And sometimes, armed with those powerful telescopes, we find things we knew should exist and, it turns out, do exist. Case in point: take the star system HD265435. We can see a hot, tiny subdwarf star, and when we examine it closely, we can see that star moving and changing in brightness in the exact manner you’d expect if a much more tiny white dwarf star were nearby pulling on the subdwarf’s surface. 

In a new paper in Nature Astronomy led by Ingred Pelisoli, researchers describe how the subdwarf star’s brightness appears to vary over time ever so slightly and in exactly the way you’d expect if the star was teardrop-shaped instead of round. When that teardrop is edge on to us, we see more of the star and receive more light. When we are instead looking at the rounded top of the tear, we see a smaller area and less light. This distorted star is having its mass gravitationally stolen by the white dwarf, and over time, this is going to allow the white dwarf to grow until one day, roughly seventy million years in the future, the white dwarf has consumed so much matter that it explodes as a Type 1a supernova. 

While I don’t think any of us want to wait around to see that future explosion, it’s still exciting to get to watch the early stages of this mass transfer.

More Information

University of Warwick press release

W.M. Keck Observatory press release

“A hot subdwarf–white dwarf super-Chandrasekhar candidate supernova Ia progenitor,” Ingrid Pelisoli et al., 2021 July 12, Nature Astronomy