60 years after their discovery, the mystery of the origin of quasars has finally been solved, objects that can shine with the same brightness as a trillion stars enclosed in a volume the size of our Solar System: the phenomenon is triggered by collisions between galaxies that host supermassive black holes, a process that releases extraordinary amounts of energy. The confirmation comes from a study published in the journal Monthly Notices of the Royal Astronomical Society and led by the British University of Hertfordshire, which also allows us to take a look at the future of the Milky Way: our galaxy, in fact, will experience its own quasar between about 5 billion years, when it will collide with its neighbor, the Andromeda galaxy.
Quasars are fundamental for astrophysicists because, thanks to their incredible luminosity, they can also be observed at very great distances and therefore act as beacons for the first epoch of the universe. Researchers led by Jonny Pierce studied 48 galaxies that host quasars and compared them with 100 others in which these objects are absent. Their violent origin was discovered when the authors of the study, using data from the Isaac Newton telescope on the island of La Palma in the Canary Islands, observed the presence of distorted structures in the outer regions of the galaxies that host the quasars.
Most galaxies (including ours) have a supermassive black hole at their center. When two galaxies collide, the gas present is pushed towards these voracious objects: however, just before the gas is consumed, it releases enormous amounts of energy in the form of radiation, giving rise to the characteristic brightness of quasars. The ignition of these phenomena can have dramatic consequences for the galaxies that host them: the rest of the gas could be expelled from the galaxy, preventing it from forming new stars for billions of years.
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