'Spewing' black holes can prevent the births of stars

The most massive and powerful black holes prevent the birth of stars in their galaxy, researchers say.
This modified image shows the local galaxy Arp 220, as captured by the Hubble Space Telescope, with an overlaid artist's impression of jets emanating from it, indicating that the central black hole's activity is intensifying. (JPL-Caltech/NASA)

The most massive and powerful black holes prevent the birth of stars in their galaxy, researchers have learned.

Black holes, regions of space that can weigh millions or billions times more than the sun, are believed to be found at the centre of all galaxies, including our own Milky Way. 

Black holes

Einstein's general theory of relativity predicts that a black hole can form when a very large star runs out of nuclear fuel and is crushed by its own gravitational force. That force is so strong that the star collapses into a point called a singularity that is smaller than an atom's core. Its powerful gravity attracts and pulls in nearby matter and even light, making it "black."

Though the hole itself cannot be seen, it does bend light travelling past the object, causing lens-like distortions of objects behind it when looked at by distant observers such as humans on Earth.

Their location also becomes more apparent when gas is drawn into them, as when a NASA satellite recently saw the luminous flare of radiation caused by a black hole consuming a star.

Larger galaxies tend to have more massive black holes, but scientists using the European Space Agency's Herschel Space Observatory have found that galaxies with particularly active, massive black holes produce fewer stars. The research, led by Dr. Mat Page of University College London, was published in Thursday's edition of the journal Nature.

While it's easy to imagine a black hole killing stars by eating them whole, the researchers say it's actually has more to do with what the black holes are spitting out.

Contrary to the popular image, black holes do not immediately consume objects in their entirety. Some of the material is drawn into the black hole, while some is shot into space.

Gas falling into black holes releases huge amounts of energy — for instance, a star's death by black hole captured by a NASA satellite in 2010 packed a punch similar to a supernova.

"Astronomers think that if an active black hole flares up too much, it starts spewing radiation that prevents raw material from coalescing into new stars," NASA said on its website.

However, scientists still don't understand the exact connection between black holes and star formation.

"We want to know more about how this process works," Bill Danchi, a Herschel program scientist, told the NASA site. "Does star formation get disrupted from the beginning with the formation of the brightest galaxies of this type, or do all active black holes eventually shut off star formation, and energetic ones do this more quickly than less active ones?"