It seems almost weekly that scientists make new discoveries about space. This time it's the turn of a mysterious star that's been named after the two-faced Roman god, Janus.
The ingredients in stars are usually pretty evenly mixed throughout, but astronomers have discovered a bizarre star with two distinct faces, each made of a different element, which defies explanation.
White dwarf stars are the burnt-out husks that remain after stars like our Sun throw off their outer layers and leave just a compact core behind. Their atmospheres are usually dominated by either hydrogen or helium. But now, astronomers have spotted a white dwarf that doesn’t fit this description – and exactly how it came to be is a bit of a head-scratcher.
One half of this white dwarf is composed almost entirely of hydrogen, while the other is helium - the first time such a clear split has been seen for this kind of celestial object. No wonder it’s been nicknamed Janus, after the two-faced Roman god.
“The surface of the white dwarf completely changes from one side to the other,” said Ilaria Caiazzo, lead author of the study. “When I show the observations to people, they are blown away.”
The researchers have a few ideas about how this weird star became distinctly two-faced. Some white dwarfs are thought to transition between being hydrogen-dominated and helium-dominated over their lifetime, and Janus may be the first one caught in the act. Be that as it may, nobody is quite sure why it would change one face at a time.
However, the team think that the reason is probably due to the object’s strong magnetic field. If it’s stronger on one side than the other, it would prevent the hydrogen and helium from mixing properly - resulting in two faces.