Astronomers have spotted a bizarre star system in which six stars orbit and eclipse each other when viewed from our solar system.
Using data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which is designed primarily to find exoplanets, Benjamin Montet at the University of New South Wales, Australia, and his colleagues observed the system known as TIC 168789840, located 1900 light years away.
TESS searches for alien worlds by looking for the dip in a star’s light when a planet passes in front. But this method means it can also spot so-called eclipsing binaries – where stars in a double system pass in front of each other from our point of view.
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“This system defied expectations at first, because there were lots and lots of eclipses,” says Montet.
With the help of TESS, the team was able to piece together the structure of the system. Four of the stars are in two sets of two. These sets, A and C, each have two stars that orbit each other in 1.6 and 1.3 days respectively, and the two sets orbit each other every 3.7 years.
Then another binary, labelled B, has two stars that orbit each other every 8.2 days. B orbits the A and C quadruple roughly every 2000 years.
What’s most impressive about the system is that we see it almost exactly edge on, so all of the stars cross each other from our point of view. “There are a few [other known] six-star systems, but this is the only one to have three sets of eclipses,” says Montet.
Aside from being fascinatingly odd, the system could prove scientifically useful. “We don’t really understand why [some] stars become binaries and others don’t,” says Montet. “This system could provide avenues to help understand that.”
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