Two-Faced Star With Helium and Hydrogen Sides Baffles Astronomers

Astronomers have discovered a two-faced star and are baffled by its bizarre appearance. The Guardian reports: The white dwarf appears to have one side composed almost entirely of hydrogen and the other side made up of helium. It is the first time that astronomers have discovered a lone star that appears to have spontaneously developed two contrasting faces. The object, which is more than 1,000 light years away in the Cygnus constellation, has been nicknamed Janus, after the two-faced Roman god of transition, although its formal scientific name is ZTF J203349.8+322901.1. It was initially discovered by the Zwicky Transient Facility (ZTF), an instrument that scans the skies every night from Caltech's Palomar Observatory near San Diego. "The surface of the white dwarf completely changes from one side to the other," said Dr Ilaria Caiazzo, an astrophysicist at Caltech who led the work. "When I show the observations to people, they are blown away." Caiazzo was searching for white dwarfs and one candidate star stood out due to its rapid changes in brightness. Further observations revealed that Janus was rotating on its axis every 15 minutes. Spectrometry measurements, which give the chemical fingerprints of a star, showed that one side of the object contained almost entirely hydrogen and the other almost entirely helium. If seen up close, both sides of the star would be bluish in colour and have a similar brightness, but the helium side would have a grainy, patchwork appearance like that of our own sun, while the hydrogen side would appear smooth. The findings are published in the journal Nature.Read more of this story at Slashdot.
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