Astronomers in Britain have discovered a quintuple star system, in which two binary star pairs and a lone fifth star are all gravitationally bound together.
While astronomers say around a third of the stars in the universe are in pairs or inhabit multiple systems, five stars is a single system is rare — although not entirely unknown.
The system with the unwieldy name of 1SWASP J093010.78+533859.5 was detected in data collected by the SuperWASP (Wide Angle Search for Planets) project, in which relatively simple and low-cost cameras in South Africa and the Canary Islands complete an entire image scan of the sky every few minutes.
The astronomers analyzed the light coming from the system, about 250 light years away from us in the constellation of Ursa Major, to detect periodic dips in intensity as the stars passed in front of each other from our point of view here on Earth.
The first analysis revealed a contact eclipsing binary, two stars orbiting each other so closely they share an outer atmosphere.
However, that didn't completely explain the light dips seen, and the researchers reanalyzed the data and discovered a second binary pair of well-separated stars.
The two binary pairs are about 13 billion miles apart, about the distance of Pluto's orbit around our sun.
When the astronomers conducted further spectroscopic observations of the four stars in an attempt to gather more detail on each, an unexpected fifth star was revealed about 1.2 billion miles from the more separated of the binary pairs, astronomers at the Open University reported in the journal Astronomy & Astrophysics.
The light measurements and the spectrographic data confirmed all five are gravitationally bound in a single system, they said.
"This is a truly exotic star system," says study leader Marcus Lohr. "In principle there's no reason it couldn't have planets in orbit around each of the pairs of stars.
"Any inhabitants would have a sky that would put the makers of Star Wars to shame," he says, a reference to the fictional movie planet Tatooine and its two suns.
The astronomers were struck by the fact that the two binary pairs of stars appear to be orbiting in the same plane.
This is evidence that all four may have formed from the same single disk of dust and gas, they say.
While all five stars in the quintuple system are smaller and cooler than our sun, their collective brightness is such that the system can be observed from Earth with even a small telescope, they add.