60 years ago quasars were discovered, the most powerful and luminous star-like celestial objects found in the core of galaxies.

But until today it remained a mystery what could cause such a strong activity and answers are provided by research published in the journal “Monthly Notices of the Royal Astronomical Society”.

By observing 48 galaxies hosting quasars and comparing them to more than 100 galaxies without quasars, a scientific team led by the Universities of Sheffield and Hertfordshire discovered that the phenomenon is the result of colliding galaxies.

When two galaxies collide, the gravitational forces push huge amounts of gas towards supermassive black holes at the center of the remnant of the colliding galaxy system. Just before the gas is consumed by the black hole, it releases enormous amounts of energy in the form of radiation, and this results in the characteristic luminosity of quasars.

The researchers also concluded that galaxies with quasars are about three times more likely to interact or collide with other galaxies.

“Quasars are one of the most extreme phenomena in the Universe and what we see is likely to represent the future of our own Galaxy when it collides with the Andromeda galaxy in about five billion years,” says the professor in the University’s Department of Physics and Astronomy of Sheffield, Clive Tanthunder.

Quasars are important to astrophysicists because their brightness makes them stand out at great distances and act as beacons for the early ages of the Universe’s history.

“One of the main scientific motivations for NASA’s James Webb Space Telescope was to study the early galaxies in the Universe, and this telescope is able to detect light from even the most distant quasars, emitted nearly 13 billion years ago.” , explains postdoctoral researcher at the University of Hertfordshire, Jonny Pearce.