Astronomers at the University of Warwick recently discovered the surviving nucleus of a gas giant called TOI 849 b, which orbits a distant star. It is the first time that the exposed core of a planet has been observed.
The nucleus is believed to be a gas giant that was stripped of its gas atmosphere or was unable to form one in its early life.
The nucleus, the same size as Neptune in our solar system, has a mass 2-3 times greater than Neptune, but it is also incredibly dense, with all the material that makes up that mass crushed into an object of the same size.
TOI 849 b is located around a star, very similar to ours, approximately 730 light years away. It orbits so close to its host star that a year is only 18 hours, and its surface temperature is around 1800K.
Astronomers discovered TOI 849 b, located in the Neptunian Dessert, in a study of stars by NASA’s Transit Exoplanet Study Satellite (TESS) using a transit method. The Neptunian Dessert is a region close to the stars where we rarely see planets of the Neptune mass or larger.
The traffic signal was confirmed and refined using observations with ten telescopes from the Next Generation Transit Survey (NGTS) led by Warwick, based at the Paranal Observatory of the European Southern Observatory in Chile.
The object was then analyzed using the HARPS instrument, in a program run by the University of Warwick, at the La Silla Observatory of the European Southern Observatory in Chile. This uses the Doppler effect to measure the mass of exoplanets by measuring their ‘wobble’ – small movements toward and away from us that are recorded as small changes in the star’s light spectrum.
Lead author Dr. David Armstrong of the University of Warwick Physics Department said: “While this is an unusually massive planet, it is far from the most massive we know of. But it is the most massive we know of for its size, and extremely dense for something the size of Neptune, which tells us that this planet has a unique history. The fact that it’s in a strange place because of its mass also helps: we don’t see planets with this mass in these short orbital periods. “
“TOI 849 b is the most massive terrestrial planet, having a density similar to Earth, discovered. Hopefully such a massive planet would have accumulated large amounts of hydrogen and helium when it formed, turning into something similar to Jupiter. The fact that we do not see these gases lets us know that it is an exposed planetary nucleus.
“This is the first time we have discovered an intact exposed nucleus of a gas giant around a star.”
Dr. Armstrong adds: “In one way or another, TOI 849 b used to be either a gas giant or a ‘failed’ gas giant.
“It is the first time that it tells us that planets like this exist and can be found. We have the opportunity to see the nucleus of a planet in a way that we cannot do in our solar system. There are still big open questions about the nature of Jupiter’s core, for example, such strange and unusual exoplanets as this give us a window into planet formation that we have no other way to explore. “
“Although we still don’t have information about its chemical composition, we can follow it with other telescopes. Because TOI 849 b is so close to the star, any remaining atmosphere around the planet must constantly be replenished from the core. So if we can measure that atmosphere, then we can get an idea of the composition of the core itself. “
Magazine reference:
- A planetary core remaining in the hot Neptune desert ‘will be published in Nature, DOI: 10.1038 / s41586-020-2421-7
