PARIS, April 26, 2023 (BSS/AFP) - Astronomers said Wednesday that for the 
first time they have confirmed what ignites quasars, the brightest and most 
powerful objects in the universe, which put galaxies in their "death throes".

These celestial behemoths form when two galaxies smash into each other, the 
astronomers said, warning that this could be the Milky Way's fate in a few 
billion years.

Quasars are one of the most extreme objects in the universe, some shining 
with the brightness of a trillion stars despite being packed into the space 
of our Solar System.

They sit in the heart of galaxies, powered by supermassive black holes, 
requiring a huge amount of gas to be so staggeringly bright.

But exactly what creates quasars has been a matter of debate since their 
discovery in the 1950s.

In a new study, an international team of researchers said they have "clear 
evidence" that quasars are triggered by two galaxies colliding, which 
releases the vast amounts of energy needed.

Clive Tadhunter, an astrophysicist at the University of Sheffield in the UK 
and one of the study's authors, told AFP that this could be the fate of the 
Milky Way one day.

The nearby Andromeda Galaxy is "coming directly towards us at about 200 
kilometres (125 miles) a second," he said.

It will collide with the Milky War in roughly five billion years, and "we 
could get a quasar" as a result, he said.

Quasars push out all the gas from a galaxy, preventing any new stars from 
forming, he added.

- 'Beacons to the distant universe' - 

The researchers compared observations of 48 galaxies with quasars at their 
centre to 100 without them.

Galaxies hosting quasars were three times as likely to have had collisions 
with other galaxies, the study said.

While the theory that such collisions ignited quasars has been around for 
decades, it was difficult to prove. 

Tadhunter said this was because observations had often been carried out with 
telescopes that were optimised to look at objects in the centre of galaxies, 
but were less effective at spotting the distorted features at their edges 
that indicate past collisions.

For example, these diffuse structures "get washed out" when observed by the 
Hubble Space Telescope, he said.

So the team used land-based observatories, such as the Isaac Newton Telescope 
on the Spanish island of La Palma.

The new study, published in the Monthly Notices of the Royal Astronomical 
Society, also reviewed previous research to show how it may have missed the 
tell-tale signs of collisions.

Tadhunter said that quasars "act like beacons to the distant universe" 
because of their incredible brightness.

The James Webb Space Telescope, which has a much bigger aperture than Hubble, 
could help reveal more about quasars in this distant universe, when the 
universe was in its infancy, he said.