Using data from ESA’s Gaia mission, astronomers discovered a nearby binary system of massive stars orbiting a dormant star-derived black hole over a period of 11.6 years. The black hole’s estimated mass (33 solar masses) is significantly larger than all known stellar-mass black holes in the Milky Way and within the mass range of extragalactic black holes detected by gravitational waves.
Locations of the first three black holes discovered in the Milky Way by ESA’s Gaia mission. Image credit: ESA/Gaia/DPAC.
The binary star system in question is named Gaia BH3 and is located 1,926 light-years from Earth in the constellation Aquila.
Also known as Gaia DR3 4318465066420528000, LS II +14 13, and 2MASS J19391872+1455542, it consists of an old, very metal-poor giant star and a dormant stellar-mass black hole.
Gaia BH3 is the third dormant black hole discovered by ESA’s interstellar mapping satellite Gaia.
“This is the kind of discovery that only happens once in a research career,” said Dr. Pasquale Panuzzo, an astronomer at the CNRS and the Paris Observatory.
“So far, black holes this large have only been detected in distant galaxies by the LIGO-Virgo-KAGRA collaboration, thanks to observations of gravitational waves.”
The average mass of the known stellar-origin black holes in our galaxy is about 10 times the mass of the Sun.
Astronomers face the pressing problem of explaining the origin of black holes as large as Gaia BH3.
Our current understanding of how massive stars evolve and die does not immediately explain how this type of black hole could be born.
Most theories predict that as massive stars age, a significant portion of their material is shed by powerful winds. Eventually, it will be partially blown into space when it explodes as a supernova.
The remainder of the core shrinks further, becoming either a neutron star or a black hole, depending on its mass.
It is extremely difficult to explain a core large enough to eventually become a black hole 30 times the mass of the Sun. But the clues to solving this mystery may lie very close to Gaia BH3.
The star, which orbits Gaia BH3 at about 16 times the distance between the Sun and Earth, is quite unusual and is an ancient giant that formed during the first two billion years after the Big Bang, when our galaxy began to form. It’s a star.
It belongs to the family of galactic stellar halos, which move in the opposite direction to the stars in the galactic disk.
Its orbit indicates that the star was probably part of a small galaxy, or globular cluster, that was swallowed up by the Milky Way more than 8 billion years ago.
This companion star contains almost no elements heavier than hydrogen or helium, indicating that the massive star that became Gaia BH3 may also have been extremely poor in heavy elements.
For the first time, the theory that the massive black holes observed in gravitational wave experiments were created by the collapse of primordial massive stars lacking heavy elements has been confirmed.
These early stars may have evolved differently from the massive stars we see in our galaxy today.
The composition of the companion star can also reveal the formation mechanism of this surprising binary system.
“We were surprised that the chemical composition of the companion star is similar to that seen in older, metal-poor stars in the Milky Way,” said Dr. Elisabetta Cuffo, an astronomer at the CNRS and the Paris Observatory.
“There is no evidence that this star was contaminated by material ejected from the supernova explosion of the massive star that became BH3.”
“This may suggest that the black hole acquired a mate from another star system for the first time after its birth.”
of the team paper be published in a magazine astronomy and astrophysics.
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P. Panuzzo other. (Gaia collaboration). 2024. Gaia astronomical measurements prior to release discovered a dormant black hole with the mass of 33 solar masses. A&A, in press. doi: 10.1051/0004-6361/202449763
Source: www.sci.news
