Astronomers have made a new stunning discovery in our Galaxy: a massive stellar black hole, in the constellation of Aquila. A stellar black hole, also referred to as collapsar, is a black hole formed due to the gravitational collapse of a massive star. Typically, these have a mass ranging from 5 to tens of times that of our Sun, but never before had such a massive stellar black hole been detected in the Milky Way.
The discovery was made possible through the collaboration between the European Space Agency’s Gaia mission and ESO’s Very Large Telescope (VLT).
The research study, published today in Astronomy & Astrophysics, is led by Gaia collaboration member Pasquale Panuzzo, an astronomer from the National Centre for Scientific Research (CNRS) at the Observatoire de Paris.
“This is the kind of discovery you make once in your research life.”
— Pasquale Panuzzo, astronomer at the French National Centre for Scientific Research (CNRS)
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The discovery
The newly discovered celestial object, called Gaia BH3, is 33 times the mass of the Sun and is relatively close to us, 2000 light-years, becoming the second-closest known black hole to Earth. The previous known most massive stellar black hole, Cygnus X-1, only reaches 21 solar masses.
The discovery of BH3 was almost accidental; in fact, the team was in the process of reviewing observations from Gaia in preparation for an upcoming data release. To confirm the discovery, and especially the size of the black hole, researchers used data from ground-based observatories, including the Ultraviolet and Visual Echelle Spectrograph (UVES) instrument on ESO’s VLT.
The European Southern Observatory’s Very Large Telescope, located in Chile’s Atacama Desert, is the world’s most advanced visible-light astronomical observatory.
The discovery of similar massive black holes outside our Galaxy, suggests that these black holes may form from the collapse of metal-poor stars, which contain very few elements heavier than hydrogen and helium.
Stars in binary systems often share similar compositions. Indeed, BH3’s companion, identified through UVES data, is a highly metal-poor star, affirming that the star responsible for forming BH3 was also metal-poor, as anticipated.
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Gaia mission
Gaia is a European mission aimed at creating the largest, most precise three-dimensional map of our Galaxy. To do so it is observing nearly two billion objects, discovering hundreds of thousands of new celestial objects, such as extra-solar planets and brown dwarfs, and as many asteroids within our own Solar System.
The spacecraft was launched in 2013 on a Russian Soyuz-STB/Fregat-MT from the European Spaceport, in French Guiana. Gaia was placed in the Sun-Earth Lagrange point L2, 1.5 million kilometers from our planet.
The European satellite is equipped with two optical telescopes that work with three scientific instruments to precisely determine the location of stars and their velocities and to split their light into a spectrum for analysis.
The Gaia mission is scheduled to conclude in 2025. At its conclusion, it will stand as one of the most significant astronomical missions ever, having conducted the largest-ever collection of astrophysical data for stars in the Milky Way.
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