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.
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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).
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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.
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