NGC 3201 (also known as Caldwell 79) is a low galactic latitude
globular cluster
A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...
in the southern
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
of
Vela. It has a very low central concentration of stars.
This cluster was discovered by
James Dunlop
James Dunlop FRSE (31 October 1793 – 22 September 1848) was a Scottish astronomer, noted for his work in Australia. He was employed by Sir Thomas Brisbane to work as astronomer's assistant at his private observatory, once located at Param ...
on May 28, 1826 and listed in his 1827 catalogue. He described it as "a pretty large pretty bright round nebula, 4 or 5 diameter, very gradually condensed towards the centre, easily resolved into stars; the figure is rather irregular, and the stars are considerably scattered on the south".
[
The ]radial velocity
The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...
of this cluster is unusually high at 490 km/s, larger than any other cluster known. This corresponds to a peculiar velocity
Peculiar motion or peculiar velocity refers to the velocity of an object relative to a ''rest frame''—usually a frame in which the average velocity of some objects is zero.
Galactic astronomy
In galactic astronomy, peculiar motion refers to t ...
of 240 km/s. While high, this is lower than the escape velocity
In celestial mechanics, escape velocity or escape speed is the minimum speed needed for an object to escape from contact with or orbit of a primary body, assuming:
* Ballistic trajectory – no other forces are acting on the object, such as ...
of the Milky Way
The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...
galaxy.[ It is located at a distance of 16,300 ]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 from the Sun
The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
and has an estimated mass of 157,000 times the mass of the Sun
The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies a ...
.[ This cluster is about 10.24 billion years old.][
The stellar population of this cluster is inhomogeneous, varying with distance from the core. The ]effective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...
of the stars shows an increase with greater distance, with the redder and cooler stars tending to be located closer to the core. As of 2010, this is one of only two clusters (including Messier 4
Messier 4 or M4 (also known as NGC 6121 or the Spider Globular Cluster) is a globular cluster in the constellation of Scorpius. It was discovered by Philippe Loys de Chéseaux in 1745 and catalogued by Charles Messier in 1764. It was the first g ...
) that shows a definite inhomogeneous population.[
]
Black holes
Because NGC 3201 is a less dense globular cluster, far from undergoing core collapse, it is believed to harbor a substantial black hole
A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. Th ...
population in its core.
Indeed, a few black holes have been detected in this cluster, orbiting nearby stars.
In a study from 2022,Hubble Space Telescope
The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...
and the European Space Agency's Gaia spacecraft
''Gaia'' was a space observatory of the European Space Agency (ESA) that was launched in 2013 and operated until March 2025. The spacecraft was designed for astrometry: measuring the positions, distances and motions of stars with unprecedented ...
indicated that NGC 3201 has a sub-cluster of stellar mass black holes, with a total mass of roughly a thousand solar masses. The same study showed, with dynamical simulations, that this sub-cluster could contain nearly a hundred black holes.
Gallery
Caldwell 79.jpg, Astronomers discovered a black hole at the heart of NGC 3201.
Artist’s impression of the black hole binary system in NGC 3201.jpg, Artist's impression of the black hole binary system in NGC 3201.La Silla Observatory
La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory (ESO). Several other telescopes are also located at the site and are partly maintained by ESO. The observato ...
See also
* List of nearest black holes
This is a list of known black holes that are close to the Solar System.
It is thought that most black holes are solitary, but black holes in binary or larger systems are much easier to detect. Solitary black holes can generally only be detected b ...
References
External links
Globular Cluster NGC 3201 at SEDS pages
*
NGC 3201
at ''DOCdb'' (Deep Sky Observer's Companion)
{{DEFAULTSORT:NGC 3201
Globular clusters
Vela (constellation)
3201
079b
18260501