They solve a puzzle about quasars after more than 60 years

Quasars are astronomical objects that can shine as bright as a trillion (one million million) stars, even though they are about the same size as our solar system. Until now, it was a mystery what could trigger such a colossal activity.

Research conducted from the University of Sheffield and the University of Hertfordshire, both in the United Kingdom, has now revealed what circumstances promote the formation of a quasar.

Broadly speaking, quasars are astronomical objects powered by a supermassive black hole at their center, surrounded by a very large amount of matter in the process of being swallowed. The activity of the hole sucking in matter is so frenzied that the matter heats up enormously and releases extraordinary amounts of energy in the form of radiation, giving rise to the characteristic glow of quasars.

The first clue to solving the puzzle of what circumstances promote quasar formation came when the research team, including Jonny Pierce and Clive Tadhunter, noticed the presence of distorted structures in the outer regions of galaxies. that harbor quasars. The observations that allowed the team to examine these features were made using the Isaac Newton Telescope on La Palma, one of Spain’s Canary Islands.

It is the first time that such a large sample of quasars has been obtained with this level of sensitivity.

Artist’s impression of the quasar P172+18. (Image: ESO / M. Kornmesser. CC BY 4.0)

By comparing observations of 48 quasars and their host galaxies with images of more than 100 non-quasar galaxies, the researchers concluded that galaxies hosting quasars are about three times more likely to be interacting or colliding with other galaxies, activity that causes the aforementioned distortions. This suggests that the existence of a quasar is caused by a collision between galaxies.

Most galaxies have supermassive black holes at their centers. They also contain substantial amounts of gas, but most of the time much of this gas orbits at great distances from the centers of galaxies, out of reach of black holes.

Collisions between galaxies propel gas towards a supermassive black hole in the central zone and, therefore, put a large amount of matter within its reach, thus creating the ideal scenario for the emergence of a quasar.

The start-up of a quasar can mark the future of the entire galaxy in which it nests in many aspects. It can push the rest of the gas out of the galaxy, greatly limiting the formation of new stars for billions of years. The galaxy is doomed to lack young stars and also very bright stars such as blue giants, since the only ones that can last for billions of years are of more modest brightness.

The study is titled “Galaxy interactions are the dominant trigger for local type 2 quasars”. And it has been published in the academic journal Monthly Notices of the Royal Astronomical Society. (Fountain: NCYT by Amazings)