An extremely rare five-star system has been found that astronomers say is the first of its kind. It is unique for having two sets of two stars in relatively close orbit around a common center of gravity, and a fifth star near one of the pairs. While other quintuple systems have been spotted previously, nothing has been seen quite like this, with the stars so close to each other.
The discovery, presented at the UK National Astronomy Meeting in Llandudno, Wales, was made by the SuperWASP (Wide Angle Search for Planets) project, which images the whole sky every few minutes using cameras in the Canary Islands and South Africa. Given the catchy title 1SWASP J093010.78+533859.5, the system is located 250 light-years from Earth in the constellation Ursa Major.
Two of the binary stars orbit so close, less than the diameter of the Sun, that they share an atmosphere – known as a contact binary. The other pair of stars are separated from each other by 3 million kilometers (1.9 million miles) and are an eclipsing binary, where the orbit of the stars as viewed from Earth causes constant transits.
These two orbiting pairs are separated by about 21 billion kilometers (13 billion miles), greater than Pluto's orbit around our Sun, but scientists were surprised to find a fifth star 2 billion kilometers (1.2 billion miles) from the detached binary. More than 80% of all stars in the universe could be part of binary or multiple systems, but this is the first found in this specific configuration, with two orbiting binaries and an additional fifth star.
This artist’s impression shows the five-star system. The smaller orbits of the binary stars are exaggerated in size, otherwise they would not be visible at this scale. Credit: Marcus Lohr
The researchers speculate in their paper that the famous five, all thought to be smaller than the Sun, may have formed from the “fragmentation” of a single large disk of dust and gas up to 10 billion years ago, which is why they are all so close now. They also did not rule out the possibility that one or more of the stars may have planets, which would produce some odd sights in the sky.
“Any inhabitants would have a sky that would put the makers of Star Wars to shame – there could sometimes be no fewer than five Suns of different brightnesses lighting up the landscape,” Marcus Lohr from the Open University said in a statement. "Days would have dramatically varying light levels as the different stars were eclipsed. They would though miss out on night for a large part of their ‘year’, only experiencing darkness (and a night sky) when the stars were on the same side of their world.”
The system will be studied further to hopefully shed some light on how it, and others like it, came into being.