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This is one of the strangest star systems astronomers have ever found

An illustration of two contacting stars — part of the newly discovered bizarre five-star system.
An illustration of two contacting stars — part of the newly discovered bizarre five-star system.
(ESO)

Scientists have discovered an absolutely bizarre star system about 250 light years away, in the constellation Ursa Major.

The system (officially known as 1SWASP J093010.78+533859.5) features five stars that are all gravitationally bound together. Two orbit each other in what's called a contact eclipsing binary, meaning they're so close together that they actually share an atmosphere, with gases flowing between them.

Another two stars also orbit each other, but at a much greater distance — about 1.8 million miles, which is more than twice the diameter of the sun. Another star hangs out near that pair, but doesn't appear to orbit them.

(Marcus Lohr)

Systems that include five stars gravitationally bound together are rare, though not unprecedented (astronomers have actually found systems that include as many as six stars). But this is the first one ever found that includes multiple pairs of stars orbiting each other.

The discoverers of the strange system — a team of astronomers from Open University in the UK and elsewhere — presented all these discoveries in a new paper published today in the journal Astronomy & Astrophysics. Thanks to George Dvorsky at io9 for bringing it to our attention.

How astronomers study stars 250 light-years away

(Centre de Données astronomiques de Strasbourg/SIMBAD)

From a single telescope on Earth, all these stars would basically look like a single blob of light, as in the photo above. So to discern the behavior of the stars within the blob — and figure out exactly how many there are — astronomers have to do a bit more analysis.

In this case, they used a series of telescopes in the Canary Islands and South Africa to track exactly how much light was coming from the blob over time. If two stars orbit each other such that one occasionally eclipses the other — blocking it from our view — it'll cause the total amount of light coming from a system to dip regularly. (This is very similar to a common method astronomers use to find exoplanets.)

(ESO/L. Calçada)

Using this method, the astronomers initially calculated that the blob of light was actually two stars orbiting each other. Eventually, however, they discovered that the data included a second, distinct dip in the amount of light coming to us — indicating a second pair of stars orbiting each other. Finally, they calculated that a fifth star is also present, though it doesn't cross in front of any of the others, and so it doesn't cause another dip.

The astronomers say it's possible this bizarre system could be home to a host of planets orbiting one or multiple stars. They believe the stars may have originally formed from a single disk of gas, which was later broken into distinct clumps — and by further studying the system and its formation, they may learn more about the dynamics of star creation in general.