worlds. “It’s the same thing we worry about if satellites were to be destroyed in low Earth orbit,” Laughlin says. “Their fragments would start smashing into other satellites and you’d risk a chain reaction of collisions. Our work indicates that Jupiter would have created just such a collisional cascade in the inner solar system.”   Although these collisions would have been spectacularly violent, they could not by themselves entirely destroy the coalescing super-Earths. Instead, the avalanche of debris from the collisions would have raised powerful aerodynamic headwinds in the surrounding solar system disk, forming spiraling swirls of gas that then swept the first generation of inner rocky planets down into the sun. “It’s a very effective physical process,” Batygin says. “You only need a few Earth masses worth of material to drive tens of Earth masses worth of planets into the sun.”   Beyond observations of other planetary systems suggesting that ours is an outlier, there is scant evidence that our sun formed and lost an earlier generation of inner worlds. But Laughlin finds the technical strength and sweetness of the idea compelling. “This kind of theory, where first this happened and then that happened, is almost always wrong, so I was initially skeptical,” he says. “But it actually involves generic processes that have been extensively studied by other researchers…. Jupiter’s ‘grand tack’ may well have been a ‘grand attack’ on the original inner solar system.”   A lonelier planet After Jupiter’s grand attack, only whiffs of volatile gas and dregs of shattered rock would remain, but Batygin notes that only about 10 percent of the total material Jupiter may have injected into the inner solar system would have been required to form Mercury, Venus, Earth and Mars. As Jupiter reversed its course and spiraled back to the outer solar system, its passage could have settled a fraction of the dregs into more circular orbits. Across a span of one hundred million to two hundred million years those meager, volatile-depleted dregs would then glom together to make the relatively small and arid inner planets we know today. All this is consistent with a wealth of other evidence suggesting the inner rocky planets formed significantly later than the outer giants, and explains why the sun’s inner worlds are smaller and have thinner atmospheres than those observed around other stars.   The picture that emerges is that we may be even more cosmically alone than previously appreciated. “One of the predictions of our theory is that truly Earth-like planets, with solid surfaces and modest atmospheric pressures, are rare,” Laughlin says.   If true, Batygin and Laughlin’s study would mean that the vast majority of close-in, potentially rocky and habitable planets we now observe around so many other stars may not turn out to be rocky or habitable at all. Instead, visiting them you’d be crushed, cooked and smothered beneath their thick hydrogen-rich atmospheres. The study also suggests that far-out Jupiters are very uncommon around other stars; rather than only briefly visiting inner systems, most giant planets would migrate there to stay, potentially precluding the formation of Earth-like worlds.   In this view, it may really be Saturn that we must thank for being here, because the Ringed Planet’s existence may have kept Jupiter from settling closer to the sun. Which, with poetic license, brings us back to mythology—where Saturn was Jupiter’s father as well as the god responsible for Earth’s wealth, pleasure and plenty. Next time you look up at the heavens, uncrushed and uncooked beneath a clear, hydrogen-free sky, don’t thank your lucky stars—thank Jupiter and Saturn.

The Nine Planets

Jupiter Facts

Jupiter is a massive planet, twice the size of all other planets combined and has a centuries-old storm that is bigger than earth..

Jupiter is the fifth planet from the Sun and the largest planet of the Solar System . It is the oldest planet of the Solar System thus it was the first to take shape out of the remains of the solar nebula.

Key Facts & Summary

• Since it is the fourth brightest object in the sky, Jupiter was observed since ancient times and thus no one can be credited for its discovery. However, the first telescopic observations were conducted by Galileo Galilei in 1609 and in 1610 Galileo also discovered the major moons of Jupiter, but of course not the smaller ones.
• Since many cultures observed Jupiter, they all gave it different names but the Roman name remained used in the majority of cultures. Jupiter is named after the principal Roman god, the equivalent of the Greek god Zeus.
• Jupiter is one of the five visible planets (Mercury, Venus, Mars , Saturn), being the fifth most distant from the Sun at an average distance of 5.2 AU, its closest approach is at 4.9 AU and at its farthest 5.4 AU. Its exact position can be checked online since the planet is constantly tracked.
• It is the biggest planet of the Solar System, with a mean radius of 43.440 miles / 69.911 km, a diameter at the equator of about 88.846 mi / 142.984 km, and at the poles, the diameter is only 83.082 mi / 133.708 km.
• Jupiter is also twice as massive as all the other planets combined, having 318 times the mass of Earth.
• The gas giant has a gravity of 24.79 m/s², a little more than twice of Earth. Its powerful gravity has been used to hurl spacecraft into the farthest regions of the solar system.
• Jupiter rotates once every 10 hours – A Jovian day - thus it has the shortest day of all the planets in the solar system.
• A Jovian year is about 12 Earth years, quite long in comparison to its short days.
• Since Jupiter has a small axial tilt of only 3.13 degrees, it has little seasonal variations.

Jupiter does not have a solid surface being comprised mostly out of swirling gases and liquids such as 90% hydrogen, 10% helium – very similar to the sun.

• A very small fraction of the atmosphere is made up of compounds such as ammonia, sulfur, methane, and water vapor. Jupiter’s atmosphere is the largest planetary atmosphere in the solar system . It makes up almost the entire planet.
• It holds a unique place in the history of space exploration since after it was observed through the telescope, some of its moons were also discovered and because of this, their movements were observed thus ending the belief that everything orbited the Earth.
• Though it remains the biggest planet, Jupiter has been dethroned as the moon king by Saturn, which now has 82 moons. Jupiter currently has only 79 known satellites.
• Among these satellites, four of them are quite famous: Io – for its volcanic activity, Ganymede – for its size, being the largest known moon of any planet, Europa – for hosting favorable conditions to find present-day environments suitable for some form of life beyond Earth, and Callisto – that may also host a subsurface ocean. They are known as the Galilean moons.
• Jupiter has 3 ring systems though they are fainter and smaller than Saturn’s. They are mostly made up of dust and small rocky pieces.
• It has a very strong magnetosphere, almost 20 times stronger than Earth’s magnetic field and 20.000 times larger.
• As a result, the aurora of Jupiter is stronger as well. It produces almost a million Megawatts – Earth’s aurora produces about 1.000 Megawatts.
• A distinct feature of Jupiter is its Great Red Spot – a persistent high-pressure region in the atmosphere that produces an anticyclonic storm, the largest in the solar system. It has been observed since 1830, and it is active for hundreds of years. It is also shrinking.
• Jupiter is surrounded by a plasma torus, produced by its strong magnetic field. It is a field of extremely charged particles making it difficult for a spacecraft to approach the planet, yet some zones are a bit safer. The charged particles also come from Io’s volcanic activity.
• The combination of the powerful magnetic field and the charged particles in the plasma torus creates the brightest auroras in the solar system. Sadly, they can only be seen through ultraviolet.
•  It is now known if Jupiter has a core and recent analysis suggests that the atmosphere extends up to 3.000 km / 1.864 mi down, and beneath this is an ocean of metallic hydrogen going all the way down to the center. About 80-90% of its radius is now believed to be a liquid or technically, an electrically conducting plasma, maybe similar to liquid mercury.

Jupiter is the fourth brightest object in the sky, visible to the naked eye. It shines so brightly that even Venus dims in comparison. Because of this, it has been observed since ancient times by many different cultures. The discovery of Jupiter cannot be attributed to someone.

However, Galileo Galilei is the first astronomer to have observed Jupiter through his telescope.  He began extensive observations of the planet in 1609. During this time and until 1610, Galileo discovered the four largest moons that orbit Jupiter: Io, Europa, Ganymede, and Callisto. They are called the Galilean moons in his honor.

He first thought of them as “fixed stars” but over time he witnessed that the objects changed positions, and he even almost correctly deduced their periods. This discovery was revolutionary since, at the time, most of Europe still endorsed the theory that all the planets orbited Earth.

Galileo’s discovery paved the way for the heliocentric model of the solar system, in which the planets orbit the Sun . Jupiter was known to the Babylonians as Marduk, the patron deity of the city of Babylon. The Romans called it “the star of Jupiter” - as they believed it to be sacred to the principal god of Roman mythology, whose name comes from the Proto-Indo-European vocative compound * Dyēu-pəter.

Jupiter is the counterpart to the mythical Greek king of the gods, Zeus, this name is retained even now in the modern Greek language. The ancient Greeks used to call Jupiter, Phaethon, which means “blazing star.” As supreme god of the Roman pantheon, Jupiter was the god of thunder, lightning, and storms, and appropriately called the god of light and sky.

Throughout the universe, there are many planetary systems similar to ours. Most of them contain terrestrial planets like our own and gas giants like Jupiter. However, they also contain super-Earths – planets that are several times more massive than Earth.

This indicates that our own Solar System should also have these types of planets and it is hypothesized that we did have them but they collided with Jupiter in the early formation of the Solar System. This resulted in Jupiter’s migration from the inner solar system to the outer solar system and thus allowed the inner solar planets to form. This theory is called the Grand Tack Hypothesis.

There are theories that hypothesize the fact that Jupiter may have formed before the Sun while others state that Jupiter formed after the sun about 4.5 billion years ago. Gravity pulled swirling gas and dust and resulted in the creation of Jupiter. Sometime around 4 billion years ago Jupiter settled in its current position in the outer solar system.

Distance, Size and Mass

It is the fifth most distant from the Sun with an average distance of about 5.2 AU. The closest approach is at 4.9 AU and at its farthest 5.4 AU. Its exact position can be checked online since the planet is constantly tracked.

It is the biggest planet of the Solar System, with a mean radius of 43.440 miles / 69.911 km. Almost 11 times bigger than Earth. Jupiter's radius is about 1/10 the radius of the Sun, and its mass is 0.001 times the mass of the Sun, so the densities of the two bodies are similar.

The diameter at the equator of about 88.846 mi / 142.984 km, and at the poles, the diameter is only 83.082 mi / 133.708 km. The average density of Jupiter is about 1.326 g/cm 3, much smaller than all the terrestrial planets.

Jupiter is also 2.5 times more massive than all the other planets combined, having 318 times the mass of Earth. It has a volume of about 1,321 Earths.

Orbit and Rotation

Jupiter rotates once every 10 hours – A Jovian day - thus it has the shortest day of all the planets in the solar system. A Jovian year, on the other hand, is about 12 Earth years, quite long in comparison to its short days. The orbital period is about two-fifths that of Saturn . The orbit of Jupiter is elliptical, inclined about 1.31 degrees when compared to Earth .

The eccentricity of the orbit is about 0.048. This results in its distance from the Sun varying from its perihelion to aphelion by about 75 million km / 46 mi. Jupiter’s upper atmosphere undergoes differential rotation since it’s made out of gases.

Since Jupiter has a small axial tilt of only 3.13 degrees, it has little seasonal variations Because of this low tilt the poles constantly receive less solar radiation than at the planet’s equatorial region.

It is now known if Jupiter has a core and recent analysis suggests that the atmosphere extends up to 3.000 km / 1.864 mi down, and beneath this is an ocean of metallic hydrogen going all the way down to the center. About 80-90% of its radius is now believed to be liquid or technically - electrically conducting plasma – it may be similar to liquid mercury. The Juno mission will reveal more about Jupiter’s inner structure and if indeed it has a core.

The atmosphere of Jupiter is the largest planetary atmosphere in the Solar System, spanning over 5.000 km / 3.000 mi in altitude. It is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide.

The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions sub-divided into lighter-hued zones and darker belts. Because of their interactions, having conflicting circulation patterns, storms and turbulences are created.

Wind speeds of 100 m/s – 360 km/h are common in the zonal jets. The cloud layer is only about 50 km / 31 mi deep, consisting of at least 2 decks of clouds – a thin clearer region and a lower thick one.

The upper atmosphere is calculated to be comprised of about 88-92% hydrogen and 8-12% helium. Since helium atoms have more mass than hydrogen atoms, the composition changes. The atmosphere is thus estimated to be approximately 75% hydrogen and 24% helium with the remaining 1% of the mass consisting of other elements such as methane, water vapor, ammonia, silicon-based compounds, carbon, ethane, oxygen and more.

The outermost layer of the atmosphere contains crystals of frozen ammonia. The interior denser materials by mass are roughly 71% hydrogen, 24% helium and 5% other elements. These atmospheric proportions of hydrogen and helium are close to the theoretical composition of the primordial solar nebula.

Magnetosphere

The magnetic field of Jupiter is fourteen times stronger than that of Earth. It ranges from 4.2 gauss / 0.42 mT at the equator to 10-14 gauss / 1.0 – 1.4 mT at the poles.

This makes Jupiter’s magnetic field the strongest in the Solar System, with the exception of some phenomenon named “sunspots”, that occur on the Sun that are even stronger.

It is believed that the liquid metallic hydrogen present in Jupiter is responsible for this along with the volcanic activity present on Jupiter’s moon Io that emits large amounts of sulfur dioxide forming a gas torus along the moon’s orbit. This gas is ionized in the magnetosphere and through different influences creates a plasma sheet in Jupiter’s equatorial plane. This causes the deformation of the dipole magnetic field into that of a magnetodisk.

As a result, the aurora of Jupiter is stronger as well. It produces almost a million Megawatts – Earth’s aurora, in comparison, produces about 1.000 Megawatts. The combination of the powerful magnetic field and the charged particles from Io in the plasma torus creates the brightest auroras in the solar system. Sadly, most of them can only be seen through ultraviolet.

Because Jupiter is surrounded by this plasma torus, produced by its strong magnetic field, it makes it very difficult for a spacecraft to approach the planet, yet some zones are not so dangerous but the radiation is still present.

Data suggests that the temperature on Jupiter varies from -145 degrees Celsius / -234 degrees Fahrenheit in the clouds too much higher temperatures near the planet’s center. Some estimates concluded that it would get even hotter than the surface of the Sun.

One of the key features of Jupiter is its Great Red Spot. A storm that’s existed since 1831, and possibly since 1665. This oval-shaped object is greater in size than Earth and rotates counterclockwise within a period of six days. Its maximum altitude is about 8 km / 5 mi above the surrounding cloud tops. Since its discovery, it has decreased in size and recent observations state that it decreases in length by about 930 km / 580 mi per year. Storms are common on Jupiter, some are small and last hours while others are huge and last for centuries. Wind speeds of 100 m/s – 360 km/h are common on certain parts of the planet.

Jupiter was the king of the moons since recently, having a total of 79 known satellites. Recently, Saturn dethroned Jupiter having a total of 82 known satellites. These rankings can change as observations continue.

Out of the 79 satellites, 63 are less than 10 km / 6.2 mi in diameter, and have only been observed since 1975. The Galilean moons, Io, Europa, Ganymede, and Callisto are large enough to be seen from Earth with binoculars. They are among the largest satellites discovered in the Solar System with Ganymede being the largest out of all the satellites in our solar system.

Jupiter has both regular moons and irregular moons with further sub-divisions.

Regular moons

The regular moons of Jupiter consists of the Galilean moons and an inner group of 4 small moons with diameters less than 200 km / 124 mi, and orbits with radii less than 200.000 km / 124.274 mi. They all have orbital inclinations of less than half a degree. The Galilean moons orbit between 400.000 and 2.000.000 km – 248.548 mi and 1.242.742 mi. These moons are believed to have been formed together with Jupiter since they have nearly circular orbits near the plane of Jupiter’s equator.

Despite being the largest known satellite in the solar system, it lacks a substantial atmosphere.  It is the 9 th largest object in the solar system with a diameter of 5.268 km / 3.273 mi and is 8% larger than the planet Mercury, although only 45% as massive.

It was named after the mythological cupbearer of the Greek gods, who was kidnapped by Zeus for this purpose. It is the only moon known to have a magnetic field and though it posseses a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System.

Outward from Jupiter, it is the seventh satellite completing an orbit around Jupiter in about 7 Earth days. It is in a 1:2:4 orbital resonance with the moons Europa and Io. It is comprised mostly of equal amounts of silicate rock and water ice, having an iron-rich, liquid core, and an internal ocean that may contain more water than all of Earth’s oceans combined.

A third of its surface is covered by dark regions covered in impact craters and a light region, crosscut by extensive grooves and ridges possibly due to tectonic activity due to tidal heating. It has a thin atmosphere comprised of oxygen, ozone and other elements. There is some speculation on the potential habitability of Ganymede's ocean.

The innermost and third-largest of the four Galilean moons of Jupiter, Io is the fourth-largest moon the solar system with the highest density and the least amount of water molecules of any known astronomical object in the Solar System.

Named after the mythological character Io, a priestess of Hera who became one of Zeus’ lovers, Io is the most geological active object in the Solar system having over 400 active volcanoes.

This extreme geological activity is due to tidal heating caused from friction generated within Io’s interior as it is pulled between Jupiter and the other Galilean moons.

It takes Io 1.77 Earth-days to orbit Jupiter. It is tidally locked to Jupiter, showing only one side to its parent planet, and has a mean radius of 1.131 miles / 1.821 km, slightly larger than Earth’s moon.

Many of Io’s volcanoes produce plumes of 500 km / 300 mi above the surface. More than 100 mountains are uplifted by extensive compression at the base of Io’s silicate crust. Some of these peaks are taller than Mount Everest, the highest point on Earth’s surface.

Io is composed primarily of silicate rock that surrounds a molten iron core. The plains of Io are coated with sulfur and sulfur-dioxide frost. The materials produced by Io’s volcanism make up its thin atmosphere, and result in the large plasma torus around Jupiter.

Europa is the smallest of the four Galilean moons and the sixth largest of all the moons in the Solar System. It was named after the Phoenician mother of King Minos of Crete and lover of Zeus.

It is slightly smaller than Earth’s moon having a diameter of 3.100 km / 1.900 mi. It is primarily made of silicate rock and has a water-ice crust, and a probably iron-nickel core.

Its atmosphere is thin, composed primarily of oxygen. The surface is very smooth. In fact it is the smoothest of any known solid object in the Solar System. The apparent youth of the smoothness of the surface led to the hypothesis that a water ocean exists beneath it, which could conceivably harbor extraterrestrial life.

Currently, Europa probably has the highest of either having or developing life, and thus it is one of the most closely studied objects in the solar system.

Callisto is the second-largest moon of Jupiter and the third-largest moon in the Solar System after Ganymede and Saturn’s moon Titan. It has a diameter of about 4.821 km / 2.995 mi, having about 99% the diameter of the planet Mercury but only a third of its mass.

Named after a nymph of Greek mythology, also another one of Zeus’s lovers, Callisto is the farthest Galilean moon orbiting Saturn at a distance of 1.8 million km. It is not in a orbital resonance like the other three Galilean moons and thus it is not appreciably tidally heated like the others. It is tidally locked with Jupiter and it is less affected by Jupiter’s magnetosphere than the other inner satellites because of its remote orbit.

It is composed primarily out of equal amounts of rock and ices, with a density of about 1.83 g/cm 3 , the lowest of Jupiter’s satellites. Investigations by the Galileo spacecraft suggest that Callisto has a silicate core and possibly a subsurface ocean of liquid water at depths of 100 km.

Interestingly, the surface of Callisto is the oldest and most heavily cratered in the Solar System. It has an extremely thin atmosphere composed of carbon dioxide and probably molecular oxygen.

The presence of an ocean within Callisto opens the possibility that it could harbor life but conditions are thought to be less favorable than on Europa. Regardless, it is considered the most suitable planet for a human base for future exploration of the Jovian system due to low radiation levels.

Irregular Moons

The irregular moons are small and have elliptical and inclined orbits. They are thought to be captured asteroids or fragments of captured asteroids. Their exact number is unknown but they are further divided into sub-divisions – groups, in which they share similar orbital elements and thus may have a common origin.

There are 4 groups:

• The Himalia group – a clustered group of moons with orbits around 11 million to 12 million km / 6 to 7 million mi from Jupiter.
• The Ananke group – a group with a retrograde orbit with rather indistinct borders, averaging from 21 million km / 13 million mi from Jupiter with an average inclination of 149 degrees.
• The Carme group – they are a group with a fairly distinct retrograde orbit that averages from 23 million km / 14 million mi from Jupiter with an average inclination of 165 degrees.
• The Pasiphae group – a very dispersed and only vaguely distinct retrograde group that covers all the outermost moons.
• There are three irregular moons that stand out from these groups:
• Themisto – it orbits halfway between the Galilean moons and the Himalia group.
• Carpo – it is at the inner edge of the Ananke group and orbits Jupiter in prograde direction.
• Valetudo – this moon has a prograde orbit but overlaps the retrograde groups and may result in future collisions with those groups.

Planetary Rings

Jupiter has a faint planetary ring system composed of three main segments: an inner torus of particles known as the halo, a relatively bright main ring, and an outer gossamer ring.

They appear to be made out of dust rather than ice as with Saturn’s rings. It is believed that the main ring is made of material ejected from the satellites Adrastea and Metis.

In a similar manor, the moons Thebe and Amalthea probably produce the two distinct components of the dusty gossamer ring.

Life Habitability

Since it doesn’t have a true surface but rather swirling fluids it is not conducive to life as we know it. Ganymede, Callisto, and Europa on the other hand, have higher chances of sustaining life.

Future plans for Jupiter

Juno is a spacecraft that was launched in 2011 and even now it is still analyzing Jupiter and sending data. Future missions are already set in motion for Ganymede, Europa, Callisto and Io. They are set to be launched on 2020 and 2026. The high probability of life, the powerful volcanic activity and the overall missing details of Jupiter are strong factors in driving these missions.

Did you know?

• When Jupiter was formed it had twice its current diameter.
• Jupiter shrinks 2 cm every year because it radiates too much heath.
• Jupiter is so massive that its barycenter with the Sun lies above the Sun's surface at 1.068 solar radii from the Sun's center. It is the only planet whose barycenter with the Sun lies outside the volume of the Sun.
• If Jupiter would be 75 times more massive, it would probably become a star.
• If a person who weighs 100 pounds on Earth would somehow stand on the surface of Jupiter, that person would weigh about 240 pounds due to Jupiter’s gravitational force.
• Although Simon Marius, a German astronomer, is not credited with the sole discovery of the Galilean satellites, his names for the moons were adopted.
• Jupiter experiences almost 200 times more asteroid and comet impacts than Earth
• Jupiter has been called the Solar System's vacuum cleaner, because of its immense gravity well. It receives the most frequent comet impacts of the Solar System's planets.
• It was thought that the planet served to partially shield the inner system from cometary bombardment. However, recent computer simulations suggest that Jupiter does not cause a net decrease in the number of comets that pass through the inner Solar System, as its gravity perturbs their orbits inward roughly as often as it accretes or ejects them. This topic remains controversial.
• Jupiter may have been responsible for the Late Heavy Bombardment of the inner Solar System's history.

Image source:

• https://upload.wikimedia.org/wikipedia/commons/5/50/Jupiter%2C_image_taken_by_NASA%27s_Hubble_Space_Telescope%2C_June_2019_-_Edited.jpg
• https://upload.wikimedia.org/wikipedia/commons/c/cb/Jupiter-bonatti.png
• https://upload.wikimedia.org/wikipedia/commons/0/02/SolarSystem_OrdersOfMagnitude_Sun-Jupiter-Earth-Moon.jpg
• https://www.inverse.com/article/56489-jupiter-at-opposition-2019
• https://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Jupiter_diagram.svg/800px-Jupiter_diagram.svg.png
• https://upload.wikimedia.org/wikipedia/commons/8/84/PIA21973-AboveTheCloudsOfJupiter-JunoSpacecraft-20171216.jpg
• https://upload.wikimedia.org/wikipedia/commons/0/04/Hubble_Captures_Vivid_Auroras_in_Jupiter%27s_Atmosphere.jpg
• https://upload.wikimedia.org/wikipedia/commons/3/30/NASA14135-Jupiter-GreatRedSpot-Shrinks-20140515.jpg
• https://upload.wikimedia.org/wikipedia/commons/f/f2/Ganymede_g1_true-edit1.jpg
• https://upload.wikimedia.org/wikipedia/commons/7/7b/Io_highest_resolution_true_color.jpg
• https://upload.wikimedia.org/wikipedia/commons/e/e4/Europa-moon-with-margins.jpg
• https://upload.wikimedia.org/wikipedia/commons/e/e9/Callisto.jpg
• https://upload.wikimedia.org/wikipedia/commons/2/29/PIA01627_Ringe.jpg

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Jupiter's "Grand Tack" Reshaped the Solar System

Jupiter, long settled in its position as the fifth planet from our sun, was a rolling stone in its youth. Over the eons, the giant planet roamed toward the center of the solar system and back out again, at one point moving in about as close as Mars is now. The planet’s travels profoundly influenced the solar system, changing the nature of the asteroid belt and making Mars smaller than it should have been. These details are based on a new model of the early solar system developed by NAI scientists at the Virtual Planetary Laboratory, the Goddard Center for Astrobiology, and their colleagues. Their paper appears in a recent issue of Nature.

“We refer to Jupiter’s path as the Grand Tack, because the big theme in this work is Jupiter migrating toward the sun and then stopping, turning around, and migrating back outward,” says the paper’s first author, Kevin Walsh of the Southwest Research Institute in Boulder, Colo. “This change in direction is like the course that a sailboat takes when it tacks around a buoy.”

According to the new model, Jupiter formed in a region of space about three-and-a-half times as far from the sun as Earth is (3.5 astronomical units). Because a huge amount of gas still swirled around the sun back then, the giant planet got caught in the currents of flowing gas and started to get pulled toward the sun. Jupiter spiraled slowly inward until it settled at a distance of about 1.5 astronomical units—about where Mars is now. (Mars was not there yet.)

“We theorize that Jupiter stopped migrating toward the sun because of Saturn,” says Avi Mandell, a planetary scientist at NASA Goddard and a co-author on the paper. The other co-authors are Alessandro Morbidelli at the Observatoire de la Cote d’Azur in Nice, France; Sean Raymond at the Observatoire de Bordeaux in France; and David O’Brien at the Planetary Science Institute in Tucson, Ariz.

Like Jupiter, Saturn got drawn toward the sun shortly after it formed, and the model holds that once the two massive planets came close enough to each other, their fates became permanently linked. Gradually, all the gas in between the two planets got expelled, bringing their sun-bound death spiral to a halt and eventually reversing the direction of their motion. The two planets journeyed outward together until Jupiter reached its current position at 5.2 astronomical units and Saturn came to rest at about 7 astronomical units. (Later, other forces pushed Saturn out to 9.5 astronomical units, where it is today.)

The effects of these movements, which took hundreds of thousands to millions of years, were extraordinary.

Jupiter’s Do-Si-Do

“Jupiter migrating in and then all the way back out again can solve the long-standing mystery of why the asteroid belt is made up of both dry, rocky objects and icy objects,” Mandell says.

Astronomers think that the asteroid belt exists because Jupiter’s gravity prevented the rocky material there from coming together to form a planet; instead, the zone remained a loose collection of objects. Some scientists previously considered the possibility that Jupiter could have moved close to the sun at some point, but this presented a major problem: Jupiter was expected to scatter the material in the asteroid belt so much that the belt would no longer exist.

“For a long time, that idea limited what we imagined Jupiter could have done,” Walsh notes.

Rather than having Jupiter destroy the asteroid belt as it moved toward the sun, the Grand Tack model has Jupiter perturbing the objects and pushing the whole zone farther out. “Jupiter’s migration process was slow,” explains Mandell, “so when it neared the asteroid belt, it was not a violent collision but more of a do-si-do, with Jupiter deflecting the objects and essentially switching places with the asteroid belt.”

In the same way, as Jupiter moved away from the sun, the planet nudged the asteroid belt back inward and into its familiar location between the modern orbits of Mars and Jupiter. And because Jupiter traveled much farther out than it had been before, it reached the region of space where icy objects are found. The massive planet deflected some of these icy objects toward the sun and into the asteroid belt.

“The end result is that the asteroid belt has rocky objects from the inner solar system and icy objects from the outer solar system,” says Walsh. “Our model puts the right material in the right places, for what we see in the asteroid belt today.”

Poor Little Mars

The time that Jupiter spent in the inner solar system had another major effect: its presence made Mars smaller than it otherwise would have been. “Why Mars is so small has been the unsolvable problem in the formation of our solar system,” says Mandell. “It was the team’s initial motivation for developing a new model of the formation of the solar system.”

Because Mars formed farther out than Venus and Earth, it had more raw materials to draw on and should be larger than Venus and Earth. Instead, it’s smaller. “For planetary scientists, this never made sense,” Mandell adds.

But if, as the Grand Tack model suggests, Jupiter spent some time parked in the inner solar system, it would have scattered some material available for making planets. Much of the material past about 1 astronomical unit would have been dispersed, leaving poor Mars out at 1.5 astronomical units with slim pickings. Earth and Venus, however, would have formed in the region richest in planet-making material.

“With the Grand Tack model, we actually set out to explain the formation of a small Mars, and in doing so, we had to account for the asteroid belt,” says Walsh. “To our surprise, the model’s explanation of the asteroid belt became one of the nicest results and helps us understand that region better than we did before.”

Another bonus is that the new model puts Jupiter, Saturn, and the other giant planets in positions that fit very well with the “Nice model,” a relatively new theory that explains the movements of these large planets later in the solar system’s history.

The Grand Tack also makes our solar system very much like the other planetary systems that have been found so far. In many of those cases, enormous gas-giant planets called “hot Jupiters” sit extremely close to their host stars, much closer than Mercury is to the sun. For planetary scientists, this newfound likeness is comforting.

“Knowing that our own planets moved around a lot in the past makes our solar system much more like our neighbors than we previously thought,” says Walsh. “We’re not an outlier anymore.”

Elizabeth Zubritsky NASA Goddard Space Flight Center

Hubble Finds a Planet Forming in an Unconventional Way

NASA's Hubble Space Telescope has directly photographed evidence of a Jupiter-like protoplanet forming through what researchers describe as an "intense and violent process." This discovery supports a long-debated theory for how planets like Jupiter form, called "disk instability."

Interpreting this system is extremely challenging. This is one of the reasons why we needed Hubble for this project – a clean image to better separate the light from the disk and any planet.

Thayne Currie

Lead Researcher on the Study

The new world under construction is embedded in a protoplanetary disk of dust and gas with distinct spiral structure swirling around surrounding a young star that’s estimated to be around 2 million years old. That's about the age of our solar system when planet formation was underway. (The solar system's age is currently 4.6 billion years.)

"Nature is clever; it can produce planets in a range of different ways," said Thayne Currie of the Subaru Telescope and Eureka Scientific, lead researcher on the study.

All planets are made from material that originated in a circumstellar disk. The dominant theory for jovian planet formation is called "core accretion," a bottom-up approach where planets embedded in the disk grow from small objects – with sizes ranging from dust grains to boulders – colliding and sticking together as they orbit a star. This core then slowly accumulates gas from the disk. In contrast, the disk instability approach is a top-down model where as a massive disk around a star cools, gravity causes the disk to rapidly break up into one or more planet-mass fragments.

The newly forming planet, called AB Aurigae b, is probably about nine times more massive than Jupiter and orbits its host star at a whopping distance of 8.6 billion miles – over two times farther than Pluto is from our Sun. At that distance it would take a very long time, if ever, for a Jupiter-sized planet to form by core accretion. This leads researchers to conclude that the disk instability has enabled this planet to form at such a great distance. And, it is in a striking contrast to expectations of planet formation by the widely accepted core accretion model.

The new analysis combines data from two Hubble instruments: the Space Telescope Imaging Spectrograph and the Near Infrared Camera and Multi-Object Spectrograph. These data were compared to those from a state-of-the-art planet imaging instrument called SCExAO on Japan's 8.2-meter Subaru Telescope located at the summit of Mauna Kea, Hawaii. The wealth of data from space and ground-based telescopes proved critical, because distinguishing between infant planets and complex disk features unrelated to planets is very difficult.

"Interpreting this system is extremely challenging," Currie said. "This is one of the reasons why we needed Hubble for this project – a clean image to better separate the light from the disk and any planet."

Nature itself also provided a helping hand: the vast disk of dust and gas swirling around the star AB Aurigae is tilted nearly face-on to our view from Earth.

Currie emphasized that Hubble's longevity played a particular role in helping researchers measure the protoplanet's orbit. He was originally very skeptical that AB Aurigae b was a planet. The archival data from Hubble, combined with imaging from Subaru, proved to be a turning point in changing his mind.

"We could not detect this motion on the order of a year or two years," Currie said. "Hubble provided a time baseline, combined with Subaru data, of 13 years, which was sufficient to be able to detect orbital motion."

"This result leverages ground and space observations and we get to go back in time with Hubble archival observations," Olivier Guyon of the University of Arizona, Tucson, and Subaru Telescope, Hawaii added. "AB Aurigae b has now been looked at in multiple wavelengths, and a consistent picture has emerged – one that's very solid."

The team's results are published in the April 4 issue of Nature Astronomy .

"This new discovery is strong evidence that some gas giant planets can form by the disk instability mechanism," Alan Boss of the Carnegie Institution of Science in Washington, D.C. emphasized. "In the end, gravity is all that counts, as the leftovers of the star-formation process will end up being pulled together by gravity to form planets, one way or the other."

Understanding the early days of the formation of Jupiter-like planets provides astronomers with more context into the history of our own solar system. This discovery paves the way for future studies of the chemical make-up of protoplanetary disks like AB Aurigae, including with NASA's James Webb Space Telescope.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

Media Contacts:

Claire Andreoli NASA's  Goddard Space Flight Center 301-286-1940

Hannah Braun Space Telescope Science Institute, Baltimore, Maryland

Ray Villard Space Telescope Science Institute, Baltimore, Maryland

Science Contacts:

Thayne Currie Subaru Telescope, Hilo, Hawaii Eureka Scientific Inc., Oakland, California

Olivier Guyon Subaru Telescope, Hilo, Hawaii University of Arizona, Tucson, Arizona

Kellen Lawson University of Oklahoma, Norman, Oklahoma

Related Terms

• Astrophysics
• Goddard Space Flight Center
• Hubble Space Telescope

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2. the last letter of the answer is: k, 3. there are 2 vowels in the hidden word:.

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