Recently astronomers discovered a very unusual example of a white dwarf: one that seems to have one side composed of hydrogen and the other side of helium.
In billions of years’ time, once our sun has used up all its fuel and puffed up to become a red giant before throwing off layers to form a planetary nebula, all that will remain at its heart is a dense core called a white dwarf. This fate will be shared by the large majority of stars in our galaxy, so these burnt-out cores are common, with the mass of the sun squeezed into a space the size of the Earth. Recently, though, astronomers discovered a very unusual example of a white dwarf: one which seems to have one side composed of hydrogen and the other side of helium.
The two-faced white dwarf has been nicknamed Janus, after the Roman deity with two faces, and was investigated using data from the Zwicky Transient Facility at Caltech’s Palomar Observatory in San Diego, and the W.
