Astronomers Discover Pair of Super-Rare ‘Two-Faced’ Stars [Video]

Scientists have discovered two rare white dwarfs—which are among the dimmest stars in the universe—that feature changes in their surface composition caused by magnetic fields. This brings the number of known “two-faced” white dwarfs to just seven.

White dwarfs are dense, core remnants of stars that have shed their outer layers and cool over billions of years as they steadily burn off their thermal energy.

The surface atmosphere of white dwarfs were originally thought to be composed mostly of hydrogen. However, in 2023, astronomers discovered an unusual white dwarf that had a surface made of hydrogen on one side and helium on the other.

Since then, a handful of other white dwarfs with differing surface compositions have been found, forming a growing class of “double-faced” white dwarfs.

“Given the several patchy-atmosphere objects known at this time, we are able to define the class of double-faced objects for the first time,” …