White dwarfs are cores of the stars, which were once very similar to the Sun. At some point, these stars simply used all of the lighter elements which fueled their existence and flared up into a bloated giant and then burned down into cores full of oxygen and carbon, which were much larger than the Earth. With their fusion ended, they radiated away from the remaining temperature, and our capability of detecting them was also fading out.
We know that stars have planets around them. But what happens to a planet that’s orbiting a star, which blows on its way to becoming a white dwarf? Some say that these stars have the material similar to a rocky planet right on their surface. But there’s a new example out there, with gas, which has been drawn off from a planet that looks like Neptune.
This white dwarf star presents sulfur on its surface
The white dwarf star called WD J091405.30+191412.25 was found to have hydrogen on its surface. This is quite normal. It would have burned most of its hydrogen during its past life, and many white dwarfs get the material from nearby stars. But here there was no case of a nearby star. Also, there was sulfur on the surface of the white dwarf. We don’t really see much sulfur on stars, which shows that the material did not have a stellar origin.
But the question is: how did it get there? They needed to take a look at the lines in the spectrum, which was produced by hydrogen, oxygen, and sulfur. All of these were split into two peaks. This was actually a sign of a rotating disk of material. On one side, the white dwarf rotates away from us, and it adds a red shift to the light. On the other hand, it rotates towards us, and it adds a blue shift to the light.