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For the first time, a team of astronomers has observed the intact heart of a planet. This is the core survivor a gas giant that orbits a distant star to 730 light years away. Probably, he was exposed to be stripped of its atmosphere in a gaseous or could not form a in their first years of life. The finding, released in the journal “Nature”, offers an unprecedented view of the interior of a world extrasolar.

The kernel, called a TOI 849 b , is the same size as Neptune in our own solar system. It orbits so close to its host star -very similar to our Sun-that a year lasts only 18 hours and its surface temperature is hellish, of around 1500 ºC.

TOI 849 b was found by the satellite TESS of NASA, dedicated to search for new worlds in transit, that is to say, when you pass in front of its star host and to mitigate their brightness. It turned out a surprise, because it appeared in what astronomers call the “desert of Neptune”, a region close to the star where we rarely see planets the size of Neptune or larger.

Then, the object was analyzed using the instrument HARPS, in a program led by the University of Warwick, in the La Silla Observatory of the European Southern Observatory (ESO) in Chile. HARPS uses the Doppler effect to measure the mass of exoplanets by measuring their wobble: small movements that are recorded as small changes in the light spectrum of the star.

Massive to your size

The team determined that the mass of the object is two or three times greater than Neptune, but is also incredibly dense, with all the material that makes up the crushed mass in an object the same size as that world of our solar system.

“while this is a planet unusually massive, is very far from what the mass we know. But it’s more mass that we know of for its size, and extremely heavy for something the size of Neptune, which tells us that this planet has a story very unusual,” says David Armstrong, of the Department of Physics at Warwick and lead author of the study. “The fact that you’re in a strange place for your mass also helps: we don’t see planets with this mass at these short orbital periods,” he adds.

TOI 849 b is the terrestrial planet that has a similar density to the Earth, more mass discovered. “We would expect that a planet so massive would have accumulated large amounts of hydrogen and helium when it formed, becoming something similar to Jupiter. The fact that you do not see these gases allows us to know that this is a core planetary exposed”, explains the scientist. And stresses: “This is the first time that we discovered a core exposed intact of a gas giant around a star”.

Giant failed

But, what happened to this world? Why its rocky core was exposed? The researchers have two theories. The first is that it was once similar to Jupiter, but lost almost all of its external gas, for some reason, like orbiting too close to its star, or even after a collision with another planet. The fotoevaporación of the atmosphere to large-scale might also play a role, but cannot explain all of the gas that is lost.

The second theory suggests that a gas giant has “failed”. That is to say, that once formed the core of the gas giant, something might have gone wrong and never formed an atmosphere. This could have occurred if there had been a gap in the disk of dust that formed the planet, or if they formed later, and the album ran out of material. “In one way or another, TOI 849 b was a gas giant or it’s a gas giant ‘failed’,” concludes Armstrong.

“even Though we still do not have information on its chemical composition, we can follow it with other telescopes. Because TOI 849 b is so close to the star, any atmosphere remaining around the planet must be replenished constantly from the nucleus,” says the researcher. If you could measure the atmosphere, they could get an idea of the composition of the nucleus itself.

TOI 849 b may have much to teach us, even about the formation of worlds closest to you, as Jupiter. As we are reminded by the author, “we have the opportunity to look at the core of a planet in a way that we cannot do in our own solar system. There are still major open questions”.