𝔢𝔵𝔦𝔰𝔱𝔢𝔫𝔱𝔦𝔞𝔩

Merged White Dwarfs

When stars similar to our Sun end their lives, and Helium fusion comes to an end, gravity crushes the remaining oxygen and carbon down to form a white dwarf.

Most stars exist in binary formation with other similar stars, so it's not too unfamiliar to find a star system with binary white dwarfs, once main sequence binary partners, now even in their death, continuing to orbit one another.

If white dwarfs are close enough, over billions of years, they may eventually come together, merging and most likely going supernova. This happens because the mass of the two white dwarfs exceeds the Chandrasekhar limit of around 1.4 times the mass of the Sun, forcing the oxygen and carbon atoms to begin fusion again in a sudden burst, and leaving behind a neutron star, even a black hole if the mass is sufficient.

So it was a surprise when Scientists found two white dwarfs in a state of merger, super hot and stable.

PG 1654+322 and PG 1528+025 are two merging stars that appear to still be fusing helium and rather than the carbon and oxygen building up on the inside as the white dwarf forms, the carbon and oxygen has made its way into the atmosphere, something you'd not expect to see until the white dwarf has stabilized after helium fusion ends.

This makes it a very rare merger event, and evidence that in space, even when you think you've seen it all, you never have !