An article published in “Astrophysical Journal” describes a research on a couple of very special stars. The binary system called VFTS 352 is in fact composed of two stars that are touching and these stars are the largest discovered to date in this situation. An international team of astronomers used ESO’s VLT (Very Large Telescope) to observe this double star, also to try to understand what kind of development could have.
The two stars in the VFTS 352 pair are class O, stars much larger than the Sun and therefore very hot and bright. In this case, the combined mass is about 57 times that of the Sun and the temperature on their surface is higher than 40,000° Celsius (72,000° Fahrenheit). The distance between the centers of the two stars is just 12 million kilometers (about 7.5 million miles).
The situation of couples such as VFTS 352 is called overcontact binaries. In these cases the two stars have very similar masses so there’s a balance that leads them to share part of their mass in the area where they touch. It’s a different case from that of the vampire stars, in which the mass of the two stars is different and one of the two sucks matter from its companion.
Systems such as VFTS 352 are rare because they have a short life. Astronomers want to keep watching this couple also to try to figure out its end. It’s possible that the two stars will end up merging but even if that doesn’t happen the life of stars so large is still short because they consume hydrogen at much higher speeds than the Sun.
If the two stars of VFTS 352 merge, they will produce a single giant star with a fast rotation that could have a high magnetic field. In this case, when the resulting star explodes, it will generate a long-duration gamma-ray burst, one of the most energetic events in the universe.
If the two stars of VFTS 352 keep on remaining at least partially independent, probably both will eventually explode. After those supernovae their nuclei will become very close black holes, creating a very intense source of gravitational waves. Currently, the observation of these waves is one of the main goals in the field of astrophysics.
It’s not yet possible to determine whether the two stars of VFTS 352 will merge and if that happens they can’t tell when. In astronomical terms, million years is a short time so it takes a lot of luck to find such an event in progress. VFTS 352 is still a very interesting couple to study to better understand overcontact binaries.
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