Astronomers Rethink Black Hole Growth Rate
February 12, 2013

Are Black Holes Growing Faster Than Previously Thought?

Lee Rannals for — Your Universe Online

The rapidly expanding problem of obesity doesn't seem to just be limited to here on Earth, because new research published in the Astrophysical Journal suggests black holes are growing at larger rates than what had previously been thought possible

Most galaxies have black holes at the center of them that can weigh anywhere from one million to one billion times as much as the Sun. The black hole found in the middle of our Milky Way Galaxy has been consuming the equivalent of one Sun every 3,000 years.

Astronomers previously thought black holes grow mostly when galaxies crash into one another, during which, a large concentration of gas begins to form around the black hole, creating the active galactic nucleus. This gas gets so bright active galactic nuclei can be seen all the way back to just after the universe formed. Under this theory, black holes found in the center of galaxies experience limited growth potential. However, the latest study challenges this thought.

The team was able to disprove the previous theory, stating black holes are unable to grow, by using computer simulations to compare the masses of black holes in spiral galaxies with those of elliptical galaxies. They compared spiral and elliptical galaxies, finding there is not a mismatch between how big their black holes are.

Observations by the Hubble Space Telescope indicated black holes can grow even in quiet spiral galaxies. A gas cloud recently found near the center of the Milky Way will be ripped apart by the central black hole later this year. Over the next 10 years, the black hole is predicted to swallow up as much as 15 times the mass of the Earth from this cloy.

Researchers used the property of black holes first discovered by Hubble for the study, which says their masses can accurately be predicted from the speed of stars in the galaxies in which they reside.

The black hole located in the Sombrero Galaxy has grown the most. Researchers believe this black hole has been swallowing the equivalent of one Sun every twenty years, and is now over 500 million times as heavy as the Sun.

The latest study provides the theoretical basis for understanding the emerging picture that galaxy collisions are a relatively small contribution to the growth of black holes.

“These simulations show that it is no longer possible to argue that black holes in spiral galaxies do not grow efficiently. Our simulations will allow us to refine our understanding of how black holes grew in different types of galaxies.” Dr. Victor Debattista, the University of Central Lancashire astronomer who led the study, said in a statement.

Recently, redOrbit also reported about a new method to find and study supermassive black holes at the cores of galaxies. This new method could one day allow scientists to better explain the mysterious objects, expanding the inventory of supermassive black holes. With this expansion of data, it will open up knowledge about how these mysterious objects formed, evolve and interact with the galaxies they exist within.