Astronomers discover a pair of twin black holes

March 5th, 2009 - 3:59 pm ICT by ANI  

Washington, March 5 (ANI): Astronomers from the National Optical Astronomy Observatory (NOAO) in Tucson, Arizona, have found what looks like a pair of twin black holes, orbiting each other in the center of one galaxy.

It has been postulated that twin black holes might exist, but it took an innovative, systematic search to find such a rare pair.

The newly identified black holes appear to be separated by only 1/10 of a parsec (1/3 of a light-year) - a tenth of the distance from Earth to the nearest star (other than the Sun).

This discovery of the most plausible binary black hole candidate ever found may lead to a greater understanding of how massive black holes form and evolve at the centers of galaxies.

After a galaxy forms it is likely that a massive black hole can also form at its center. Since many galaxies are found in clusters of galaxies, individual galaxies can collide with each other as they orbit in the cluster.

The mystery is what happens to these central black holes when galaxies collide and ultimately merge together.

Theory predicts that they will orbit each other and eventually merge into an even larger black hole.

The signature of a black hole in a galaxy has been known for many years. The material falling into a black hole emits light in narrow wavelength regions forming emission lines which can be seen when the light is dispersed into a spectrum.

These emission lines carry the information about the speed and direction of the black hole and the material falling into it.

If two black holes are present, they would orbit each other before merging and would have a characteristic dual signature in their emission lines.

This signature has now been found.

Former NOAO Director Todd Boroson and NOAO Astronomer Tod Lauer used data from the Sloan Digital Sky Survey, made with a 2.5-meter diameter telescope at Apache Point in southern New Mexico, to look for this characteristic dual black hole signature among 17,500 quasars discovered by the survey.

Boroson and Lauer had to especially careful to eliminate the possibility that they were seeing two galaxies, each with its own black hole, superimposed on each other.

To try to eliminate this superposition possibility, they determined that the quasars were at the same redshift-determined distance and that there was a signature of only one host galaxy.

The smaller black hole has a mass 20 million times that of the Sun; the larger one is 50 times bigger, as determined by the their orbital velocities. (ANI)

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