Astronomers have just announced they have found the first intact planet orbiting a white dwarf*, the dead core of a star that was once much like the Sun.
There are lots of cool things about this discovery, but one of the weirdest is that the planet is bigger than the star!
But then, it almost has to be. Here's how this works.
WD 1856+354 (let's just call it WD 1856) is a white dwarf about 80 light years away in the constellation of Draco. It may be part of a triple system, orbiting a pair of stars called G 229-20, although it's not clear if it actually orbits them or is coincidentally close to them in the sky.
It was observed by TESS, the Transiting Exoplanet Survey Satellite, which is scanning the whole sky looking for planets orbiting other stars. If we happen to see a planet's orbit edge-on, then once per orbit it'll pass directly in front of the star, dimming it a bit. TESS has already detected quite a few planets since it started work in 2018.
The transit seen by the Gran Telescopio Canarias (left) shows the white dwarf’s light dropping by over half, which was also ...