'Smallest Supermassive Black Hole Ever Detected'

Astronomers using Nasa's Chandra X-ray Observatory and the 6.5-metre Clay Telescope in Chile have identified the smallest supermassive black hole ever detected in the centre of a galaxy.

This "oxymoronic" object could provide clues to how larger black holes formed along with their host galaxies 13 billion years or more in the past.

Astronomers estimate this supermassive black hole is about 50,000 times the mass of the sun.

This is less than half the mass of the previous smallest black hole at the centre of a galaxy.

"It might sound contradictory, but finding such a small, large black hole is very important," said Vivienne Baldassare from the University of Michigan in Ann Arbor in a statement.

"We can use observations of the lightest supermassive black holes to better understand how black holes of different sizes grow," he added in a paper which appeared in the Astrophysical Journal Letters.

The tiny heavyweight black hole is in the centre of a dwarf disk galaxy called RGG 118, located about 340 million light years from Earth.

Researchers used the Chandra data to figure out the X-ray brightness of hot gas swirling toward the black hole.

They found the outward push of radiation pressure of this hot gas is about one percent of the black hole's inward pull of gravity, matching the properties of other supermassive black holes.

The black hole in RGG 118 is nearly 100 times less massive than the supermassive black hole found in the centre of the Milky Way.

It's also about 200,000 times less massive than the heaviest black holes found in the centres of other galaxies.

Astronomers are trying to understand the formation of billion-solar-mass black holes from less than a billion years after the big bang, but many are undetectable with current technology.

The black hole in RGG 118 gives astronomers an opportunity to study a nearby small supermassive black hole.