Science & Military2020-07-02
Scientists have discovered the surviving core of a gas giant orbiting a distant star, offering the first ever glimpse of the interior of these mysterious planets.
The core is about the same size as Neptune, or around four times larger than Earth, although it isn't clear what happened to the planet's gaseous atmosphere.
According to researchers from the University of Warwick's department of physics, the atmosphere could have been stripped away or it may have failed to form early on in the planet's life.
Image: The planet could have once been similar to Jupiter. Pic: NASA
The planet core was found in a survey of stars by NASA's Transiting Exoplanet Survey Satellite (TESS) and offers a unique opportunity to learn about the composition of gas giants.
Planets such as Jupiter, Saturn and Neptune are believed to have a rocky core deep beneath the bulk of their mass which is made up of gases.
Although the new core, named TOI 849 b, is around the same size as Neptune, it is believed to have three times the mass, with the material making it being squashed much more densely.
Dr David Armstrong, lead author on the paper, said: "While this is an unusually massive planet, it's a long way from the most massive we know.
"But it is the most massive we know for its size, and extremely dense for something the size of Neptune, which tells us this planet has a very unusual history," he added.
"TOI 849 b is the most massive terrestrial planet - [a planet] that has an earth-like density - discovered.
"We would expect a planet this massive to have accreted large quantities of hydrogen and helium when it formed, growing into something similar to Jupiter. The fact that we don't see those gases lets us know this is an exposed planetary core."
Image: It was discovered by the Transiting Exoplanet Survey Satellite (TESS). Pic: NASA
Dr Armstrong said this was the first time scientists have discovered an intact exposed core of a gas giant orbiting around a star.
There are two theories as to why the planet's core has been exposed.
The first is that it was once similar to Jupiter but lost its outer gas, potentially through tidal disruption - when it was ripped apart from orbiting too close to its star - or in a collision with another planet.
Alternatively, it might be a failed gas giant, which never formed an atmosphere - for instance, if there was a gap in the disc of dust the planet formed from, or if the disc ran out of material.
Dr Armstrong added: "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.
"Although we don't have any information on its chemical composition yet, we can follow it up with other telescopes.
"Because TOI 849 b is so close to the star, any remaining atmosphere around the planet has to be constantly replenished from the core. So if we can measure that atmosphere then we can get an insight into the composition of the core itself."
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