Scientists have identified a new kind of star that up until this point had only been considered hypothetically: an ancient sun that has lived so long, its outermost layer is now composed almost entirely of pure oxygen.
When relatively small stars – those with less than 10 times the mass of our Sun – get close to the end of their lifespan, they shed their outer layers and become what are called white dwarfs. Under high gravity, the heaviest elements descend into the star's dense core, while lighter elements such as hydrogen and helium rise to the surface.
At least, that's what usually happens. This star, dubbed SDSS J124043.01+671034.68, bucks the trend, with astronomers discovering its outer atmosphere is essentially greater than 99.99 percent oxygen. Only traces of other elements have been detected, including neon, magnesium, and silicon, but as for the hydrogen and helium you'd expect to find dominating the surface, there's no sign.
It's a puzzle for the team that found it, led by Souza Oliveira Kepler from the Federal University of Rio Grande do Sul in Brazil. "What happened to all these light elements?" he told William Herkewitz at Popular Mechanics. "How did they all get stripped away?"
Source: sciencealert.com