First Giant Exoplanet Found Orbiting Extinguished Star

Katie Ramirez
September 20, 2020

"In a white dwarf system there's also a habitable zone, but because the white dwarf is really tiny and it's cooling off and is really, really faint, you have to huddle a lot closer to that star in order for it to be potentially habitable", Vanderburg told Salon.

The finding indicates it is possible for Jupiter-sized planets to survive their star's demise and settle into close orbits around what remains, researchers say. "First the star will swell up and get really, really big". However, that detection was based on light being emitted by a disk of debris and gas surrounding the star, which the researchers suggest must have been stripped from a Neptune-like planet. This finding should now inspire astronomers to search for similar objects around other white dwarfs. What's more, it is so close to the white dwarf that it completes an orbit 60 times faster than Mercury, which takes about 90 days to orbit the sun.

Siyi Xu, an assistant astronomer at the global Gemini Observatory in Hilo, Hawai, said: "We've known for a long time that after white dwarfs are born, distant small objects such as asteroids and comets can scatter inward towards these stars".

This makes it unlikely that any close planets could remain to orbit the star in its white dwarf phase, according to the study in Nature. Spitzer was created to make infrared observations and see objects that would be otherwise invisible in visible light. But if it's just a planet, planets are generally colder than stars and so there should be a little or no infrared light. "In this case the planet is bigger than its host star by a factor of 7!"

"What our Spitzer data showed is there's basically no infrared light at all", Mr Crossfield said. "That really put the final nail in the coffin that this thing is nearly certainly a planet, rather than a star". To overcome this impediment, the astronomers supplemented the TESS knowledge from higher-resolution ground-based telescopes, together with three run by novice astronomers. Thanks to data from the now-offline Spitzer Telescope, the team is confident this planet is about 14 times more massive than Jupiter, which is already a very large planet in the grand scheme. In the process of dying, some stars will drastically expand, becoming a huge "red giant", like Betelgeuse, and engulfing any of the planets orbiting close by.

"The discovery was somewhat surprising", said Andrew Vanderberg, an assistant professor at the University of Wisconsin-Madison who led the research published in Nature.

The researchers ran new simulations that provided a potential answer to the mystery. That process takes time - billions of years.

When our own sun becomes a red giant, is it possible that Earth could survive this stellar evolution?

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This is the white dwarf, an extremely dense stellar ember glowing faintly with leftover thermal energy and slowly fading over billions of years.

"Can planets actually survive that - or is that impossible?" While in graduate college, he was reviewing knowledge from TESS's predecessor, the Kepler house telescope, and observed a white dwarf with a cloud of particles round it. It's doable {that a} planet shut sufficient to such a dying star would discover itself within the liveable zone, the area close to a star the place liquid water can exist, presumed to be required for all times to come up and survive.

"The discovery came as something of a surprise", Vanderburg says.

It suggests that dead solar systems could actually host hospitable regions, Mr Vanderburg said.

Previous research suggested that some white dwarfs could hold distant remnants of their planetary systems.

Part of the reason that the discovery is so unusual is that it defies so much of what we know about planet formation, as researchers involved in the study explained to Salon.

That hot core, Vanderburg clarified, is the thing that we call a white dwarf - and one of the characterizing qualities of a white smaller person is that, due to its strong power of gravity, it will in general draw heavenly bodies toward it and split them up all the while.

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