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Hottest, most massive pair of joined stars is heading for spectacular disaster

Two suns are spotted touching, a dramatic last contact before the end. But will they merge into one or follow "a new evolutionary path" leading to binary black holes?

Michael Franco
Freelancer Michael Franco writes about the serious and silly sides of science and technology for CNET and other pixel and paper pubs. He's kept his fingers on the keyboard while owning a B&B in Amish country, managing an eco-resort in the Caribbean, sweating in Singapore, and rehydrating (with beer, of course) in Prague. E-mail Michael.
Michael Franco
2 min read

Two giant balls of fire touching, the surfaces overlapping and forming a bridge -- the overcontact binary is a rare and dramatic class of stars. Now, a team of researchers has spotted an overcontact binary that's the most massive and hottest that's yet been observed. The two stars orbit each other in less than 24 hours.

Called VFTS 352, the double star system is located roughly 160,000 light-years away in the Tarantula Nebula. The combined stars have a mass approximately 57 times that of our own sun and surface temperatures soar above 40,000 degrees Celsius (about 70,000 degrees Fahrenheit). For comparison, the temperature of our sun's photosphere, the layer we see as sunlight, is about 5,500 degrees Celsius (10,000 degrees Fahrenheit).

The pair was observed using the European Southern Observatory's Very Large Telescope (VLT), located in northern Chile.

contact-binary-stars.jpg
An artist's impression of what the two massive touching stars could look like. ESO

Catching this solar kiss is rare because it's pretty certain that both suns won't last in this configuration. The researchers predict an end to the system in one of two ways.

First, the stars could merge, forming a gargantuan single star. "If it keeps spinning rapidly it might end its life in one of the most energetic explosions in the universe, known as a long-duration gamma-ray burst," Hugues Sana of the University of Leuven in Belgium said in a statement. Sana is the lead scientist of the project that found the star pair.

The second option is that the two stars don't merge and they end their lives explosively.

"If the stars are mixed well enough, they both remain compact and the VFTS 352 system may avoid merging," said the team's lead theoretical astrophysicist, Selma de Mink of the University of Amsterdam.

"This would lead the objects down a new evolutionary path that is completely different from classic stellar evolution predictions. In the case of VFTS 352, the components would likely end their lives in supernova explosions, forming a close binary system of black holes. Such a remarkable object would be an intense source of gravitational waves." Gravitational waves are, in essence, ripples in the fabric of spacetime.

In either case, the end for the stars is certain to be spectacular.

The findings of the research team have been published in The Astrophysical Journal.