Astronomers discover two-faced white dwarf star with helium and hydrogen on two sides
Representational image of a dwarf star.
A two-faced star has been discovered by astronomers and its bizarre appearance has left them baffled. On one side, the white dwarf appears to have been composed mostly of hydrogen and helium appears to have filled the other side.
For the first time, a lone star has been discovered by astronomers that appears to have developed two contrasting faces spontaneously. “The surface of the white dwarf completely changes from one side to the other,” stated Dr Ilaria Caiazzo, who is an astrophysicist at Caltech who led the research. “When I show the observations to people, they are blown away," he added.
The dwarf star is more than 1,000 light-years away in the Cygnus constellation. It has been nicknamed Janus, inspired by the two-faced Roman god of transition. The star's formal scientific name is ZTF J203349.8+322901.1.
Initially, it was discovered using the Zwicky Transient Facility (ZTF), which is an instrument that scans the night skies from Caltech’s Palomar Observatory near San Diego.
Dwarf star spinning on its axis every 15 minutes
Caiazzo was looking for white dwarfs and they spotted one candidate because of its rapidly changing brightness. The observatory's further observations revealed that Janus has been rotating on its axis every 15 minutes.
Spectrometry measurements, which provide a star's chemical fingerprints, showed that hydrogen is entirely filled on one side of the object and the other side is filled entirely with helium.
If seen from close, the two sides of the star will appear bluish in colour and have a similar brightness, however, the helium side is likely to have a grainy, patchwork appearance similar to that of our sun, while the star's hydrogen side appears smooth.
It is difficult to explain the two-faced nature of the star as swirling gas makes up its exterior. “It’s hard for anything to be separated,” stated Caiazzo. The scientists feel that Janus can be undergoing a rare transition which has been predicted to occur because of white dwarf evolution.
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“Not all but some white dwarfs transition from being hydrogen- to helium-dominated on their surface. We might have possibly caught one such white dwarf in the act,” Caiazzo said. In that case, the scientists feel that the transition must be occurring in a lopsided way because of an asymmetric magnetic field.
“If the magnetic field is stronger on one side, it could be limiting convection (bubbling in the helium layer). “On the other side, convection could be winning out and so the hydrogen layer has been lost,” Caiazzo said.
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