1/ Most massive stellar #BlackHole in our galaxy found! With 33 times the mass of the Sun, this is the most massive black hole formed after the collapse of a star that we've found so far in the #MilkyWay.
ESA's Gaia mission found it via the wobble it induces on a star orbiting it, and data from ground-based telescopes helped confirm its mass and elucidate how it formed.
2/ Stellar black holes are usually 10, maybe 20 times more massive than the Sun. More massive ones had been found in other galaxies with a different method (gravitational waves) but explaining how they form is tricky.
Massive stars lose a lot of material throughout their lifetime due to powerful stellar winds, so it's not easy to leave behind a large enough remnant.
3/ But if the progenitor star is very poor in elements heavier than hydrogen and helium, then these winds are not so powerful and the star may end its life with enough leftover material to form a more massive black hole.
Using data from telescopes like ESO's VLT the team found that the companion star is indeed very poor in these elements. Since stellar pairs typically share a similar composition, it is very likely that the parent star that formed the black hole was also poor in heavy elements.
4/ To clarify: this is not the most massive black hole in our galaxy –– that's Sagittarius A*, lurking 27,000 light-years away at the centre of the galaxy, with 4 million times the mass of the Sun. But Sgr A*, like other supermassive black holes at the centre of other galaxies, have different formation mechanisms.
This new black hole, dubbed Gaia BH3, is comparatively closer, just 2000 light-years away, and it will help us better understand how massive stars die.
There also can be a hypothesis that the stellar companion might be a captured one, like Neptune had captured Triton. They might not have evolved together.
@breakpoint This is indeed possible. This system might belong to a recently identified stream of stars dubbed ED-2, which could be the disrupted leftovers of an old globular cluster –– a densely packed group of lots of stars. In this context, a capture scenario is possible. The chemical composition of the stars in this stream seems to be similarly poor in heavy elements as the companion of the black hole, so the idea that the black hole might result from this kind of star remains viable.
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