Gaia BH3 (Gaia DR3 4318465066420528000) is a

binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...

consisting of a

metal-poor In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-dark) matter in the universe is either hydrogen or helium, and astronomers ...

giant star A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsp ...

with spectral type G and a

stellar-mass black hole A stellar black hole (or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. They are the remnants of supernova explosions, which may be ...

. Gaia BH3 is located 1926

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s away ( away) in the constellation of Aquila. Gaia BH3 is the first black hole discovered from preliminary Gaia DR4 astrometric data. The black hole and star orbit the system

barycentre In astronomy, the barycenter (or barycentre; ) is the center of mass of two or more bodies that orbit one another and is the point about which the bodies orbit. A barycenter is a dynamical point, not a physical object. It is an important con ...

every 11.6 years, with an orbital distance ranging from . The black hole's mass is , the heaviest known stellar black hole in the Milky Way. The black hole Gaia BH3 is the second known stellar black hole more massive than about 10 (with the first being

Cygnus X-1 Cygnus X-1 (abbreviated Cyg X-1) is a galactic X-ray source in the constellation Cygnus and was the first such source widely accepted to be a black hole. It was discovered in 1964 during a rocket flight and is one of the ...

). The mass of Gaia BH3 is quite similar to the mass of merging

binary black hole A binary black hole (BBH), or black hole binary, is an astronomical object consisting of two black holes in close orbit around each other. Like black holes themselves, binary black holes are often divided into binary stellar black holes, formed e ...

s found via

gravitational waves Gravitational waves are oscillations of the gravitational field that travel through space at the speed of light; they are generated by the relative motion of gravitating masses. They were proposed by Oliver Heaviside in 1893 and then later by H ...

. These massive black holes were suspected to be formed by

stars and the fact that Gaia BH3 has a metal-poor companion strengthens this conclusion. Gaia BH3 was found to be part of a disrupted

star cluster A star cluster is a group of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters, tight groups of ten thousand to millions of old stars which are gravitationally bound; and open cluster ...

of low mass and this star cluster is today a

halo HALO, halo, halos or haloes may refer to: Most common meanings * Halo (optical phenomenon) * Halo (religious iconography), a ring of light around the image of a head * ''Halo'' (franchise), a sci-fi video game series (2001–2021) Arts and en ...

stellar stream In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as ...

, called ED-2. This stellar stream is very old, with an age comparable to the globular cluster Messier 92. This means that Gaia BH3 likely formed more than 13 billion years ago and the black hole might have formed via direct collapse of a massive star. Alternatively the black hole could have formed via binary interaction inside the star cluster. The ED-2 star cluster has a mass between 2,000 and 42,000 .

Discovery

Gaia BH3 was identified in

astrometric Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. History ...

observations with

Gaia In Greek mythology, Gaia (; , a poetic form of ('), meaning 'land' or 'earth'),, , . also spelled Gaea (), is the personification of Earth. Gaia is the ancestral mother—sometimes parthenogenic—of all life. She is the mother of Uranus (S ...

, during an analysis in preparation for Data Release 4. It was announced with the publication of a

scientific paper Scientific literature encompasses a vast body of academic papers that spans various disciplines within the natural and social sciences. It primarily consists of academic papers that present original empirical research and theoretical ...

in the journal ''

Astronomy & Astrophysics ''Astronomy & Astrophysics (A&A)'' is a monthly peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics. It is operated by an editorial team under the supervision of a board of directors re ...

'' on 16 April 2024.

References

{{2024 in space Aquila (constellation) G-type main-sequence stars Stellar black holes Astrometric binaries 20240416

Discovery

See also

References