Astronomers Have Discovered an Exotic Quintuple Star System

Researchers at the Open University, UK, have found an unusual set of five gravitationally bound stars they say should “put the makers of Star Wars to shame.” The system, labelled as 1SWASP J093010.78+533859.5, contains two sets of eclipsing binary stars, and a fifth single star. Quintuple star systems have been found before, but this is the first time researchers have ever seen a pair of eclipsing binaries inside a five-star system. The details of this astonishing discovery have been issued in the science journal Astronomy& Astrophysics.

Artistic impression. Smaller orbits are not displayed to scale relative to the larger orbit, as the binary components would be too close together to differentiate. The inset images are to scale, with an image of the Sun for contrast. The blue dotted line marks the orbital path of the two pairs of stars. The fifth star, whose location is unclear, is to the right of the left pair. (Image and caption credit: Marcus Lohr).

The system, situated 250 light-years from Earth, was initially spotted in archived data from the SuperWASP (Wide Angle Search for Planets) project, an arrangement of small, low-cost cameras at the Observatorio del Roque de los Muchachos in the Canary Islands, and also at the Sutherland Station of the South African Astronomical Observatory. Over the years, these cameras spasmodically measure the brightness of distinct stars, letting researchers to track their brightness over time. Using a method parallel to how astronomers discover distant exoplanets, a group of astronomers directed by Marcus Lohr of the Open University, UK, was able to observe and study changing light curves to expose the exceptional details of this amazing quintuple star system.

Two stars of this system are a contact eclipsing binary—a stellar formation in which two stars are orbiting so narrowly together than they share the same atmosphere; from a distance, it would appear as though they’re touching. Contact binaries aren’t uncommon, but this one is distinctive in that it features mostly short orbital period; it takes just six hours for these two stars to circle one another.

As for the other binary, its two separate stars are positioned about 21 billion kilometers from its companion binary, which is a distance slightly larger than Pluto’s orbit around the Sun.

Further study shown a fifth star, up to two billion kilometers away from the separate binary, but it’s not creating any additional eclipses. By studying the system’s light curves and their spectra, the scientists confirmed that they’re all gravitationally bound together in a lone system. A pre-print version can be found at arXiv.