Astronomers just found a dead star evaporating a giant, icy planet - CNET

An artist's impression of the WDJ0914+1914 system, where a dead white dwarf star is stripping away the atmosphere of a gas giant planet four times its size.

ESO/M. Kornmesser

We think of stars as humongous objects that hold sway over everything in their considerable vicinity, but for the first time astronomers have spotted a giant planet that circles a dying dwarf star only a quarter of its size. 

The puny sun exerts its dwindling force over the planet, stripping away its atmosphere and spinning an elegant disc of gas around itself in the process. 

The oddball star carries the uninspired name WDJ0914+1914, located some 1,500 light years away, and the evaporating planet around it is thought to be something like Neptune based on the levels of hydrogen, oxygen and sulphur in the gassy disc. Yes, this planet is quite literally releasing silent but deadly stinky fumes across its solar system.

"Such a system has never been seen before, and it was immediately clear to me that this was a unique star," lead researcher Boris Gänsicke from the University of Warwick in the UK said in a release. "We knew that there had to be something exceptional going on in this system, and speculated that it may be related to some type of planetary remnant."   

An international team used observational data from multiple telescopes and theoretical models to conclude that while the white dwarf star is ancient, it's five times hotter than our sun. The nearby giant planet is icy by contrast and orbits very close in, making its way around the star in just 10 days. All along the way, energetic photons from the star are peeling off the planet's atmosphere and some of that gas is getting pulled into the swirling disc that initially made the star system jump out at astronomers. 

A study laying out the discovery was published Wednesday in the journal Nature. 

WDJ0914+1914 also provides an intriguing preview of the fate of our own solar system. The star was likely once a larger star like our sun, which will eventually run out of hydrogen fuel and puff up into a red giant that will consume our planet. Sometime after this cosmic carnage, the sun will shed its outer layers and leave behind a burnt-out white dwarf core like WDJ0914+1914. We could imagine that many eons down the road our sun will just be a dead white dwarf orbited by the giant outer planets Jupiter, Saturn, Uranus and Neptune.

But what's weird is the very close orbit of the giant planet around WDJ0914+1914. It's close enough that it should have been consumed during the star's red giant phase, implying that its orbit may have moved closer in at some point after the star's violent transition to dwarf size.

"Until recently, very few astronomers paused to ponder the fate of planets orbiting dying stars. This discovery of a planet orbiting closely around a burnt-out stellar core forcefully demonstrates that the Universe is time and again challenging our minds to step beyond our established ideas," concludes Gänsicke.

The good news here is that there may be a way to see our sun make it all the way to its white dwarf phase, so long as you're able to survive a few billion more years and able to relocate and survive on Jupiter or Saturn. 

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Originally published Dec. 4, 2:17 p.m. PT. 

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https://www.cnet.com/news/astronomers-just-found-a-dead-star-evaporating-a-giant-icy-planet/

2019-12-05 04:10:00Z
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