Jupiter-sized planet found orbiting distant white dwarf star

Astronomers have discovered a Jupiter-sized planet orbiting a distant white dwarf star, which is incredibly still intact. 

The planet, christened ‘WD 1856 b’ is located about 80 light years away in the northern constellation Draco.  

White dwarfs are the incredibly dense remains of sun-sized stars after they exhaust their nuclear fuel, shrunk down to roughly the size of Earth. 

WD 1856 b looms over its tiny star, which it circles every 34 hours thanks to an incredibly close orbit. 

The planet is roughly 20 times closer to the white dwarf than Mercury is to the Sun. 

Usually, as a star is dying, it engulfs its surrounding planets, meaning WD 1856 b is unique for somehow avoiding destruction. 

This discovery shows that it is possible for Jupiter-sized planets to survive their star’s demise and settle into close orbits around the remaining embers.

‘It’s a pleasant surprise,’ said lead researcher Andrew Vanderburg at the University of Wisconsin-Madison in the US.

‘We’ve never seen evidence before of a planet coming in so close to a white dwarf and surviving.’

Vanderburg led the international collaboration of astronomers who analysed the data gathered by multiple light-reading telescopes, including NASA’s space telescope TESS and two large ground-based telescopes in the Canary Islands. 

TESS monitors large swaths of the sky for nearly a month at a time. 

It captures changes in stellar brightness caused when a planet crosses in front of, or ‘transits’, its star. 

Researchers spotted a star whose brightness dimmed by half about every one-and-a-half days – a sign that something big was passing in front of it on a tight orbit. 

But it was hard to interpret the data because the glare from a nearby star was interfering with TESS’s measurements. 

To overcome this, the astronomers supplemented the TESS data from higher-resolution ground-based telescopes, including three run by amateur astronomers. 

‘Once the glare was under control, in one night, they got much nicer and much cleaner data than we got with a month of observations from space,’ said Vanderburg. 

White dwarfs are so much smaller than normal stars like our Sun – roughly the size of Earth. 

Therefore, large planets passing in front of them block a lot of the star’s light, making detection by ground-based telescopes much simpler.

The data revealed that a planet roughly the size of Jupiter, perhaps a little larger, was orbiting very close to its star. 

‘We can actually see WD 1856 b’s shadow passing in front of the star as it orbits, so we know that it’s there,’ Vanderburg said.

Vanderburg’s team believes the gas giant started off much farther from the star and moved into its current orbit after the star evolved into a white dwarf.  

The discovery raises questions about the fate of planets orbiting stars, which are destined to become white dwarfs. 

Our Sun, for example, is set to burn out and die in about 5 to 10 billion years. 

Of the thousands of planets outside the Solar System that astronomers have discovered, most orbit stars will eventually evolve into red giants and then into white dwarfs. 

During this process, any planets in close orbits will be engulfed by the star – but this is a fate that WD 1856b somehow managed to avoid.

‘Our discovery suggests that WD 1856b must have originally orbited far away from the star, and then somehow journeyed inwards after the star became a white dwarf,’ said Vanderburg. 

‘Now that we know that planets can survive the journey without being broken up by the white dwarf’s gravity, we can look for other, smaller planets.’ 

Last year, scientists at the University of Warwick claimed the first evidence of a giant planet orbiting a dead white dwarf star known as WDJ0914+1914.

Vanderburg said the new discovery is even more important because it’s the first intact planet orbiting a white dwarf – a crucial difference. 

‘The big difference between this and the previous discovery of WDJ0914+1914 is that there they did not actually detect the planet in its orbit – they instead detected debris from it in orbit and falling onto the surface of the star,’ Vanderburg said.

‘So while we knew that the planet came close to the white dwarf in that system, we don’t actually know that the planet survived the journey – in fact, we know that at the very least it is losing material since we see the debris.

Vanderburg and his team told MailOnline that they found no evidence for debris, indicating a intact planet.  

‘This shows us that planets actually can survive the journey close to the white dwarf, which is important because it implies that other smaller and rocky planets could come close, where they would be warm enough to have liquid water on their surfaces and potentially be habitable, long after the star died.’  

However, there ‘s just a slim chance that the Earth could survive the Sun’s red-giant phase in the distant future, the researchers believe.  

The study has been published in the journal Nature.