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Top Comments: New Study Reveals How Quasars Form. [1]

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Date: 2023-04-27  

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I was a kid at the height of NASA’s manned space flight program (I turned 10 just weeks after Apollo 11 landed on the Moon), and nothing inspired me more than learning about what was out there in space to explore. I wanted to absorb all the information I could about the planets in our solar system, about the stars and nebulas that made up our Milky Way Galaxy, about the other galaxies that lay unimaginably further away, and anything and everything else I might be able to learn about space. Sometime during the late 1960s or early 1970s, I remember reading an article about astronomical objects called quasars. The name come from shortening what these objects were called previously: quasi-stellar objects. They were first identified during the infancy of radioastronomy as sources of high-intensity radiation. Comparison of the locations of these sources to astronomical images showed that they were located in very distant galaxies (the closest one to us is 600 million light years away). The radiant power of a typical quasar is thousands of times the total power of our own galaxy, but confined to a volume no larger than our solar system. The articles I read about them quoted astronomers as being confounded about what could be producing so much radiation from such a small volume. Nowadays, the answer is pretty obvious: an enormous black hole will do that, but back in those days, the concept of a black hole had not yet entered popular discourse (at least, I never saw mention of them).

So we have a much better idea of what a quasar is, but there are lots of supermassive black holes in the universe. What causes these particular ones to pump out such huge amounts of radiation? A new study led by astronomers in Britain has yielded some clues. Apparently, quasars form as a result of collisions between galaxies.

he collisions were 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 the galaxies that are home to quasars. Most galaxies have supermassive black holes at their centres. They also contain substantial amounts of gas -- but most of the time this gas is orbiting at large distances from the galaxy centres, out of reach of the black holes. Collisions between galaxies drive the gas towards the black hole at the galaxy centre; just before the gas is consumed by the black hole, it releases extraordinary amounts of energy in the form of radiation, resulting in the characteristic quasar brilliance. … This is the first time that a sample of quasars of this size has been imaged with this level of sensitivity. By comparing observations of 48 quasars and their host galaxies with images of over 100 non-quasar galaxies, researchers concluded that galaxies hosting quasars are approximately three times as likely to be interacting or colliding with other galaxies.

So there you have it. Galactic collisions cause commonly cause the conditions for quasars to form by providing their resident black holes with the necessary fuel to pump out the enormous radiant intensities we observe.

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[1] Url: https://www.dailykos.com/stories/2023/4/27/2166319/-Top-Comments-New-Study-Reveals-How-Quasars-Form

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