Astronomy

What might the surface of Jupiter's rocky core look like?

What might the surface of Jupiter's rocky core look like?


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Jupiter is posited, in some models, to have a rocky core about the size of a few Earths. If we could see through the thick gaseous atmosphere, what topographical features might we find on the rocky core? I know that no probe has ever sent data from Jupiter's (hypothesized) solid surface, and that orbiters probably can't penetrate the clouds to produce a topographic map, but do we at least have any educated guesses as to what sort of surface features are and are not likely to exist? For example, given Jupiter's massive gravity, would the surface be extremely smooth? Or would it not be out of the question to observe things like impact craters or mountain ranges?


An answer to your question is not known at this time. From the Internal Structure section of Jupiter's Wikipedia page,

Jupiter is thought to consist of a dense core with a mixture of elements, a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen. Beyond this basic outline, there is still considerable uncertainty. The core is often described as rocky, but its detailed composition is unknown, as are the properties of materials at the temperatures and pressures of those depths (see below). In 1997, the existence of the core was suggested by gravitational measurements, indicating a mass of from 12 to 45 times that of Earth, or roughly 4%-14% of the total mass of Jupiter.

(Emphasis mine)

The idea that the core is "rocky" or composed of metallic hydrogen is still unknown. Determining more about this is one of the objectives of the Juno mission currently in orbit. We may obtain better models of Jupiter's internal structure in the coming years, but at this point we just don't know.


There's not going to be any surface features.

First of all, let's assume you could look through a thick soup of metallic hydrogen. This material has densities starting at that of water, going to the densities of solid rock and even above, while still remaining liquid.
On a sidenote: No space probe will ever be able to look into that mess. Only gravitational measurments will help.

In recent years, it has been shown that under such conditions typical minerals are thermodynamically not stable, and thus will dissolve into the hydrogen-helium mix.
Thus, the core will not have any well-defined boundary, but it's going to look more like the following sketch (emphasis on sketch!):

which I took from this author's website, which has also a lot of follow-up in-depth research material linked.

In short: Essentially any topographical features can be ruled out. That thing down there will be a liquefied, high-pressure mess.

It is of course correct to say that Jupiter might not even have a core, but to build a planet with 1 Jupiter mass and one Jupiter radius one usually requires a certain amount of high-Z material in the core, which is why the core-idea is very attractive.
Also, going around on conferences this year, it seems that JUNO does find a 5-25 Earth masses core, but there is no publication on this yet.


What Would Happen To You If You Tried To Stand On Jupiter?

Let’s for a moment ignore the extreme conditions (gravity, atmospheric pressure, high temperature, and winds) that are found on the giant planet, and let’s just descend through the atmosphere. What we’d see is a spectacle like no other.

Far beneath Jupiter's atmosphere is a gigantic ocean of liquid metallic hydrogen, which would look and behave like mercury except that hydrogen has 60 percent the density of water. So, you would have to sink for tens of thousands of kilometers to reach a hot, molten, rocky core that's possibly solid.

The interior of Jupiter is not precisely mapped – that is one of the scientific goals of the Juno mission, which has just reached Jupiter. The probe will use precise gravitational and electromagnetic measurements to map what goes on underneath Jupiter’s clouds.

But it's been 20 years, so let's assume we can continue down. At 500 kilometers (310 miles), the visibility is almost completely gone and the thick ammonia clouds swirl all around us, with wind speeds of around 100 meters (330 feet) per second.

Underneath the ammonia clouds, there are more water clouds and more complex atmospheric effects that Juno will hopefully clarify. Current technology will have been pulverized by now, and our remains will now be traveling to a layer of supercritical fluid hydrogen – something not quite a gas but not exactly a liquid either.

After about 2.5 hours of exploration, we will have reached the liquid metallic hydrogen ocean. Heavy elements might reach the center after many more hours of falling. So, you couldn't exactly stand on this ocean. But below this, it's thought Jupiter may indeed have a rocky core, perhaps somewhat similar to terrestrial planets. Juno will help answer this question during its mission.

Jupiter has most of the planetary mass of the Solar System, and could easily fit all the other planets in its interior. There's a reason why it is the planetary king of the Solar System.


Reports: Astronomers capture impact on Jupiter's surface

A fireball thought to be an asteroid or comet hitting the surface of Jupiter was captured by two amateur astronomers early Monday, spaceweather.com reports.

One of the astronomers, identified as George Hall from Dallas, posted a screen shot in multiple reports and wrote about the discovery on his blog, George’s Astrophotography.

“The impact was observed by Dan Peterson visually this morning,” Hall wrote, crediting another space enthusiast with making the initial observation and posting what he saw online.

“When I saw the post, I went back and examined the videos that I had collected this morning …” he wrote in a post describing how he captured a video of the impact. “The video was captured with a 12" LX200GPS, 3x Televue Barlow, and Point Grey Flea 3 camera. The capture software was Astro IIDC.”

Hall posted a four-second video of the impact. He wrote that it was taken at about 6:35 a.m. Monday on his Flickr page.

Spaceweather.com compares Hall’s images with other impacts to Jupiter’s surface reported by NASA in 2009 and 2010.

A NASA Science News post from September 2010 stated: “Jupiter is getting hit surprisingly often by small asteroids, lighting up the giant planet's atmosphere with frequent fireballs.”

The post went on to say that Jupiter is frequently hit by small objects, causing impacts “bright enough to see through backyard telescopes on Earth.”

SpaceWeather.com wrote: “Astronomers around the world will now begin monitoring the impact site for signs of debris - either the cindery remains of the impactor or material dredged up from beneath Jupiter's cloud tops.”

Are you an amateur astronomer with images of the Jupiter impact? Share your videos with us or write about your observations in the comments below.


Exploring Jupiter

The first spacecraft to orbit the solar system's biggest planet was NASA 's Galileo in 1995 . The probe collected data about Jupiter for over seven years, which helped astronomers study several of its moons and better understand the planet's atmosphere. Galileo even observed a comet crashing into Jupiter's atmosphere in 1994 .

NASA 's Juno spacecraft was launched to Jupiter in 2011 and arrived in a polar orbit around the planet in 2016 . While passing over the planet's north and south poles, the mission has returned breathtaking images of Jupiter from a new point of view and allowed scientists to learn more about the massive planet's composition and gravitational and magnetic fields.

Both the European Space Agency and NASA are designing proposed missions that might visit Jupiter's moons in the next decade to find out if they hold liquid oceans—and maybe even life.


Do gas giants like Jupiter and Saturn have a "surface" somewhere down there?

The way I imagine it now is a moon sized super dense core surrounded by massive amounts of gas. I've always been confused about this.

Deep down enough, the pressure of the hydrogen becomes great enough that it turns metallic, which is a sort of degenerate matter—meaning there is no clear separation between individual hydrogen atoms and molecules, and all the electrons in the atoms have been compressed into the nuclei such that the entire system is just free nuclei and electrons.

It is also suspected that rocky cores roughly the size of Earth, but much more massive than it reside at the centre of Jupiter and Saturn, with the one in Saturn probably a little smaller.

However, there is no clear "surface" like what we are used to seeing on telluric/icy planets. The outer atmosphere consists of methane, ammonia, water ice and various other light gaseous clouds. Then about 100 km down from the cloud tops, it's mostly hydrogen. This hydrogen simply gets increasingly denser, until it becomes liquid several thousand kilometres down from the cloud tops. About a third to halfway to the centre of the planets, the pressure approaches 10 11 to 10 12 Pa, where the hydrogen becomes liquid metallic hydrogen. See here.

The metallic hydrogen behaves like a liquid metal. Because of the immense rotational velocities of Jupiter and Saturn, as well as their internal heat, this liquid metal behaves like a dynamo and generates very strong magnetic fields.

Furthermore, metallic hydrogen may have some intriguing properties, like being a room temperature superconductor (refer to the first link on metallic hydrogen).


2 Answers 2

You are correct: it would only look big because you know it's big.

There are really three things, purely in terms of your visual system which together tell you how big something is:

  • what angle it subtends in your vision
  • combined with focus & depth of field information
  • combined with comparing what your two eyes see, or how what you see changes if you move around.

For something like a planet the second and third of these don't give you any useful information: if you can see the planet as a whole then it's 'at infinity' from the point of view of the optical system of your eyes, and also you're not going to get any useful information from the differing input to your eyes, or by moving your head around.

So the things that tell you it's big are then just comparing it with other objects you know the size of. But, again, for a planet, there's not much useful to compare it with.


Massive Collision Cracked Young Jupiter’s Core

The gas giant’s interior reveals evidence of an ancient impact.

An artist’s illustration shows the moment of collision between young Jupiter and a smaller planet about 10 times the size of Earth. Credit: K. Suda & Y. Akimoto/Mabuchi Design Office, courtesy of Astrobiology Center, Japan

A Look at Other Worlds

Resurrecting Interest in a “Dead” Planet

In the chaotic early days of our solar system, catastrophic collisions were common. Jupiter’s fluid surface does not preserve telltale crater scars, nor is it tilted off its axis like some of its neighbors, but a new study published in Nature has uncovered deeper evidence of a massive impact in Jupiter’s past.

Jupiter is a gas giant famous for its sheer size⁠—over 300 times more massive than Earth⁠—and its swirling stormy surface. But until recently, little was known about the planet’s interior. The Juno space probe launched by NASA in 2011 entered Jupiter’s orbit in 2016 and continues to gather data on many aspects of the planet, including Jupiter’s chemical makeup and gravitational and magnetic fields.

The gravitational readings collected so far are “puzzling,” said Andrea Isella, an astronomer at Rice University in Houston and a coauthor on the new study. “We expected Jupiter to have a dense core, but the gravitational readings show that the core is diluted,” he says, meaning that heavier elements common in planetary cores are scattered throughout the hydrogen- and helium-rich envelope that encloses the planet.

Most planets, including Earth, have dense cores made up of heavy elements, like iron, that sink deep into the planet’s interior under the pull of gravity. Even gas giants like Jupiter are thought to initially form as dense, rocky or icy bodies that accumulate thick atmospheres composed of lighter elements, like hydrogen, over time.

Jupiter’s diluted core suggests that a head-on impact with a protoplanet may have stirred up the young planet’s core early in its history, Isella said. “Before the impact, it may have had a very dense core, surrounded by atmosphere. Then a head-on impact spread things out, diluting the core.” .

A major impact could have scattered the core of a young Jupiter about 4.5 billion years ago, producing the diluted core that persists today, as detected by NASA’s Juno spacecraft. Credit: Shang-Fei Liu/Sun Yat-sen University

To investigate the probabilities and potential outcomes of a large impactor colliding with Jupiter, lead author Shang-Fei Liu of Sun Yat-sen University in Guangzhou, China, and colleagues ran thousands of computer simulations of different types of impacts. The simulations showed at least a 40% chance that Jupiter would have collided with another planet within a few million years after its initial formation around 4.5 billion years ago, soon after the dawn of our solar system.

A New Theory

In 1994, the Shoemaker-Levy 9 comet collided with Jupiter, giving scientists a rare opportunity to observe two major objects in the solar system colliding.

“Bigger planets tend to gravitationally attract smaller bodies,” Isella said. “When a small asteroid or comet hits Jupiter, it’s like a fly impacting an 18-wheeler.”

Because of the strong gravitational focusing generated by the massive planet, passing objects are more likely to collide head-on with Jupiter than graze by, Isella said. The simulations showed that collision with a rocky planet about 10 times the size of Earth with a dense core rich in heavy elements could have created enough energy to scatter and dilute Jupiter’s core for billions of years.

A large-impact scenario for Jupiter has not been considered before, said Tristan Guillot, an astrophysicist at Côte d’Azur University in France who was not involved in the new study. “Jupiter does not show outward signs of impact, such as being tilted off its axis, such as we see with Saturn, Uranus, and Neptune.”

“This new study nicely explains the unexpected observations made by the Juno mission,” Guillot said.

More work will be needed to fit the impact theory into existing models of planetary formation, accounting for the distribution and accumulation of elements and heat in young planets, Guillot said. “This is very promising work that may lead us into a new paradigm for how the solar system might have formed: quite chaotically, with lots of giant impacts.”


At Jupiter’s Core

I first encountered the surface of Jupiter decades ago, in a study hall in John Burroughs School in St. Louis, Missouri. It was a warm spring day and I was theoretically trying to bone up for a math test two periods hence. But deciding to squeeze in a little reading before I hit the algebra, I read the paragraphs that follow and spent little of the next two hours thinking about anything else:

The wind came whipping out of eastern darkness, driving a lash of ammonia dust before it. In minutes, Edward Anglesey was blinded.

He clawed all four feet into the broken shards which were soil, hunched down and groped for his little smelter. The wind was an idiot bassoon in his skull. Something whipped across his back, drawing blood, a tree yanked up by the roots and spat a hundred miles. Lightning cracked, immensely far overhead where clouds boiled with night.

As if to reply, thunder toned in the ice mountains and a red gout of flame jumped and a hillside came booming down, spilling itself across the valley. The earth shivered.

Thus the opening of Poul Anderson’s “Call Me Joe,” published in Astounding Science Fiction in April of 1957, though I was reading it in a later anthology. “…a tree yanked up by the roots and spat a hundred miles…” — hard to keep your mind on studying after reading that! The cover illustration at left gives you an idea of the images this story creates as it follows the exploration of the Jovian surface by remote telepresence technologies. I couldn’t help recalling these images as I looked through new work on Jupiter’s core. Computer simulations studying what happens to hydrogen/helium mixtures at the extreme pressures and temperatures of Jupiter’s interior imply a rocky core of 14 to 18 Earth masses, a twentieth of the planet’s total mass.

I had more or less gotten used to the idea that there was no core in Jupiter at all, although some recent theories had suggested a smaller core of about seven Earth masses. Anderson’s bizarre life-forms, some native and some created by humans, move through a low-temperature world that eventually absorbs the story’s protagonist (you have to read this story if you haven’t already), but the reality of Jupiter may be far stranger, and certainly more complex than we fully understand. And it certainly seems to preclude wandering about on any kind of surface.

It now appears that the pressure and temperatures involved within the planet change hydrogen from a molecular to a metallic state, producing a material with high electrical conductivity that gives rise to the intense magnetic field. The core, in this latest view, would be made of metals, rocks and ices of methane, ammonia and water, with an Earth-like ball of iron and nickel at the very center. Burkhard Militzer (University of California, Berkeley) sums up the work this way:

“Our simulations show there is a big rocky object in the center surrounded by an ice layer and hardly any ice elsewhere in the planet. This is a very different result for the interior structure of Jupiter than other recent models, which predict a relatively small or hardly any core and a mixture of ices throughout the atmosphere… Basically, Jupiter’s interior resembles that of Saturn, with a Neptune or Uranus at the center.”

And that big rocky core gives an affirmative nod to the core accretion model of planetary formation, formed as it would have been by the collision of planetesimals from the primordial solar nebula. All of which is exciting stuff, but how much better to realize that the Juno mission to Jupiter, scheduled for a 2011 launch, should be able to return hard data to confirm or modify the new model. Juno will enter a highly elliptical polar orbit around the planet, studying the core question along with the planet’s magnetic field. Says Caltech’s Dave Stevenson:

“Juno’s extraordinarily accurate determination of the gravity and magnetic fields of Jupiter will enable us to understand what is going on deep down in the planet. These and other measurements will inform us about how Jupiter’s constituents are distributed, how Jupiter formed and how it evolved, which is a central part of our growing understanding of the nature of our solar system.”

Image: The Juno spacecraft in front of Jupiter. Juno is one of the largest planetary spacecraft to ever be launched. Credit: NASA.

Jupiter’s structure, then, can be critical in helping us understand how giant planets form, providing a way to look back at the early history of the Solar System. We’ll also learn about the relative abundance of water and oxygen, and gather data about the planet’s gravitational field and polar magnetosphere. Juno will use an Earth flyby for a gravity assist two years after launch, with arrival in Jupiter space in 2016. And rather than drawing on Radioisotope Thermal Generation (RTG) power, Juno will tap three solar panels to supply the needed juice despite its distance from the Sun. Efficient panels indeed.

The paper on Jupiter’s core is Militzer et al., “A Massive Core in Jupiter Predicted from First-Principles Simulations,” Astrophysical Journal Letters 688 (November 20, 2008), pp. L45–L48 (abstract, also available here).

Comments on this entry are closed.

So does this new model preclude Jupiter’s core being made of diamond?

Arthur C. Clarke would be very disappointed if so. However, most
diamond merchants might be happy, as having a world with a diamond
the size of Earth could do nasty things to their market, once we’re
able to reach the Jovian center – and we will when the Artilects start
disassembling the planets to make the Solarian Dyson Swarm. I bet
all that diamond could come in handy as construction material.

Regarding the Juno probe: Just wait until the folks who protested
Cassini in 1997 regarding its RTGs find out that NASA can send a
space probe all the way to Jupiter using only solar power, because
that was NASA’s big argument back then. that nuclear power was
needed to fuel a spacecraft beyond the Planetoid Belt.

Personally I have no issues with nuclear fuel for spacecraft and for
powering our society on Earth. In regards to deep space vessels
with RTGs and similar power sources, one might think the anti-nuke
forces would be glad to see the material permanently removed from
our planet to a vast place where the radiation is many, many times
worse than anything we can generate with our puny technologies.

And wait until they find out about the Orion nuclear bomb-powered
spaceship concept – though Carl Sagan once said that Orion was a
pretty good use for such devices and got them off the planet in the
process.

Regarding Jovian life forms, check out Ben Bova’s 2001 SF novel
titled Jupiter, about the possible creatures that could live in the
liquid portion of the giant planet. And Carl Sagan along with E. E.
Salpeter wrote a paper in 1976 about possible Jovians that live in
the more temperature layers of the planet’s atmosphere. This
was depicted in one of the early episodes of Cosmos in a very
memorable painting:

I think I answered Larry about diamond in a post to the HabitableZone that we both frequent – basically the pressure and temperature mean if there’s diamond it’s going to be liquid. But methane and ammonia both would be tiny compared to the complement of water down in Jupiter’s core, so it’s unlikely you’ll get diamond in any great quantities. Not enough carbon.

Poul Anderson’s story is set on the metallic hydrogen layer, assumed to be solid in his story. Of course now we know Jupiter is much too hot for it to be solid – instead it becomes liquid metallic hydrogen/helium, since the latest evidence is that the two alloy quite well. What form the water/ammonia/methane layer takes is anyone’s guess as all the pressure and temperature data falls short – though the article Paul references takes a good stab at the problem. The “ices” could well be solid, but only because of the pressure. Otherwise they’d explode into plasma. And such solids might be more fluid than what we normally imagine as “solid”, so it could be described as a sea, though I very much doubt anything could live in such a pyroabyssal environment, contra Bova’s novels.

And here are these guys, from the Time-Life Science Series book,
Planets, first published in 1966 and edited by Carl Sagan:

Forming Jupiter, Saturn, Uranus and Neptune in Few Million Years by Core Accretion

Authors: Omar G. Benvenuto, Andrea Fortier, Adrian Brunini

Abstract: Giant planet formation process is still not completely understood. The current most accepted paradigm, the core instability model, explains several observed properties of the solar system’s giant planets but, to date, has faced difficulties to account for a formation time shorter than the observational estimates of protoplanetary disks’ lifetimes, especially for the cases of Uranus and Neptune.

In the context of this model, and considering a recently proposed primordial solar system orbital structure, we performed numerical calculations of giant planet formation.

Our results show that if accreted planetesimals follow a size distribution in which most of the mass lies in 30-100 meter sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed according to the nucleated instability scenario.

The formation of each planet occurs within the time constraints and they end up with core masses in good agreement with present estimations.

Comments: 11 pages, 3 figures, in press (Icarus)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:0910.0468v1 [astro-ph.EP]

From: Andrea Fortier [view email]

[v1] Fri, 2 Oct 2009 20:01:39 GMT (28kb)

Did James Cameron Steal the Plot for ‘Avatar’?

While geeks the world over are eagerly awaiting Avatar, the return of James Cameron to the original sci-fi territory he’s proven a master over with The Abyss and Terminator/Terminator 2, fans of obscure science fiction novellas from 1957 are being struck with deja vu.

A reader tipped off genre champions io9 to the story Call Me Joe by Poul Anderson, a story that sounds remarkably like Cameron’s supposedly original script that revolves around humans that use the bodies of an alien species via a mental connection as physical avatars, and proceed to use said avatars to exploit the resources of the alien’s home world.

From the io9 post, “Like Avatar, Call Me Joe centers on a paraplegic – Ed Anglesey – who telepathically connects with an artificially created life form in order to explore a harsh planet (in this case, Jupiter). Anglesey, like Avatar’s Jake Sully, revels in the freedom and strength of his artificial created body, battles predators on the surface of Jupiter, and gradually goes native as he spends more time connected to his artificial body.”

Now that certainly sounds awfully similar to Avatar, and if that simple description is not evidence enough to inspire doubt, Avatar’s integrity is done no favors by the cover art for Call Me Joe. As seen at the top of this post, the life forms on the surface of Jupiter in Anderson’s story are large, blue-tinged hybrids between humanoids and cats which are not unlike the Na’vi, the humanoid-cat race that roams Cameron’s Pandora.


Difference Between Belt and Zone in Astronomy

Belts and zones are constituents of the atmosphere. In the giant planets, such as Jupiter and Saturn, the matter is not rocky or other solid matter. Most part of these planets are made up of gas or made up of gas compressed into a liquid form, mainly hydrogen and helium. Such planets are also called gas giants. These planets do not have a well-defined surface as their atmosphere plainly gets denser as we move towards the core. The core, however, might be metallic or rocky. During this transformation there might be liquid or liquid-like states in-between. In total, there are four gas giants in our solar system namely: Jupiter, Saturn, Uranus, and Neptune. All of these gas giants share many similar phenomena along with the formation of belts and zones. However, the formation of belts and zones is very prominent in the largest planet, Jupiter.

Due to counterclockwise circulating streams of material, bands are formed in the atmosphere. The darker bands are called belts, and the lighter bands are called zones. These belts and zones circulate on the planet moving parallel to the equator of the planet. These belts and zones cause the swirling effect of the atmosphere.

Belts are the darker bands in the atmosphere of Jupiter. They are at a lower altitude in the atmosphere. They are regions of low pressure and have an internal downdraft. The belts are similar to the low pressure cells in the atmosphere of our Earth, but they are not confined to a particular pocket. They are latitudinal bands encircling the entire planet. This might be due to the rapid rotation of the planet.

The belts are present in the downwards areas of the planet.

Zones are the lighter bands present in the atmosphere of the gas giants. They are present at higher altitudes and are regions of high pressure. An internal updraft exists in the zones. They resemble the high-pressure pockets present in the atmosphere of the Earth that play a crucial role in the phenomenon of climatic change. However, like the belts, the zones also encircle the whole planet.

Zones are present in the upward areas of the atmosphere of the planet.

The belts and zones differ in latitude and intensity during the year, but the general pattern remains the same. These are the result of convection currents in the atmosphere of the planet. The presence of the zones and belts imparts the characteristic colors to the planet due to the differences in the temperature of both bands.

The regions around the atmosphere of the equator rotate faster as compared to the planet as a whole. This speed decreases when moving towards the poles. That is why the band structure is lost towards the poles.


Core of a gas planet seen for the first time

It could be the core of a gas world like Jupiter, offering an unprecedented glimpse inside one of these giant planets.

Giant planets like Jupiter and Saturn have a solid planetary core beneath a thick envelope of hydrogen and helium gas.

But no-one has previously been able to see what these solid cores are like.

Now, a team of astronomers has discovered what they think are the rocky innards of a giant planet that's missing its thick atmosphere. Their findings have been published in the journal Nature.

Lead author David Armstrong, from Warwick University, and colleagues had been running a programme to detect exposed planetary cores in data from the Tess space telescope.

"This was one of the candidates we picked out as something to try to observe," he told BBC News.

"We followed it up with an instrument called the Harps spectrograph in Chile, which we used to measure the masses of these candidates. This one came out as being exceptionally massive - much more than we expected really. That's when we started to look into what could have caused that."

When the researchers first looked at the object, they thought it might be a binary star.

"We kept taking data and it turned out to still be a planet - just an exceptionally massive one for its size," Dr Armstrong explained.

Its radius is about three-and-a-half times larger than Earth's but the planet is around 39 times more massive. In this size range, the planet would be expected to have a significant component that's gas. Yet it has a density similar to Earth, appearing to be mostly rocky.

The object, called TOI 849 b, was found circling a star much like the Sun that's located 730 light-years away.

The core orbits so close to its parent star that a year is a mere 18 hours and its surface temperature is around 1,527C.

Researchers aren't sure whether the core lost its atmosphere in a collision or just never developed one.

If it was once similar to Jupiter, there are several ways it could have lost its gaseous envelope. These could include tidal disruption, where the planet is ripped apart from orbiting too close to its star, or even a collision with another planet late in its formation.

If it's a "failed" gas giant, this could have occurred if there was a gap in the disc of gas and dust that it emerged from, or if it formed late, after the disc ran out of material.

"I think one of the biggest clues is that we found the planet inside the 'Hot Neptunian desert', which is this region of parameter space where we don't typically find planets," Dr Armstrong told BBC News.

"That hints that it has gone through quite an unusual evolution. To me that hints that it is more likely that it did lose its atmosphere. but we'll need some more observations to be sure."

These further observations could help test ideas about how giant gas planets evolve.

"It's a first, telling us that planets like this exist and can be found. We have the opportunity to look at the core of a planet in a way that we can't do in our own Solar System.

"There are still big open questions about the nature of Jupiter's core, for example, so strange and unusual exoplanets like this give us a window into planet formation that we have no other way to explore."