Supermassive black holes tend to sit, more or less stationary, at the centers of galaxies. But not all of these awesome cosmic objects stay put; some may be knocked askew, wobbling around galaxies like cosmic nomads.
We call such black holes 'wanderers', and they're largely theoretical, because they are difficult (but not impossible) to observe, and therefore quantify. But a new set of simulations has allowed a team of scientists to work out how many wanderers there should be, and whereabouts - which in turn could help us identify them out there in the Universe.
This could have important implications for our understanding of how supermassive black holes - monsters millions to billions of times the mass of our Sun - form and grow, a process that is shrouded in mystery.
Cosmologists think that supermassive black holes (SMBHs) reside at the nuclei of all - or at least most - galaxies in the Universe. These objects' masses are usually roughly proportional to the mass of the central galactic bulge around them, which suggests that the evolution of the black hole and its galaxy are somehow linked.
But the formation pathways of supermassive black holes are unclear. We know that stellar-mass black holes form from the core collapse of massive stars, but that mechanism doesn't work for black holes over about 55 times the mass of the Sun.
Astronomers think that SMBHs grow via the accretion of stars and gas and dust, and mergers with other black holes (very chunky ones at nuclei of other galaxies, when those galaxies collide).
But cosmological timescales are very different from our human timescales, and the process of two galaxies colliding can take a very long time. This makes the potential window for the merger to be disrupted quite large, and the process could be delayed or even prevented entirely, resulting in these black hole 'wanderers'. READ MORE
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