Washington, There are limits to how big super gigantic black holes can grow, according to the latest research led by an Indian-American astrophysicist of Yale University.

These "ultra-massive" black holes have been shown to have masses upwards of one billion times that of our own Sun, which is where they have set the limit on themselves.

Priyamvada Natarajan, associate professor of astronomy at Yale and Ezequiel Treister, a postdoctoral fellow at Hawaii University, have shown that even the biggest of these gravitational monsters can't keep growing forever.

Instead, they appear to curb their own growth - once they accumulate about 10 billion times the mass of the Sun.

These black holes, found at the centres of giant elliptical galaxies in huge galaxy clusters, are the biggest in the known universe.

Even the large black hole at the centre of our own Milky Way galaxy is thousands of times smaller these behemoths. But these gigantic black holes, which accumulate mass by sucking in matter from neighbouring gas, dust and stars, seem unable to grow beyond this limit regardless of where - and when - they appear in the universe.

"It's not just happening today," said Natarajan. "They shut off at every epoch in the universe."

Natarajan and Treister used existing optical and X-ray data of these ultra-massive black holes to show that, in order for those various observations to be consistent, the black holes must essentially shut off at some point in their evolution.

One possible explanation put forth by Natarajan is that the black holes eventually reach the point when they radiate so much energy as they consume their surroundings that they end up interfering with the very gas supply that feeds them, which may interrupt nearby star formation.

"Evidence has been mounting for the key role that black holes play in the process of galaxy formation," said Natarajan. "But it now appears that they are likely the prima donnas of this space opera."

These findings will appear in the Monthly Notices of the Royal Astronomical Society (MNRAS).

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