Monster black hole 3 billion times the mass of the sun formed by trio of colliding galaxies

Three colliding spiral galaxies 1.8 billion light years from Earth have produced a monster black hole weighing in at 3 billion times the mass of the Sun.

The surprise discovery, which was triggered by a routine testing of a new telescope, has been accepted for publication in Monthly Notices of the Royal Astronomical Society.

"The black hole at the centre of our galaxy is only 4 million solar masses, so this one is a monster in comparison," said lead author, Dr Lisa Harvey-Smith from CSIRO Astronomy and Space Science.

In 1989, the Nature journal reported an observation of gas called an astrophysical maser in the far away galaxy IRAS 20100-4156.

This galaxy is actually a trio of galaxies, which are in the process of colliding, and the black holes in their centres are merging to form a supermassive black hole.

Dr Harvey-Smith decided to measure the spectrum of radio waves emitted by the maser as part of a test observation by CSIRO's new radio telescope, the Australian Square Kilometre Array Pathfinder (ASKAP) in Murchison.

"It thought it would be quite a mundane thing," she said.

But upon further checks with the Australia Telescope Compact Array telescope at Narrabri, the researchers spotted something interesting.

Fast moving gas points to black hole mass

They found the maser was moving twice as fast as previously thought — no less than 600 kilometres a second around the centre of the galaxy.

The gas forming the maser is being swirled around by gravity from the supermassive black hole at the centre of the galaxy.

"This very fast motion of the gas tells us about how massive the black hole is," said Dr Harvey-Smith.

"The really exciting thing about this is it is a direct measurement of the mass of the black hole by stuff that's swirling around it."

The formation of super massive black holes through the merging of galaxies creates a starburst, in which stars start forming hundreds of times more quickly than they did before.

This enables astronomers to see the galaxy so many light years away.

Measuring the mass of many supermassive black holes in galaxies of different ages could give insights into how galaxies have evolved over the history of the universe, Dr Harvey-Smith said.

"We want to know whether galaxy collisions, and the formation of super massive black holes, have really driven the star formation rates that we see in galaxies and how that's changed throughout time," she said.