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.
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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.
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."

Cool! Scientists are really trying

Openbusiness2:
Cool! Scientists are really trying

so many discoveries everyday. A cool planet exploitation may follow.

22brains:
A cool planet exploitation may follow.

I doubt it. Because the world lacks unity of purpose.

Openbusiness2:
Cool! Scientists are really trying

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. That got me thinking about the phrase in the Bible "a thousand years is like a day in God's eyes."

22brains:
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. That got me thinking about the phrase in the Bible "a thousand years is like a day in God's eyes."

Time is relative to space and dimension. Have you ever had a looooooooong dream that felt like several hours, and you were going from one scene to another, one place to another etc but then you wake up, check the time and only 25 minutes has passed ? Proves that the measurements of time in the dimension inside the matrix vortex of the human mind is different from the one in the dimension of space we physically occupy. Then in contrast of the bolded, it gets even more interesting when you put it in the context of Genesis, where it is said God created the entire world (universe) in "6 days" and gets even more interesting when it says God rested on the '7th day" and then in actual reality of it, the "7th day" = eternity . I can only say that God is truly Great, actually The Greatest

Nice one. Let them locate another planet that can sustain live in every form. It's only a matter of searching well. E dey.

Nice discovry...oya USA Come and take the lead again.

Oil dey your head. Real oil.