Sunday, October 25, 2015

What Is the Fate of the Hottest and Most Massive Touching Double Star?

This artist’s impression shows VFTS 352 — the hottest and most massive double star system to date where the two components are in contact and sharing material. The two stars in this extreme system lie about 160 000 light-years from Earth in the Large Magellanic Cloud. This intriguing system could be heading for a dramatic end, either with the formation of a single giant star or as a future binary black hole.  Credit: ESO/L. Calçada

The double star system VFTS 352, located about 160,000 light-years away in the Tarantula Nebula is heading for catastrophe. The two stars, found lately by an international team of astronomers, will face a cataclysmic fate, but how exactly their life will end is yet to be determined. “Theorists like me are debating about the future of the system,” Selma E. De Mink of the University of Amsterdam, one of the co-discoverers of this system, told astrowatch.net.

VFTS 352 is the hottest and most massive double star with components so close that they touch each other. The system is composed of two very hot, bright and massive stars that orbit each other in little more than a day. The centers of the stars are separated by just 12 million kilometers. The stars are so close that their surfaces overlap and a bridge has formed between them.

“The two stars are so close that they touch each other. They even share 30 percent of their material. It is the hottest and most massive ‘overcontact’ binary,” De Mink said.

Astronomers predict that VFTS 352 will face a cataclysmic fate in one of two ways. The first potential outcome is the merging of the two stars, which would likely produce a rapidly rotating, and possibly magnetic, gigantic single star. The second possibility is that they will form a binary black hole.

According to De Mink, classic models predict that the two stars will melt together forming one new fast-rotating mega star. However, some of the newer models try to account for the fact that the two stars are forced to co-rotate with each other. These new models predict that the stars are internally very disturbed. In their center the stars fuse hydrogen in to helium. If the stars are very disturbed, the models predict that they can mix helium all the way to the surface. If this is true, the models predict that the stars would slowly keep shrinking. In this scenario the system would eventually form two black holes in a binary system.

Regardless of how VFTS 352 meets its demise, this system has already provided astronomers with valuable new insights into the poorly understood evolutionary processes of massive overcontact binary star systems.

The system’s name indicates that it was observed as part of the VLT FLAMES Tarantula Survey, which utilized the FLAMES and GIRAFFE instruments on European Southern Observatory’s (ESO) Very Large Telescope (VLT) to study over 900 stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). The survey is helping to answer many fundamental questions concerning how massive stars are affected by rotation, binarity and the dynamics in dense star clusters.

The research was presented in a paper in entitled “Discovery of the massive overcontact binary VFTS 352: Evidence for enhanced internal mixing”, by L. Almeida et al., in the Astrophysical Journal.

1 comment:

  1. Fascinating as Astrophysics always is , thanks for sharing this with us all ...

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