Astronomers have been solving the mysteries of quasars for 60 years


April 26, 2023

(Nanowerk News) First discovered 60 years ago, quasars can shine as bright as a trillion stars packed into a volume the size of our Solar System. In the decades since they were first observed, it has remained a mystery what could have sparked such intense activity.

New work led by scientists at the Universities of Sheffield and Hertfordshire has now revealed that it was a consequence of galactic collisions (Monthly Notices of the Royal Astronomical Society, “Galactic interaction is the dominant driver for local type 2 quasars”). Rendering of quasar P172+18 by artist Rendering of quasar P172+18 by an artist. (Image: ESO-M Kornmesser)

The collision was discovered when researchers, using deep imaging observations from the Isaac Newton Telescope in La Palma, observed the presence of distorted structures in the outer regions of galaxies that are home to quasars.

Most galaxies have a supermassive black hole at their center. They also contain large amounts of gas – but most of the time this gas orbits at great distances from the galactic center, beyond the reach of the black hole. Collisions between galaxies push gas towards the black hole at the center of the galaxy; just before the gas is consumed by the black hole, it releases tremendous amounts of energy in the form of radiation, producing the characteristic brilliance of a quasar.

Ignition of a quasar can have dramatic consequences for the entire galaxy – it can push remaining gas out of the galaxy, preventing it from forming new stars for billions of years to come.

This is the first time a quasar sample of this size has been imaged with this level of sensitivity. By comparing observations of 48 quasars and their host galaxies with images of more than 100 non-quasar galaxies, the researchers concluded that galaxies housing quasars are roughly three times more likely to interact or collide with other galaxies.

This study has provided a significant step forward in our understanding of how these powerful objects are triggered and triggered.

Professor Clive Tadhunter, from the University of Sheffield’s Department of Physics and Astronomy, said: “Quasars are among the most extreme phenomena in the Universe, and what we are seeing likely represents the future of our Milky Way galaxy when it collides with the Andromeda galaxy in about five billion years. .

“It’s great to observe these events and finally understand why they happened – but luckily Earth won’t be anywhere near one of these apocalyptic episodes for quite some time.”

Quasars are important to astrophysicists because, because of their brilliance, they stand out at great distances and therefore act as beacons to the earliest epochs in the history of the Universe.

Dr Jonny Pierce, Post-Doctoral Research Fellow at the University of Hertfordshire, explained: “This is an area that scientists around the world are eager to learn more about – one of the main scientific motivations for NASA’s James Webb Space Telescope is to study the earliest galaxies. in the Universe, and Webb is able to detect light from even the most distant quasars, emitted nearly 13 billion years ago. Quasars play a key role in our understanding of the history of the universe, and possibly the future of the Milky Way.”


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