Astronomers discover never-before-seen two-faced star
Astronomers have made a first-of-its-kind discovery — a white dwarf star with two completely different faces.
White dwarfs are burnt remains of dead stars. Our sun will become a white dwarf in about 5 billion years after it swells into a red giant star, blows out its outer material and, with only the core left, shrinks back into a blinding white-hot remnant.
The newly discovered white dwarf has two sides, one made of hydrogen and the other made of helium. Researchers have nicknamed the star Janus, for the Roman god of transition, which has two faces. A study detailing the findings was published July 19 in the journal Nature.
“The surface of the white dwarf completely changes from one side to the other,” said lead study author Ilaria Caiazzo, a postdoctoral scholar research associate in astronomy at the California Institute of Technology, in a statement. “When I show the observations to people, they are blown away.”
White dwarfs are incredibly dense, compressing a mass comparable to our sun’s into something equivalent to an Earth-size planet.
The strong gravitational influence at play during the death of a star means that the remaining heavy elements move toward the center while lighter elements like hydrogen or helium rise to the upper layer. Given the blazing temperatures of white dwarfs, the hottest ones have hydrogen atmospheres. As the stars cool over time, they tend to have helium atmospheres.
But typical white dwarfs don’t have one side of the star devoted to one element, and the other dominated by another.
The unusual stellar remnant was first detected by the Zwicky Transient Facility, located at Caltech’s Palomar Observatory. Caiazzo used the instrument, which scans the skies each night, for a recent survey of highly magnetized white dwarfs when an object appeared that rapidly changed in brightness.
Astronomers have made a first-of-its-kind discovery — a white dwarf star with two completely different faces. White dwarfs are burnt remains of dead stars. Our sun will become a white dwarf in about 5 billion years after it swells into a red giant star, blows out its outer material and, with only the core left, shrinks back…