Scientists measured the mass of the largest and hottest star in the Milky Way

A team of scientists from the Instituto de Astrofísica de La Plata (IALP, CONICET-UNLP) managed to measure the mass of the largest and hottest star of which there is information so far in our galaxy, according to an article recently published in the American journal Monthly Notices of the Royal Astronomical Society. This was done with observations taken from Las Campanas Observatory.

“Massive stars are called all those that have, at the moment of birth, at least 8 times the mass of the Sun. The bigger they are, the faster they evolve, so they live less time than smaller ones,” said Cinthya Rodríguez, a CONICET fellow at the IALP and main author of the study.

“Let’s think that in the Milky Way there are about 100 billion stars in total, of which only a few thousand are massive. And of those, only 138 are known and described in detail. Their observation is much more difficult due to the places where they are located and because their existence is brief in astronomical terms”, added the specialist. Precisely, to this enormous list of stars, we must now add HM1 8, the star that the team of specialists managed to measure and characterize in detail thanks to the images obtained at Las Campanas Observatory, which is located in the mountains of the Atacama Desert, Chile.

“In reality, HM1 8 is an eclipsing binary system, that is, two stars that revolve around each other, blocking each other out. Located 9,000 light-years from Earth, the larger star has 34 times the mass of the Sun, 11 times its diameter, and a surface temperature 7 times higher,” said Rodrìguez.

Another fact that attracted the Argentine scientists is the great luminosity of HM1 8, since it shines 250,000 times more brightly than the energy emitted by the central star of the Solar System.

Regarding its age, Rodríguez and his team of collaborators were able to determine that it is about 2,000,000 years old, a time that places it more or less in the middle of its life, taking into account that such massive objects last less than 10,000,000 years, very little compared to smaller ones, whose existence reaches several billion years.

For his part, Gabriel Ferrero, IALP astronomer and co-author of the study, explained that at birth, a massive star enters a stage called “main sequence”, in which it spends most of its life.

“Then, the giant phase follows and, eventually and very quickly, it explodes and ends its existence as a gravitational collapse supernova, abruptly expelling almost all its material,” added the Argentine astronomer. Taking into account these parameters, everything indicates that HM1 8 is leaving its main sequence to become a giant.

“In the beginning, when the universe emerged, there were only two gases: hydrogen and helium. The rest of the elements, such as calcium, carbon, oxygen and more, were formed over time inside the stars, to shoot out into space every time one went out. Through this process, the atoms of our bodies were formed, hence the saying ‘we are stardust’. But not all stars are capable of producing them, but only the largest ones, among which is the HM1 8 system, of which we were now able to draw a very rigorous characterization and confirm that it is the most massive and hottest star of which we have precise measurements in the entire Milky Way”, concluded Ferrero.

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