Massive stars in metal-poor environment often have close partners, scientists discover

Massive stars in metal -poor galaxies often have narrow partners, as well as massive stars in our milky way rich in metal. This was discovered by an international team of 70 astronomers led by scientists from Belgium, the Netherlands and Israel. They used the very large European telescope in Chile to monitor the speed of massive stars in the small magellanic cloud.

Researchers have published their results in Natural astronomy.

Over the past 20 years, astronomers know that many massive stars of the Milky Way rich in metals have a partner. In recent years, it has become clear that the interaction between these partners is important for the evolution of massive stars. However, so far, astronomers did not know if massive stars in metal -poor galaxies could also be part of a binary system. Now it turns out that this is indeed the case.

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“We used the Magellanic little cloud as a time to go back in time,” explains Hugues Sana from Ku Leuven (Belgium). “The Magellanic little cloud has an environment of metallicity representative of that of distant galaxies when the universe was only a few billion years.”

Studying the massive stars outside the Milky Way is difficult because the stars are far away and we receive little light. The researchers used the Flames spectrograph on the very large telescope of the Southern European Observatory in Chile. It is one of the largest telescopes on the earth. Flames has 132 optical fibers, each can be directed to a different star, which can then be observed simultaneously.

Accelerate and decelerate

Over a period of three months, the researchers observed the acceleration and deceleration of 139 massive stars of type O at nine times different. These stars have masses between 15 and 60 times those of our sun. They are hot, shine brilliantly and put an end to their lives in supernova explosions.

In the process, the kernel of the star collapses in a black hole. The results show that more than 70% of the stars observed accelerate and die. It is a sign for a neighboring partner.

“The fact that the massive stars of the Magellanic little cloud have a partner suggest that the first stars of the universe, which we suspected were also massive, also had partners,” said co-author Julia Bodensteiner of the University of Amsterdam (Netherlands). “Perhaps some of these systems end up like two black holes in orbit. It is an exciting thought.”

Researchers have planned to observe the same stars sixteen times more in the near future. They aim to rebuild the precise orbits of the binary stars, to determine the masses of their components and to study the nature and the properties of the companion star.

“Using our measures, our cosmologists and our astrophysicists who study the young universe poor in metal will then be able to count on our knowledge of massive binary stars with greater confidence,” concludes Tomer Shenar from the University Tel Aviv (Israel).