Two-faced star seems to have one hydrogen side and one helium side

Astronomers have discovered a two-faced star the place both sides has a unique composition. This white dwarf star, nicknamed Janus after the Roman god of doorways and transitions, is the primary of its sort ever noticed.

Jeremy Heyl on the University of British Columbia in Canada and his colleagues noticed Janus utilizing the Zwicky Transient Facility in California, after which took extra observations utilizing a number of different telescopes. The observations indicated that one facet of the star was made up fully of hydrogen, and the opposite facet fully of helium. It is greater than 1300 gentle years from Earth and rotates about as soon as each quarter-hour.

We know that the complete floor of some white dwarfs can transition from helium to hydrogen and again to helium once more, however we’ve by no means definitively caught one in the course of this transformation earlier than. The mechanism behind it stays murky.

“It seems likely to be connected with a magnetic field in the star that’s a bit stronger on one side than the other, but the data itself doesn’t show evidence for a very strong magnetic field,” says Heyl. “So we still don’t completely understand what’s going on.”

If there’s such a magnetic discipline, it might suppress the star’s convection, or inner churning, solely on the facet the place it’s stronger. White dwarfs are made primarily of hydrogen and helium, so the lighter hydrogen would naturally float to the floor of the facet with no convection, whereas on the opposite facet the extra ample helium would bubble as much as the highest.

“If it was at the distance of the moon, you’d be able to clearly see these blotches from convection and it would look like one half is around 15 per cent brighter than the other,” says Heyl. “Its temperature is about five times the temperature of the sun so it would appear incredibly dazzling to the eye – it would be uncomfortable to look at.”

The indisputable fact that we’ve searched a lot of the cosmos and solely discovered one in all these stars implies that these objects are in all probability comparatively uncommon. It additionally took an unbelievable coincidence for us to have the ability to establish it – the axis of rotation simply occurs to be perpendicular to the divide between the helium face and the hydrogen face, and we simply occur to be positioned face-on to the star.

Now that they’ve had this stroke of luck, the researchers hope to take extra detailed information on Janus to determine how precisely its inner dynamics work. This star might be the important thing that unlocks the reason of this unusual section of white dwarf evolution.