Black holes are some of the most mysterious objects in our universe — but are they also among the most necessary?

Image: Artist's concept of a growing black hole at the center of a faraway galaxy. (NASA/JPL-Caltech)

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Astrophysicist James Geach stopped by today to answer our questions about the formation and evolution of galaxies, including this one on whether a central black was necessary in order to form a galaxy. While it may not be required to form a galaxy, Geach explains, it may be necessary to let that galaxy evolve:

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Is a central black hole required for galaxy formation?

James Geach

It might not be required to actually *form* a galaxy, but the presence of a central black hole appears to be very important for the evolution of galaxies: there is a strong correlation between the mass of the central black hole and the mass of stars in the bulge surrounding it, despite many orders of magnitude difference in physical scale. We think that the growth of the stars and black hole are linked via a process called feedback, where energy released during the growth of the BH, called an active galactic nucleus (AGN) regulates the formation of stars. This is a hot topic of research right now.

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You can read Geach's full Q&A — where he explains the mechanics of galaxy collision and also offers tips on just where in the solar system you might head for the best possible star-gazing — right here.