Astronomers are happy as children. They can admire the core of the planet the size of Neptune

Astronomers from the University of Warwick have found in orbit around a distant star the gas giant’s nucleus devoid of all gas envelope. This is a unique opportunity to look inside such a planet.

The planet’s core, whose dimensions are comparable to those of Neptune, is most likely a gas giant, from which all its gas atmosphere has been stripped or is simply a failed gas giant, which failed to evolve at the beginning of its life.

Researchers from the Faculty of Physics at the University of Warwick described their discovery a few days ago in the journal Nature . There are many indications that the object they observed is the first exposed planetary nucleus. As such, it provides a unique opportunity to look into the deep interior of a gas giant.

The unusual object has been cataloged under the name TOI 849 b

TOI 849 b orbits around a sun-like star 730 light-years away. It is close enough to its star that it orbits it in just 18 hours, and the temperature on its surface reaches 1800K.

The planetary core was discovered as part of a sky survey performed with the TESS space telescope. Scientists were amazed to find that the object is located in the so-called Neptune Desert, i.e. in the area around the star in which there are never planets with a mass greater than the mass of Neptune.

After the discovery, astronomers explored the planet using the HARPS instrument installed at the La Silla Observatory in Chile. With its help, based on Doppler shifts, the mass of the planet was measured. The researchers found that the mass of the object is 2-3 times greater than the weight of Neptune, and the object itself is extremely dense – after all, 3 masses of Neptune are compressed into an object the size of one Neptune.

Although it is an unusually massive planet, it is far from the most massive planet we know. Nevertheless, it is the most massive planet of this size. As if it were small, it is extremely dense for an object the size of Neptune, which tells us that it has a very unusual history behind it. Its orbit also tells us a lot – we usually don’t discover planets with this mass in such a narrow orbit

– says Dr. David Armstrong from the Faculty of Physics at the University of Warwick.

What is TOI 849 b really?

TOI 849 b is the most massive rocky planet – with a density comparable to Earth – as we know it. We would expect that such a massive planet will attract large amounts of hydrogen and helium to itself during formation, which would eventually become Jupiter. The fact that there are no gases around it tells us that it is the exposed core of the planet. This is the first time we’ve discovered something like this.

This is the first time that an intact exposed giant gas core has been discovered in orbit around another star.

There are two theories explaining why we are observing the planet’s core rather than a typical gas giant.

The first theory says that it was once a planet similar to Jupiter, but that it lost almost all its gaseous envelope due to tidal interactions with its star or in collision with another planet. Intensive photo-evaporation of the atmosphere could also have had its share here, although it is not able to account for all lost gas.

The second theory is that he may be a failed gas giant. After the gas giant’s nucleus formed, something went wrong and it was never able to collect the right atmosphere from the surroundings. This could be the case if there was a break in the dust disk surrounding the planet, or if the planet was formed at a later stage of evolution, and in the environment there was not enough gas and dust from which the atmosphere could form.

Either way, either TOI 849 b was a gas giant, or is a failed gas giant. Both options tell us a lot. We now have a unique opportunity to look inside the gas giant – something we cannot do in the solar system. Meanwhile, scientists still have many questions about the interior of Jupiter, to which there was no way to answer.

Although we don’t have any information about its chemical composition yet, we will try to determine it using other telescopes. Because TOI 849 b is so close to its star, any existing atmosphere around this planet must be supplemented with matter from the planet’s core. Therefore, if we can detect any atmosphere, we will be able to determine the chemical composition of the very core of the former planet

– sums up Dr Armstrong.

Astronomers are happy as children. They can admire the core of the planet the size of Neptune

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