Scientists find first ever planet with its insides exposed

Andrew Griffin
Wednesday 01 July 2020 15:26
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Scientists find the first planet with its insides exposed

Scientists have found the first planet with its core exposed.

The discovery represents the first time that researchers have been able to look into the inside of a planet, potentially offering an unprecedented understanding of how such worlds are formed.

The core is roughly the size of Neptune, and is thought to be a gas giant like our other neighbours Jupiter and Saturn. But it appears to have either been stripped of its gaseous atmosphere, or never failed to form one.

Instead, researchers can see the core that would normally be found inside such an exoplanet. That allows them to look inside the interior of the world and learn about its composition.

The newly discovered planet orbits a star similar to our Sun, and is found about 730 light years away. It is known as TOI 849 b, and conditions there are intense: it is so close to its star that a year takes 18 hours, and the surface temperature is around 1,500C.

That places the planet right in the Neptunian Desert, the region near stars where planets the size of Neptune are rarely found.

“The planet is strangely close to its star, considering its mass,” said David Armstrong from the University of Warwick, the lead author of the study, in a statement. “In other words, we don’t see planets with this mass at these short orbital periods.”

Researchers were able to conclude that it was just a planetary core by conducting detailed measurements, which found that the planet is about 40 times heavier than the Earth, but only 3.4 times as large. That density must mean that it is made up mostly of iron, rock and water, with only small amounts of hydrogen and helium.

“The fact that we don’t see those gases lets us know TOI 849 b is an exposed planetary core,” said Dr Armstrong.

TOI 849 b was first found by Nasa’s Transiting Exoplanet Survey Satellite, which hunts for planets by looking for the signature dip in brightness that happens when they move in front of their star. It was then further analysed by the HARPS instrument run by the European Southern Observatory, which uses the Doppler effect to measure exoplanets by looking for the wobble in their light that happens as they move nearer and further from us.

“One way or another, TOI 849 b either used to be a gas giant or is a ‘failed’ gas giant,” said Dr Armstrong.

“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.”

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