Wed. Aug 5th, 2020

Exposed planetary core offers a unique glimpse of innermost layers

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The surviving core of a planet has been found orbiting a distant star, offering astronomers a glimpse into its innermost layers.

Located around 730 light years away from Earth, the ‘exposed’ planetary core, known as TOI 849 b, is about the size of Neptune.

The scientists believe TOI 849 b may have been a gas giant similar to Jupiter but lost nearly all of its outer gas, possibly due to a collision with another planet, or through tidal disruption, where the planet was ripped apart because it was orbiting too close to its star.

Alternatively, they say, it could also be a ‘failed’ gas giant, where something went wrong and it did not form an atmosphere.

The researchers say that the findings, published in the journal Nature, offer an ‘unique opportunity’ to examine the interior of a planet and learn about its composition.

Dr David Armstrong, from the University of Warwick Department of Physics, who is lead author on the study, said: ‘This is the first time that we’ve discovered an intact exposed core of a gas giant around a star.’

He added: ‘One way or another, TOI 849 b either used to be a gas giant or is a ‘failed’ gas giant. 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.’

TOI 849 b was found by Nasa’s planet-hunting spacecraft TESS. By analysing the amount of light blocked by TOI 849 b as it passed in front of its host star, scientists were able to calculate its size and orbital period.

They found TOI 849 b circles very close to its host star, with an 18-hour orbital period. Calculations reveal its mass to be two-to-three times higher than Neptune.

Dr Armstrong said: ‘The planet is strangely close to its star, considering its mass. In other words, we don’t see planets with this mass at these short orbital periods.’

TOI 849 b is also believed to be extremely dense and may ‘primarily consist of iron, rock and water, but only very little hydrogen and helium’.

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