Astronomers zoom in on the origin of black holes
A TEAM of astronomers at Cardiff University have observed a low-mass supermassive black hole that could be the missing link between two leading theories on how the cosmic monsters are born.
Supermassive black holes or SMBHs are the largest known type of black hole, weighing thousands or billions of times more than our Sun.
But very little is known about the colossal object and astronomers are still unsure how they are born.
According to one theory, supermassive black holes were born shortly after the Big Bang in a process dubbed a “direct collapse”.
In this scenario, extremely large supermassive black holes would have been born with a fixed minimum size and weight hundreds of thousands to millions of times than our Sun.
Another theory suggests SMBHs were born much later from “seed” black holes that formed with the dying breath of supermassive stars.
In this case, SMBHs would start out small – about 1,000 times heavier than our Sun – and feed on surrounding stars and gas to gradually grown in mass.
In a study published in Monthly Notices of the Royal Astronomical Society, the Cardiff-led team has presented evidence of a supermassive black hole less than one million times the mass of our Sun.
Astronomers have been trying to hunt these low-mass SMBHs for a long time.
The black hole sits at the centre of Mirach’s Ghost (NGC 404) – a galaxy about 10 million light-years away.
Dr Tim Davis from Cardiff University’s School of Physics and Astronomy said: “The SMBH in Mirach’s Ghost appears to have a mass within the range predicted by ‘direct collapse’ models.
“We know it is currently active and swallowing gas, so some of the more extreme ‘direct collapse’ models that only make very massive SMBHs cannot be true.
“This on its own is not enough to definitively tell the difference between the ‘seed’ picture and ‘direct collapse’ – we need to understand the statistics for that – but this is a massive step in the right direction.”
The findings were made using a new technique at the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean Andes, Chile.
The cutting-edge telescope is being used to study some of the coldest objects in the universe.
Astronomers believe nearly all large galaxies, including our own, contain a supermassive black hole in their centre.
In the case of the Milky Way, it is a supermassive black hole about 26,000 light-years away that is known as Sagittarius A*.
The astronomers used a new technique to zoom further into the centre of Mirach’s Ghost than has ever been done before.
The technique allowed the astronomers to observe the clouds of gas swirling around the black hole.
The gas clouds were found to only measure about 1.5 light-years across.
Dr Davis said: “Our study demonstrates that with this new technique we can really begin to explore both the properties and origins of these mysterious objects.
“If there is a minimum mass for a supermassive black hole, we haven’t found it.”