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Astronomers Solve the 60-Year Mystery of Quasars – the Most Powerful Objects in the Universe
Scientists have unlocked one of the biggest mysteries of quasars by discovering that they are ignited by galaxies colliding [sheffield.ac.uk]:
First discovered 60 years ago, quasars can shine as brightly 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 trigger such powerful activity. New work led by scientists at the Universities of Sheffield and Hertfordshire has now revealed that it is a consequence of galaxies crashing together.
The 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.
The study has provided a significant step forward in our understanding of how these powerful objects are triggered and fuelled.
Journal Reference:
C S Pierce et al., Galaxy interactions are the dominant trigger for local type 2 quasars [open], Monthly Notices of the Royal Astronomical Society, Volume 522, Issue 2, June 2023, Pages 1736–1751, https://doi.org/10.1093/mnras/stad455 [doi.org]
