Jekyll and Hyde just went astronomical. For the first time ever, a team of scientists from around the world have discovered a two-faced star.
With a bright blue tint, the white dwarf star is made of hydrogen on one side and helium on the other. The hydrogen side appears brighter, while the darker, helium side bubbles and spits away behind it.
The team behind the discovery nicknamed the white dwarf ‘Janus’, after the two-faced god in Roman mythology who represented transitions and dualities.
“When I show the observations to people, they are blown away.” said Ilaria Caiazzo, a postdoctoral scholar at Caltech, USA, who led the study on the findings, published in the journal Nature.
White dwarfs are the fiery hot, burnt-out remains of dead stars. Janus is scolding hot, burning at a mighty 35,000 degrees Celsius (63,032 Fahrenheit), according to observations at NASA’s Neils Gehrels Observatory.
Janus used to be a star, like our Sun – which will begin evolving into a white dwarf in five billion years after becoming a red giant.
Caiazzo had originally been searching for highly magnetised dwarf stars when she found Janus. It stood out because of its rapid changes in brightness, so Caiazzo decided to investigate further.
With observations made from California, the Canary Islands, and Hawai’I, the dwarf’s dramatic double face was finally revealed.
Caiazzo and her team then used an instrument called a spectrometer to take the star’s light and spread its wavelengths out into a rainbow. This technique reveals which chemicals are present – helping the team work out that the brighter side of the dwarf is formed by hydrogen (with no traces of helium), while the other side was composed entirely of helium.
This baffled the scientists. While they are not yet able to provide an explanation for this phenomenon, they have some theories.
“Some white dwarfs transition from being hydrogen- to helium-dominated on their surface,” said Caiazzo. “We might have possibly caught one such white dwarf in the act.”
As to why one side of the white dwarf may transition before the other, the team speculates that magnetic fields may be involved. Magnetic fields can prevent materials mixing – so if there is a stronger magnetic field on one side of the star, then less mixing would mean more hydrogen.
The helium side’s bubbly appearance implies that the mixing of materials may have destroyed the thin layer of hydrogen on the surface, exposing the helium beneath.
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