Rapidly growing black hole may provide clues to evolution of galaxies

Houston, February 25

Astronomers have discovered a rapidly growing black hole in one of the most extreme galaxies known in the very early Universe, according to a new study.

The discovery of the galaxy and the black hole at its centre provided new clues on the formation of the very first supermassive black holes, the researchers from the University of Texas, US, and the University of Arizona, US, said.

Using observations taken with the Atacama Large Millimeter Array (ALMA), a radio observatory sited in Chile, the team have determined that the galaxy, named COS-87259, containing this new supermassive black hole is very extreme, forming stars at a rate 1000 times that of our own Milky Way and containing over a billion solar masses worth of interstellar dust, the study said.

The galaxy shines bright from both this intense burst of star formation and the growing supermassive black hole at its centre, the study reportedly said.

The new work is published in the journal Monthly Notices of the Royal Astronomical Society.

The black hole is considered to be a new type of primordial black hole – one heavily enshrouded by cosmic “dust”, causing nearly all of its light to be emitted in the mid-infrared range of the electromagnetic spectrum, the researchers said.

They have also found that this growing supermassive black hole, frequently referred to as an active galactic nucleus, is generating a strong jet of material moving at near light speed through the host galaxy.

Today, black holes with masses millions to billions of times greater than that of our own Sun sit at the centre of nearly every galaxy.

How these supermassive black holes were first formed remains a mystery till date for the scientists, particularly because several of these objects have been found when the Universe was still very young.

Because the light from these sources takes so long to reach us, we see them as they existed in the past; in this case, just 750 million years after the Big Bang, which is approximately 5 per cent of the current age of the Universe.

In this study, what is particularly astonishing about this new object is that it was identified over a relatively small patch of the sky typically used to detect similar objects — reportedly less than 10 times the size of the full moon — suggesting there could be thousands of similar such sources in the very early Universe.

This was completely unexpected from previous data, the study said.

The only other class of supermassive black holes we knew about in the very early Universe are quasars, which are active black holes that are relatively unobscured by cosmic dust.