Astronomy

How was Jupiter formed

How was Jupiter formed


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Two days ago I went to a mathematics conference where there was a paper presented on Jupiter's formation via the disk-instability model.

I know that there are two different theories for the formation of the planets. One of them is the Core accretion model and the other one is the disk-instability model. I also tried to read this paper on planetary formation in which they said 161 planets were put on to test. 90% followed Core accretion model and rest of them followed the later model. Did not say anything explicit about Jupiter.

Jupiter is too close to the Sun to follow the Disk-Instability model (I am not sure completely).

Now I want to know which model Jupiter follows for its formation.
(I asked this question on physics stack-exchange too but unfortunately there were no answers)


Maxwell's Smith Prize Essay on the formation of the Rings of Saturn is relevant. Using structural stability as his criterion, he deduced that the 'rings' could only consist of a single almost infinite mass of very small particulates each orbiting in accord with Newtonian dynamics--the correct result as verified by NASA/ Cassini. Applying the same approach to a forming solar system this analysis shows that rings of particulates are a structurally stable attractor for the dynamics, provided the central star is much larger than the mean particulate size. I am now well outside my comfort zone so will leave further inferences to others :). Maxwell's essay on rings of saturn


Exploring Jupiter’s Interior

Figure 1. Image Credits: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill https://www.nasa.gov/image-feature/jpl/dark-and-stormy-jupiter.

As the biggest planet in our solar system, Jupiter has sparked the curious minds of people for centuries. Among the many mysteries surrounding Jupiter, its interior remains one of the most fascinating secrets that we seek to understand. Although there is no certainty, it is widely accepted that Jupiter has a core and we will explore theories about its composition that support this theory. The spacecraft, Juno, is currently orbiting Jupiter to delve deep in discovering the planet’s evolution and atmosphere, sending back information that continues to amaze peoples minds. Jupiter’s core and composition will be assessed to determine what really lies in Jupiter’s interior and for the possibility of the core being composed of dense materials instead of solids.

About Jupiter

Figure 2. A true-color simulated image of Jupiter pieced together by four images taken by NASA’s Cassini spacecraft on December 7, 2000. Image credit: NASA/JPL/University of Arizona https://www.jpl.nasa.gov/spaceimages/details.php?id=pia02873

Named after the king of the Roman gods, Jupiter formed about 4.5 billion years ago. Jupiter is the biggest planet in our solar system, with a radius of 43,440.7 miles, and is the fifth planet from the Sun. The distance between Jupiter and the Sun is 484 million miles, or 5.2 astronomical units (AU), therefore taking sunlight 43 minutes to reach its surface. 1

Jupiter is predominantly composed of hydrogen and helium, making it a gas giant. Deep inside its atmosphere, pressure and temperatures increase, and compress the hydrogen into a liquid creating the largest ocean in the solar system. Jupiter likely has three distinct cloud layers that altogether span close to 44 miles (71 kilometers). The top layer is thought to be composed of ammonia ice, with the middle layer to be ammonium hydro-sulfide crystals, and the innermost layer to be water ice and vapor. With its fast rotation, it is believed that it drives electrical currents in this region and generates its magnetic field which influences the region of space called the Jovian magnetosphere. It reaches 600,000 to 2 million miles towards the Sun, and tapers almost 600 million miles behind Jupiter. This magnetic field rotates with the planet and collects any particles with an electric charge. 1

Figure 3. A visual representation of Jupiter’s large magnetosphere. Image credit: John Spencer http://www.boulder.swri.edu/

Planet and Solar System Formation

The history of how our solar system has formed remains a challenge to explain as we are unable to study the process itself. The current understanding of the theory for the formation of planets is related to that of stars and the overall creation of the solar system.

Figure 4. Artist’s conception of a protoplanetary disk. Image credit: NASA/JPL-Caltech/T. Pyle
https://exoplanets.nasa.gov/news/229/these-arent-the-planets-youre-looking-for/

The prevailing theory is that a star and its planets are formed out of a collapsing interstellar cloud of dust and gas within a larger cloud called a nebula. As the material in the cloud collapses, gravity pulls the materials closer together. The center of the cloud is compressed and rises in temperature, causing the material to churn and flatten into circumstellar or protoplanetary disks (Figure 4). 5

These flat rotating disks of dust and gas reaching up to tens to hundreds of AU, are the birthplace of planets. 6 The disk continues to spin around the star, and the material within begins to stick together and grow, attracting more material as the disk becomes larger. At this point, the baby planets, or planetesimals, begin to form. The interior is composed of mostly rocky materials, while the exterior is composed of gas and ice. This allowed for the formation of smaller, rocky planetesimals close to the star to form, such as Mercury, Venus, Earth and Mars. Jupiter, Saturn, Uranus and Neptune are giants of ice and gas and were formed further away. 5

Jupiter is believed to be the first planet to have formed in the solar system. The massive gas giant was supposedly formed one million years after the formation of the Sun. This was difficult to discover as we previously had no samples from anything beyond Jupiter’s asteroid belt. Thomas Kruijer, a researcher at Lawrence Livermore National Laboratory, stated that isotopes from meteorite samples had to be used and examined to determine Jupiter’s maximum age. 7

It was theorized that after Jupiter formed, it had migrated closer and then farther away from the Sun. This path that Jupiter took is called the Grand Tack. According to this model, Jupiter was likely formed around 3.5 AU from the Sun, however, but the wild currents of gas and dust particles caused the planet to roam as close as 1.5 AU, the orbit that Mars is currently in. 8 Saturn also followed this pattern before all of the dust particles between them were driven out and the two planets’ bound paths became inverted. 8 The end result of this migration placed Jupiter where it currently resides, at 5.2 AU from the Sun.

Figure 5. A Solar Sytem model. Image credits: CC 2.0 https://www.flickr.com/photos/[email protected]/2818891443

Figure 6. An artist’s interpretation of a a young sun-like star surrounded by a planet-forming disk of gas and dust. Image credit: NASA/JPL-Caltech
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA12008

With current understandings, a critical component of planetary formation is the necessity of a dense core for the accumulation of materials and elements. The key to understanding what composes Jupiter’s core lies within understanding how the planet itself was formed. The theories on how Jupiter was formed is directly related to what lies at its core. However, much like what Jupiter’s core is actually made of, the planet’s detailed formation is also a mystery. The most popular theory on how gas giants were formed is the core-nucleated accretion theory, which involves gas being gravitationally accreted onto a sufficiently massive core. 10 With the interior of the protoplanetary disk being exposed to more rocky conditions, which produced the terrestrial planets, and the exterior to ice and gas, it is probable that at the center of Jupiter lies a core composed of rock or ice. 5

Theories on Jupiter’s Core

The most accepted theory about Jupiter’s core is that it is dense and composed of heavy elements. The core grew from a nearby collection of debris, water ice, and pieces of comets and asteroids. These materials fused together becoming what is called Planetesimals, and these large chunks of matter collided with one another to form Jupiter’s core. When the core was large enough, helium and hydrogen were attracted and continued to accumulate until Jupiter was fully formed. 11

Data from the Galileo probe mass spectrometer that was dropped into Jupiter revealed that Jupiter is depleted in water and oxygen, but has carbon levels 1.7 times higher then the Sun. Using this information, it was questioned where all the water that had helped build Jupiter’s core was. It was proposed in 2004 that instead of water ice, Jupiter’s core was originally made of mainly tar, as tar is sticky and collects more rocks and is more durable compared to water ice. During the initial formation, the core grew large enough to accrete gas from the solar nebula these gases were hydrogen and helium. The accretion caused energy to heat up Jupiter and caused the tar to react and create methane, the third most abundant gas found in the solar system. 12

It was proposed in 2010 that Jupiter’s core composition has actually shrunk due to a collision with a protoplanetary and has a mixture of hydrogen, helium and heavy elements. With such a large body crashing into Jupiter’s core, there is a possibility that the collision could have lead to the core decaying and gases to rise up to Jupiter’s upper atmosphere layer. 13

Another theory is that Jupiter has no core at all. After the Sun’s birth, it is theorized that a large cloud of gas and dust surrounded the Sun, and in this cloud contained the initial materials to form Jupiter. As the temperature cooled down, the cloud condensed, which lead to small particles such as gas and dust to accumulate and caused density discrepancy among different regions. This accumulation enhanced gravitational power until it became large enough to form Jupiter. 11

Figure 7. A model of Jupiter’s interior, composed of a rocky core and a layer of liquid metallic hydrogen. Image credit: Kelvinsong CC BY-SA 3.0 https://en.wikipedia.org/wiki/Jupiter#/media/File:Jupiter_diagram.svg

Juno’s Mission to Jupiter

Juno’s principle goal is to understand Jupiter’s origin and evolution. Its mission objective is to explore its atmosphere in order to measure composition, temperature, cloud motions and discover what percentage of Jupiter’s atmosphere is water, which would give further evidence towards which planet formation theory is correct. Juno will also map Jupiter’s magnetic and gravitational fields, study its interior to determine if there is a core, as well as its magnetosphere near the north and south poles. 18

Figure 8. The Juno spacecraft and its science instruments. Image credit: NASA/JPL https://www.nasa.gov/mission_pages/juno/spacecraft/index.html

Juno was launched August 5th, 2011, from Cape Canaveral, Florida. 19 But the spacecraft circuited our solar system for five years for regular check-ups and testing on its equipment before returning to Earth for a boost. 20 When two objects in space fly near each other, they each feel a gravitational pull, but the smaller object will feel a bigger tug. When Juno reached Earth, a technique called the gravity assist, Juno took a small amount of the planets’ momentum to orbit the Sun, and used it to reach Jupiter. This flyby was essential to the mission’s success as during the time of launch, there was not a rocket powerful enough to send a spacecraft directly to Jupiter. 21

Juno arrived in Jupiter’s orbit on July 4th, 2016. To enter Jupiter’s orbit, Juno needed to complete the Jupiter Orbit Insertion, where it fired its engines at exactly the right moment and direction for the right amount of time entirely on its own to safely enter into orbit. Juno relies on solar power, so it needs to stay exposed to sunlight in Jupiter’s orbit, an area which is called the polar orbit. This orbit will take Juno over Jupiter’s poles, in a north-south direction. It takes Juno 11 days to complete a revolution around Jupiter, so a route was designed for Juno to cover the entirety of Jupiter’s surface by the time the mission is complete. 22

On Juno’s 11th orbit around Jupiter, it was discovered that the rotating zones and belts seen in the atmosphere can reach up to

1,900 miles (3,000 kilometers). Hydrogen is then conductive enough to be dragged into near-uniform rotation by the immensely powerful magnetic field. This data also held information about Jupiter’s interior structure and its composition. Regions of

Figure 9. An artist’s concept of the lightning distribution in Jupiter’s northern hemisphere, using a JunoCam image. Image credit: NASA/JPL-Caltech/SwRI/JunoCam https://www.jpl.nasa.gov/news/news.php?feature=7151

surprising magnetic field intensity were discovered on Jupiter, with the northern hemisphere having more complex magnetic fields then the southern hemisphere. Around halfway from the equator and the north pole is an area of intense and positive magnetic field, but it is bordered by areas that are negative and less intense. The magnetic field is different in the southern hemisphere, as it is consistently negative with increasing intensity. 23

On Juno’s 12th orbit, its discoveries were sent back to NASA to reveal the origins of Jupiter’s mysterious lightning (Figure) and help to improve our understanding of Jupiter’s thermal composition. Using the Microwave Radiometer Instrument (MWR), Juno detected 377 lightning discharges from its first eight orbits. These discoveries showed that the lightning distribution was found at both poles, but most of the activity was at the north pole. Scientists believe that this is because heat is generated from the sunlight that heats up the equator and creates stability in the upper atmosphere as warm air is prevented from escaping. But the poles don’t have this stability, and this allows warm gases from the interior to rise, driving convection and thus creating lightning. Juno’s 13th science pass will be completed on July 16th, 2018. 24

Juno has yet to come to a general consensus of what Jupiter’s core is made of, though it is still one of the primary reasons of this mission. With Juno’s mission extended until 2021, hopefully the answer to what Jupiter’s core is composed of will be discovered. 25

Conclusion

As Jupiter was the first planet formed in our solar system, the planet could contain many answers to the mysteries of what our solar system and its planets are composed of. With many elements pertaining to Jupiter that remain unknown, there are ongoing efforts to seek explanations. When seeking to understand what Jupiter’s core could be composed of, it is important to look at how a gas giant is formed. Information such as where Jupiter may have originally been formed, its atmospheric and central composition, elements such as metallic hydrogen and Jupiter’s magnetosphere and the multitude of possible theories can help contribute to Jupiter’s interior. With Juno’s ongoing mission to orbit Jupiter until 2021, we can potentially learn what Jupiter’s interior contains and finally have an answer for one of the greatest mysteries of our solar system.


How Palomar’s Big Eye Telescope Forever Changed Astronomy

200 inch Hale telescope at Palomar Observatory shown at night Built 1948 and named for George Ellery . [+] Hale (1868-1938) Courtesy of Mount Wilson and Palomar Observatories. (Photo by: Photo12/Universal Images Group via Getty Images)

Universal Images Group via Getty Images

For those unfamiliar with how George Ellery Hale’s 200-inch Big Eye Telescope at Palomar observatory forever changed astronomy, Linda Schweizer’s recent book will be a revelation.

Hale’s early 20 th- century designs for a mountaintop observatory in Southern California’s Peninsular Ranges had by 1948 morphed into one of the world’s greatest scientific instruments. And the observatory remains an astronomical workhorse even today.

“The casting of the Big Eye’s 200-inch-diameter Pyrex mirror, the construction of its massive dome and horseshoe mount, and its first images of the universe generated as much public excitement as would the Apollo moon missions and the Hubble Space Telescope decades later,” Schweizer writes in “Cosmic Odyssey: How Intrepid Astronomers at Palomar Observatory Changed Our View of the Universe.”

Constructed with funds provided by The Rockefeller Foundation and dedicated as the 200-inch Hale Telescope on June 3, 1948, she notes that its big eye “encountered quasars and supermassive black holes, understood the chemistry that turns stardust into life.” And it was all due to the foresight of Hale, one very ambitious young astrophysicist from Chicago.

By the time he designed Palomar, Hale had already “masterminded the design and construction of four consecutive world’s largest telescopes, all dedicated between 1897 and 1948,” writes Schweizer. But the Palomar project took three times longer to complete than initially envisaged and suffering from complete mental exhaustion, in 1936 Hale became too ill to lead the project. He died two years later, a full decade before the Hale telescope’s dedication.

In twelve succinct chapters, Schweizer offers a very readable and understandable summary of our astronomical progress over the last 75 years as primarily seen through the lens of this one optical observatory. It’s not an easy task to offer up such an historical survey to the general public, but Schweizer does it with aplomb.

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As Schweizer notes, the observatory’s 48-inch Schmidt telescope spent its first seven years photographing 900 square fields surveying “hundreds of millions of never-before seen objects showed up, such as individual and clustered stars and galaxies, nebulae, comets, and asteroids,” mapping three-quarters of the entire sky. This type of survey technique paved the way for the hale telescope to hone-in on these objects and make some of the 20 th century’s most significant discoveries.

It’s obvious that Schweizer has a Ph.D. in astronomy because she seems completely at ease in describing the theories she documents in this compelling volume.

Here are a few of Palomar’s most significant breakthroughs.

—- The cosmos is expanding away from us in all directions.

Astronomer Edwin Hubble usually gets credit for confirmation that our cosmos is in fact expanding. He proved that there’s a direct relationship between the recessional speeds of distant galaxies and their distances from Earth.

But in the late 1950s, Allan Sandage —- one of Hubble’s proteges, used observations with the Palomar Hale Telescope to note that the universe is expanding away from us in isotropic fashion, or equally in all directions, which set the stage for contemporary cosmology.

—- Confirmation of stellar nucleosynthesis (the generation of elements via nuclear processes).

Elements such as carbon, nitrogen, oxygen, silicon, up to and including iron are created during the brief lives of massive stars, the author notes which she writes is crucial to enrichment of the interstellar medium and the formation of second and third generation stars like our own Sun. By the late 1950s, observations at Palomar were revolutionizing our understanding of how heavy elements are formed. In a 1957 Reviews of Modern Physics paper, “Synthesis of the Elements in Stars,” the authors proposed a sweeping theory of nucleosynthesis within dense, hot stellar interiors.

—- The discovery that our Milky Way galaxy formed from a collapsing proto-galactic cloud of dust and gas.

Sandage, along with astronomers Olin Eggen and Donald Lynden-Bell, used data taken from observations at Palomar in their classic paper that first described how an ancient gas cloud collapsed into our current Milky Way Galaxy. The authors described how a cloud some ten times the diameter of our current galaxy collapsed some 10 billion years ago, or 3.7 billion years after the Big Bang to form in a monolithic collapse. The 1962 paper, published in The Astrophysical Journal, opened the door to decades of galactic models describing similar processes throughout the cosmos.

—- A new method of looking for supernovae.

Swiss American astronomer Fritz Zwicky spent thousands of nights obtaining deep sky images with the observatory’s 18-inch Schmidt camera, the first functioning telescope at Palomar.

His work was looking for supernovae which at the time were very poorly understood, however, Schweizer writes that he concentrated on finding exploding stars outside our own galaxy by focusing on clusters of galaxies, instead of just one individual galaxy.

Zwicky superposed the current night’s photographic exposures on the previous night’s image of the same part of the sky. Schweizer notes that surveys using such methodology was completely novel at the time. But the author writes that it “inaugurated a tradition of periodically surveying sky for supernovae with Schmidt cameras which continues to this day.”

The hardcover edition of “Cosmic Odyssey” offers explanatory sidebars and high-quality vintage black and white and color historical photos of the observatory’s astronomers as well as the observatory’s telescopes. And the author also does a fine job in referencing external analysis and observations that augmented Palomar’s initial observations.

However, there are a couple of caveats. Don’t expect a narrative style in the vein of creative non-fiction. The book is filled with factual, workman-like prose and by its very nature covers so much material in such a condensed form that readers used to more leisurely in-depth narratives may find it frustrating.

Yet as an up-to-date reference for this historic observatory’s many contributions, “Cosmic Odyssey” is invaluable.


Jupiter is wetter than we thought, which helps explain how it formed

Jupiter contains more water than previously thought, according to data from NASA’s Juno spacecraft, which could help us understand how the planet formed in the first place.

We have been confused about Jupiter’s water for some time. In 1996, NASA’s Galileo probe found that the planet’s water levels, and thus oxygen levels, were a lot lower than expected, contradicting theories about how the solar system formed.

We think that the solar system was created when a gigantic ball of gas collapsed, forming the &hellip

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Juno Will Answer An Important Question About How Jupiter Formed

How did astronomers conclude that Jupiter was the first planet formed in our solar system? originally appeared on Quora: the knowledge sharing network where compelling questions are answered by people with unique insights.

Answer by Robert Frost, Instructor and Flight Controller at NASA, on Quora:

How Jupiter formed is still somewhat a mystery. We are hoping that Juno’s observations will help refine the models by telling us more about what is at the center or core of Jupiter.

The standard models of planetary formation have revolved (pardon the pun) around accretion. However, observations of other solar systems have raised some questions about whether accretion could be solely responsible.

A gas giant, such as Jupiter, has to suck up a lot of gas from the protoplanetary disk. The models tell us that rocky planets tend to form in the inner part of a solar system and gas giants tend to form in the outer part of a star system because the solar wind gradually blows most of the gas outwards, so by the time the inner planet cores have accreted enough mass to gravitationally capture gas, the gas has moved outwards.

This is where the problem comes in. That all seemed reasonable until observations of other systems revealed that the protoplanetary disk has a short lifetime. In order for Jupiter to get so big, it would have had to form very quickly - to capture the gas before it was gone.

That has introduced new models called disk instability formation. This alternative method would have allowed Jupiter to form faster than accretion would have formed the other planets. So, if true, technically we could say Jupiter formed first. But these models are still quite speculative. If Juno reveals that Jupiter has a large rocky core, then Jupiter should have formed concurrently with the other planets. If it reveals an absence of a large rocky core, then more credence is given to there being alternate processes such as disk instability.

Core accretion models indicate it would take between 500,000 - 10,000,000 years to form Jupiter. Disk instability models say it could be done in 100–1000 years.

This question originally appeared on Quora. Ask a question, get a great answer. Learn from experts and access insider knowledge. You can follow Quora on Twitter, Facebook, and Google+. More questions:


Jupiter may be to thank for life on Earth

As astronomers have gained the ability gaze at far-off exoplanets, they have started to realize our solar system is more unique than they could have imagined.

According to Gregory Laughlin, professor and chair of astronomy and astrophysics at UC Santa Cruz, "Our solar system is looking increasingly like an oddball."

For one thing, most systems have bigger planets orbiting closer to their central stars. In our solar system, some of our smallest planets (Earth included) are nearer the sun, while giants like Saturn and Jupiter are further out.

Laughlin and California Institute of Technology's Konstantin Batygin have come up with a theory for this apparent aberration. In a paper published in the Proceedings of the National Academy of Sciences Monday, they conclude that Jupiter is to blame - and to thank.

The two scientists use fresh calculations and simulations to propose that the early universe was actually populated by a number of super-Earths - planets larger than Earth but smaller than Neptune - but thanks to the gravitational influence of Jupiter acting on those planets, they were broken up and hurled into the sun billions of years ago.

Their model builds on something called the Grand Tack scenario, which was first posed in 2001 by a group at Queen Mary University of London and subsequently revisited in 2011 by a team at the Nice Observatory. In the early years of the solar system, the scenario proposed, when planetary bodies were still embedded in a disk of gas and dust around a young sun, the sun pulled the disk's gas in toward itself, drawing Jupiter in, too, as though on a giant conveyor belt. Because of Jupiter's massive size and gravitational influence, it snowplowed all the smaller planets in front of it into the sun, where they were demolished, only to be replaced later by the planets we know and love - and live on - today.

Batygin said about 10 percent of the material pushed along by Jupiter survived and eventually became the mass that formed Mercury, Venus, Earth and Mars tens of million years after the birth of the sun. By that time, much of the hydrogen and helium in the disk would have been long gone, partially explaining why Earth doesn't have a hydrogen atmosphere and thus is so hospitable.

If Earth would have formed around the time of this first-generation of planets, Batygin said it would have likely been much more gaseous and maybe ended up being much more inhospitable to life, along the lines of Venus.

"But Jupiter wiped the slate clean and destroyed the first generation of planetary bodies," Batygin told CBS News. "It sort of set the stage for the formation of a second generation of planets, which would have formed after the gases were gone. We are able to take advantage of exceptionally thin and favorable atmosphere, where you can see for miles and miles. That is a rare thing galactically speaking."

"All of this fits beautifully with other recent developments in understanding how the solar system evolved, while filling in some gaps."

Anders Johansen, a senior lecturer at the Lund Observatory in Sweden who did not take part in the study, said the findings illustrated that the solar system could have looked much different than today, but doesn't go so far as to prove the theory.

"I find that the study is interesting because it highlights that the solar system could have harbored one or several super-Earths that migrated into the sun following Jupiter's inwards migration," he said by email. "However, the authors do not show that this actually did happen in our solar system."

One lingering question remains: Why didn't Jupiter follow the same path as those other planets?

Batygin said Jupiter survived thanks in part to its close proximity to Saturn. Once the two massive planets got close enough, they locked into a special kind of relationship called an orbital resonance that saved Jupiter from destruction.

"Jupiter would have continued on that belt, eventually being dumped onto the sun, if not for its buddy, Saturn," Batygin said, adding that both planets were eventually sent outwards in the solar system.


It has been proposed that gas giants orbiting red giants at distances similar to that of Jupiter could be hot Jupiters due to the intense irradiation they would receive from their stars. It is very likely that in the Solar System Jupiter will become a hot Jupiter after the transformation of the Sun into a red giant. The recent discovery of particularly low density gas giants orbiting red giant stars supports this theory.

Hot Jupiters orbiting red giants would differ from those orbiting main-sequence stars in a number of ways, most notably the possibility of accreting material from the stellar winds of their stars and, assuming a fast rotation (not tidally locked to their stars), a much more evenly distributed heat with many narrow-banded jets. Their detection using the transit method would be much more difficult due to their tiny size compared to the stars they orbit, as well as the long time needed (months or even years) for one to transit their star as well as to be occulted by it.


Jupiter assembling: planet 96 light years away hints at how gas giants form

Astronomers have taken a photograph of a young planet beyond the solar system that may reveal clues as to how planets such as Jupiter are formed and influence their planetary siblings, a study released on Thursday shows.

Scientists used the newly commissioned Gemini Planet Imager, which is mounted on top of a telescope in Chile, to find the planet, known as 51 Eridani b. It circles a very young sun-like star that is located about 96 light years from Earth.

The planet – about double the size of Jupiter, Earth’s largest companion in our solar system – is positioned a bit farther away from its parent star than Saturn orbits the sun. 51 Eridani b is one of the smallest planets beyond the solar system to be directly imaged.

Image of 51 Eri b taken with the Gemini Planet Imager in December 2014. Photograph: J Rameau and C Marois /Gemini Observatory

Still radiating heat from its formation less than 20m years ago, or about 40m years after dinosaurs became extinct, 51 Eridani b is glowing in infrared light, which is how the telescope saw it.

“51 Eri b provides an opportunity to study in detail a planet that is still influenced by its formation initial conditions,” Stanford University astronomer Bruce Macintosh and colleagues wrote in this week’s issue of the journal Science.

Follow-up analysis revealed that the planet’s atmosphere, like Jupiter’s, is dominated by methane. The discovery provides an important clue for scientists trying to figure out how gas-giant planets form and evolve.

Simulated fly-by of the 51 Eridani star and planet system. Link to video

“51 Eri b is the first young planet that probably looks like Jupiter did billions of years ago, making it currently our most important cornerpiece of the planet-formation jigsaw puzzle,” University of Arizona planetary scientist Travis Barman said in a statement.

Astronomers have only been able to directly see a handful of planets beyond the solar system and nearly all of those have been five to 13 times as massive as Jupiter.

Other telescopes, like Nasa’s Kepler observatory, look for planets indirectly. Kepler, for example, looked for slight dips in the amount of light coming from target stars, a possible clue that an orbiting planet was crossing the face of its parent star.

Another method is to look for wobbles in starlight that may be caused by the slight gravitational tugs of circling planets.