Black holes can create jets that control galaxy evolution

Scientists suggest that the jets that control galaxy evolution might be formed by retrograde spin of supermassive black holes.

Updated: Feb 12, 2010, 13:32 PM IST

Washington: A team of scientists has suggested that the jets that control galaxy evolution might be formed by the retrograde spin of supermassive black holes.
Every galaxy has a collection of black holes, regions that gobble up matter and energy and can each be up to 10 times the Sun’s mass.

In addition to these black holes, there is a supermassive black hole embedded in the heart of each galaxy that is roughly one million to one billion times the mass of the Sun.

About 10 percent of these giant black holes feature jets of plasma, or highly ionized gas, that extend in opposite directions.

By spewing huge amounts of mostly kinetic energy, or energy created by motion, from the black holes into the universe, the jets control how stars and other bodies form, and play a crucial role in the evolution of clusters of galaxies, the largest structures in the universe.

How the jets form remains one of the most important unsolved mysteries in extragalactic astrophysics, and Dan Evans, a postdoctoral researcher from MIT’s Kavli Institute for Astrophysics and Space Research (MKI), may be one step closer to unlocking that mystery.

For two years, Evans has been comparing several dozen galaxies whose black holes host powerful jets to those galaxies with supermassive black holes that do not eject jets.

All black holes - those with and without jets - feature accretion disks, the clumps of dust and gas rotating just outside the event horizon.

By examining the light reflected in the accretion disk of an AGN black hole, Evans concluded that jets may form right outside black holes that have a retrograde spin, or that are spinning in the opposite direction from their accretion disk.