Washington: A team of astronomers has announced that they have discovered 33 pairs of waltzing black holes in distant galaxies.
Dr. Julia Comerford of the University of California, Berkeley, US, made the announcement.
Astronomical observations have shown that nearly every galaxy has a central supermassive black hole (with a mass of a million to a billion times the mass of the Sun), and galaxies commonly collide and merge to form new, more massive galaxies.
As a consequence of these two observations, a merger between two galaxies should bring two supermassive black holes to the new, more massive galaxy formed from the merger.
The two black holes gradually in-spiral toward the center of this galaxy, engaging in a gravitational tug-of-war with the surrounding stars.
The result is a black hole dance.
Such a dance is expected to occur in our own Milky Way Galaxy in about 3 billion years, when it collides with the Andromeda Galaxy.
Astronomers expect there to be many such waltzing supermassive black holes in the Universe, but until recently only a handful had been found.
Dr. Comerford and her colleagues announce the discoveries of 33 new pairs of waltzing supermassive black holes, which help alleviate the discrepancy between the expected and observed numbers of black hole pairs.
Dr. Comerford and her colleagues observed the waltzing black holes that have gas collapsing onto them, and this gas releases energy and powers each black hole as an active galactic nucleus (AGN).
Using the techniques of searching for waltzing supermassive black holes by their velocities and obtaining spectra of galaxies that show two bright central nuclei and evidence of recent galaxy mergers, Dr. Comerford and her colleagues discovered a total of 33 pairs of supermassive black holes in distant galaxies.
These discoveries are significant because “they show that dual supermassive black hole systems are much more common than previously known from observations,” said Dr. Comerford.
The dual supermassive black hole pairs can in turn be used to estimate how often galaxies merge, and the team concludes that red galaxies from between 4 and 7 billion years ago underwent 3 mergers every billion years.
First Published: Tuesday, January 05, 2010, 14:11