And while black holes<\/a> have a name for being cosmic vacuum cleaners, sucking up everything that comes in their path, this is not strictly true.<\/span><\/p>\n Black holes can actually accrete material from their near surroundings, usually gas or dust.<\/span><\/p>\n In some cases, the powerful gravitational forces involved serve to heat up this material, resulting in intense radiation being emitted.<\/span><\/p>\n These extreme objects are known as active galactic nuclei, and quasars<\/a> are the brightest and most powerful examples of them.<\/span><\/p>\n But what powers quasars?<\/p>\n Astronomers are still unsure, but Dr Jonathon Pierce, a researcher at the University of Hertfordshire<\/a> who specialises in galactic mergers, active galactic nuclei and radio astronomy<\/a>, believes merging galaxies could be the answer.<\/p>\n We spoke to Dr Pierce to find out more.<\/p>\n Supermassive black holes are roughly the size of a solar system. This is very small relative to a full galaxy<\/a>, which could contain hundreds of millions to trillions of stars.<\/p>\n There\u2019s lots of gas in galaxies, but the mystery lies in how this can get down to the central black hole regions to provide fuel for a quasar.<\/p>\n One of the leading ideas is that when galaxies collide, the net effect is to throw a large amount of material towards the galactic centres, an attractive means of getting fuel to the black hole.<\/p>\n Quasars and active galactic nuclei can emit across the full electromagnetic spectrum<\/a>, from X-rays or gamma rays all the way to radio waves, so there are many ways to study them.<\/p>\n We have amazing telescopes operating at different wavelengths.<\/p>\n There are two main approaches: you can look at triggering \u2013 what sets off or ignites a quasar \u2013 or you can look at the effects caused by feedback, where the energy output from the quasar impacts gas and dust within the galaxy.<\/p>\n We focused on triggering, and particularly on galaxy mergers.<\/p>\n We imaged a large sample of quasar-hosting galaxies with enough sensitivity to pick up on faint, distorted structures that indicate whether a galaxy is or has been going through a merger.<\/p>\n We also looked at a group of non-quasar galaxies imaged in the same way; these galaxies otherwise had very similar physical properties.<\/p>\n When we looked at the two groups, we saw that the quasar group showed signatures of mergers around three times more often than the non-quasar group.<\/p>\n This provides strong evidence that mergers are important for triggering quasars.<\/p>\n The merging galaxy theory is the most popular, but the problem has been finding evidence.<\/span><\/p>\n Even within our sample, not every quasar galaxy had signs of mergers, so there\u2019s got to be something else that can cause quasar activity.<\/span><\/p>\n One theory is that gravitational structures within spiral galaxies (spiral arms or bars, for example) could channel gas towards the centre.<\/span><\/p>\n There is also the idea that in the early Universe, at larger distances away from us, there may have been giant gas clouds within galaxies that could have collided and thrown material towards galaxy cores.\u00a0<\/span><\/p>\n Quasars are the most powerful objects in the Universe, so they\u2019re extremely interesting.<\/p>\n The sheer amount of energy output by quasars can greatly disturb the gas in a galaxy and so its ability to form new stars.<\/p>\n We want to understand what happens throughout a galactic life cycle, and this effect means that quasars could influence their evolution.<\/p>\n Quasars can also be detected at large distances because they can emit light at a comparable level to a whole galaxy.<\/p>\n![\""Artist\u2019s\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2022\/05\/eso1122a-7edd87f-e1680768367859.jpeg?quality=90&resize=620%2C368"\" "\\"\"Artist\u2019s\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>![\""jonathon\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2023\/06\/jonathon-pierce-hertfordshire-41ef0b6.jpg?quality=90&resize=620%2C516"\" "\\"\"jonathon\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>\nWhat makes quasars such mysterious objects?<\/b><\/h3>\n
How do astronomers study quasars?<\/b><\/h3>\n
![\""A\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2023\/04\/DUAL-QUASAR-J07492255-ce8d700.png?quality=90&resize=620%2C620"\" "\\"\"A\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>What approach did your team use?<\/b><\/h3>\n
What are some other theories of quasar formation?<\/b><\/h3>\n
![\""Montage\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2019\/05\/image_4568_2e-Hubble-Constant-d20468f.jpg?quality=90&resize=620%2C350"\" "\\"\"Montage\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>What do quasars tell us about the Universe?<\/b><\/h3>\n