Intermediate-mass black hole

Intermediate-mass black hole

An Intermediate-mass black hole (IMBH) is a black hole whose mass is significantly more than stellar black holes (a few tens of the mass of the Sun) yet far less than supermassive black holes (a few millions of the mass of the Sun).

There is less evidence for their existence than for the other two types. Some ultra-luminous X ray sources (ULXs) in nearby galaxies are suspected to be IMBHs, with masses of a hundred to a thousand solar masses. [cite news
title=Black Hole Boldly Goes Where No Black Hole Has Gone Before
publisher=ESA News
date=January 3, 2007
] The ULXs are observed in star forming regions (e.g., in starburst galaxy M82cite journal
author=Patruno, A.; Portegies Zwart, S.; Dewi, J.; Hopman, C.
title=The ultraluminous X-ray source in M82: an intermediate-mass black hole with a giant companion
journal=Monthly Notices of the Royal Astronomical Society: Letters
url= | doi=10.1111/j.1745-3933.2006.00176.x
] , see external links for beautiful pictures of this galaxy), and are seemingly associated with young star clusters which are also observed in these regions. However only a dynamical mass measurement from the analysis of the optical spectrum of the companion star can unveil the presence of an IMBH as the compact accretor of the ULX.

Additional evidence for the existence of IMBHs can be obtained from observation of gravitational radiation, emitted by the compact remnant that orbits the IMBH. [cite journal| id=arxiv|astro-ph|0506181| title=Gravitational waves from remnants of ultraluminous X-ray sources| first= Clovis| last= Hopman| coauthors= Simon Portegies Zwart | journal=Mon.Not.Roy.Astron.Soc.Lett.| volume= 363| year=2005| pages= L56–L60| doi=10.1111/j.1745-3933.2005.00083.x] Also, the M-sigma relation predicts the existence of black holes with masses of 104 to 106 solar masses in low-luminosity galaxies.

However it is not clear how such a black hole would form. On the one hand, they are too massive to be formed by the collapse of a single star, which is how the stellar black holes are thought to form. On the other hand, their environments lack the extreme conditions—i.e., high density and velocities observed at the centers of galaxies—which seemingly lead to the formation of supermassive black holes. There are two popular formation scenarios for IMBHs. The first, is the merging of stellar mass black holes and other compact objects by means of gravitational radiation. The second one is the runaway collision of massive stars in dense stellar clusters and the collapse of the collision product into an IMBH.

In November 2004 a team of astronomers reported the discovery of GCIRS 13E, the first intermediate-mass black hole in our galaxy, orbiting three light-years from Sagittarius A*. [ [ S2 and Central Black Hole] ] This medium black hole of 1,300 solar masses is within a cluster of seven stars, possibly the remnant of a massive star cluster that has been stripped down by the Galactic Centre. This observation may add support to the idea that supermassive black holes grow by absorbing nearby smaller black holes and stars. However, recently, a German research group claimed that the presence of an IMBH near the galactic center is doubtful. [cite journal| id=arxiv|astro-ph|0504474 | title= A Black Hole in the Galactic Center Complex IRS 13E?| first= R.| last= Schoedel| coauthors= A. Eckart, C. Iserlohe, R. Genzel, T. Ott| journal= Astrophys. J.| volume= 625| year=2005| pages= L111–L114 | doi= 10.1086/431307] This conclusion is based on a dynamical study of a small star cluster in which should reside the suspected intermediate mass black hole. The debate on the real existence of intermediate mass black holes is still open.

More recently, in January 2006 a team led by Prof. Philip Kaaret of the University of Iowa, Iowa City announced the discovery of a quasiperiodic oscillation from an intermediate-mass black hole candidate located using NASA's Rossi X-ray Timing Explorer. The candidate, M82 X-1, is orbited by a red giant star that is shedding its atmosphere into the black hole. [ [ Dying Star Reveals More Evidence for New Kind of Black Hole | Science Blog ] ] Neither the existence of the oscillation nor its interpretation as the orbital period of the system are fully accepted by the rest of the scientific community. While the interpretation is quite reasonable, the periodicity is claimed based on only about 4 cycles, meaning that it is quite possible for this to be random variation. If the period is real, it could be either the orbital period, as suggested, or a super-orbital period in the accretion disk, as is seen in many other systems.

See also


External links

* [ Chandra images of starburst galaxy M82]
* [ NASA press release for discovery of IMBHs by] Hubble Space Telescope
* A New Breed of Black Holes, by Davide Castelvecchi Sky & Telescope April 2006

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Black hole — For other uses, see Black hole (disambiguation). Simulated view of a black hole (center) in front of the Large Magellanic Cloud. Note the gravitat …   Wikipedia

  • Intermediate-mass X-ray binary — An intermediate mass X ray binary (IMXB) is a binary star system where one of the components is a neutron star or a black hole. The other component is an intermediate mass also* X ray binary * Low mass X ray binary * High mass X ray… …   Wikipedia

  • Stellar black hole — A stellar black hole is a black hole formed by the gravitational collapse of a massive star (20 or more solar masses, though the exact amount of mass needed has not been determined and may depend on many parameters) at the end of its lifetime.… …   Wikipedia

  • Micro black hole — MBH redirects here. For other uses see MBH (disambiguation) Micro black holes are tiny black holes, also called quantum mechanical black holes or mini black holes, for which quantum mechanical effects play an important role.[1] It is possible… …   Wikipedia

  • Charged black hole — A charged black hole is a black hole that possesses electric charge. Since the electromagnetic repulsion in compressing an electrically charged mass is dramatically greater than the gravitational attraction (by about 40 orders of magnitude), it… …   Wikipedia

  • Nonsingular black hole models — A nonsingular black hole model is a mathematical theory of black holes that avoids certain theoretical problems with the standard black hole model, including information loss and the unobservable nature of the black hole event horizon. Contents 1 …   Wikipedia

  • Properties and features of black holes — According to the No Hair theorem a black hole has only three independent physical properties: mass, charge and angular momentum. [citation|last=Heusler |first=M. |year=1998 |title=Stationary Black Holes: Uniqueness and Beyond |journal=Living Rev …   Wikipedia

  • Formation and evolution of black holes — From the exotic nature of black holes, it is natural to question if such bizarre objects could actually exist in nature or that they are merely pathological solutions to Einstein s equations. However in 1970, Hawking and Penrose proved the… …   Wikipedia

  • IMBH — Intermediate Mass Black Hole Contributor: CASI …   NASA Acronyms

  • Globular cluster — s from the Sun and contains hundreds of thousands of stars. [cite news coauthors =The Hubble Heritage team url = title = Hubble Images a Swarm of Ancient Stars work = HubbleSite… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.