For the first time ever, scientists have discovered a giant planet still intact while orbiting a white dwarf. This is a very important discovery as it proves that the death of a star doesn’t automatically mean that the planets orbiting it will get destroyed.
WD 1856 is one of three stars in a system located approximately 80 light-years away from us. The gigantic exoplanet candidate that’s still intact is called WD 1856 b and it completes a full orbit around its star every 34 hours. The huge Jupiter-size planet is about seven times bigger than the white dwarf.
In a statement, Andrew Vanderburg, who is an assistant professor of astronomy at the University of Wisconsin-Madison and the lead author of the study, said, “WD 1856 b somehow got very close to its white dwarf and managed to stay in one piece,” adding, “The white dwarf creation process destroys nearby planets, and anything that later gets too close is usually torn apart by the star's immense gravity.” “We still have many questions about how WD 1856 b arrived at its current location without meeting one of those fates.”
The scientists found the planet with NASA’s Transiting Exoplanet Survey Satellite (TESS) and then observed it in infrared light from the Spitzer Space Telescope. They couldn’t find any infrared glow from WD 1856 b which indicated that it was in fact a planet instead of just a star or brown dwarf. It is currently still considered a candidate until more observations can confirm it as being an exoplanet.
The fact that the planet is still intact is absolutely mind-blowing based on the transformation of WD 1856 going from a star to a red giant to a white dwarf. When sun-like stars have no more hydrogen fuel left, they turn into red giants that destroy anything near it. They eventually become white dwarfs which hold approximately the same mass as our sun but at a size a little larger than Earth. For comparison, when our own sun becomes a red giant in approximately 5 billion years, it would destroy Mercury, Venus, and possibly Earth.
With that being said, the planet WD 1856 b wouldn’t have been born where it is currently orbiting the white dwarf or else it would have been completely destroyed when the sun-like star turned into a red giant. The scientists have estimated that the planet was formed approximately 50 times further than where it is currently positioned.
How the planet got pushed so close to the white dwarf remains unknown. It may have been pushed in by the other two stars in the system or perhaps it got nudged in by coming into contact with a “rogue star”. However, “the most likely case involves several other Jupiter-size bodies close to WD 1856 b's original orbit,” explained Juliette Becker, who is a planetary scientist at the California Institute of Technology in Pasadena and a co-author of the study. She went on to say, “The gravitational influence of objects that big could easily allow for the instability you'd need to knock a planet inward.”
The team has a lot more work to do, like find out exactly what caused WD 1856 b to move in so close to the white dwarf, and to see if there are any other planets in that system. An illustration of what the planet would look like orbiting the white dwarf can be seen here.