Behold VFTS 352, the hottest and most massive “overcontact binary” star system ever discovered. The two stars, which are so close that they’re touching, feature a combined mass 57 times that of our Sun. Astronomers say it’s a unique stellar relationship that will culminate in a rather dramatic finish.
This unusually large contact binary was discovered by an international team of astronomers using the ESO’s Very Large Telescope. Located 160,000 light-years away, it’s comprised of two twin stars that orbit each other in a little over 24 hours. The stars are so close that their surfaces overlap, creating a stellar bridge between them.
This won’t end well (ESO/L. Calçada)
Remarkably, their cores are only 7.4 million miles (12 million kilometres) apart (that’s roughly 20 lunar distances). With a mass 57 times greater than the Sun, and a scorching surface temperature exceeding 40,000 degrees Celsius, it’s the hottest and most massive overcontact binary ever discovered. The details of this extraordinary finding can now be found in the Astrophysical Journal.
This kissing pair is unique in that both stars are roughly equal in terms of size. Other similar systems feature a star that’s significantly larger than the other, resulting in the cannibalisation of the smaller object. But these two, with their roughly equal mass, may actually be sharing their cosmic material with each other. Astronomers speculate that the twin stars of VFTS 352 are swapping about 30 percent of their stellar stuff, a phenomenon known as “internal mixing.”
Location of VFTS 352 in the Large Magellanic Cloud (ESO)
Due to their volatile nature, systems like these don’t last long. Astronomers are actually quite fortunate to have discovered this system, which could meet its end in one of two ways. The ESO explains:
The first potential outcome is the merging of the two stars, which would likely produce a rapidly rotating, and possibly magnetic, gigantic 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,” says the lead scientist of the project, Hugues Sana, of the University of Leuven in Belgium.
The second possibility is explained by the lead theoretical astrophysicist in the team, Selma de Mink of University of Amsterdam: “If the stars are mixed well enough, they both remain compact and the VFTS 352 system may avoid merging. 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.”
Interestingly, systems like VFTS 352, with its tremendous internal heat, perform a critical role in the evolution of galaxies, and are thought to be a major producer of elements like oxygen. [ ESO ]
Read the entire scientific study in the Astrophysical Journal: “Discovery of the massive overcontact binary VFTS 352: Evidence for enhanced internal mixing.”