Starts With A Bang

Ask Ethan: How Do Black Hole Jets Carve Out Bubbles In Space? (Synopsis)

Large scale projection through the Illustris volume at z=0, centered on the most massive cluster, 15 Mpc/h deep. Shows dark matter density overlaid with the gas velocity field. Image credit: Illustris Collaboration / Illustris Simulation, via

“When a person starts to talk about their dreams, it’s as if something bubbles up from within. Their eyes brighten, their face glows, and you can feel the excitement in their words.” -John C. Maxwell

One of the most remarkable features of a great number of giant, active galaxies are the presence of jets of hyper-accelerated matter, spanning thousands of light years. Correlated with feeding, supermassive black holes are these huge structures of light-emitting matter, identifiable from many millions of light years away.

The giant elliptical galaxy, M87, and its 5,000+ light year-long jet, highly collimated, as imaged by the Hubble Space Telescope. Image credit: NASA and The Hubble Heritage Team (STScI/AURA).

Yet our best simulations show that the gas temperature rises around them not in jet-like streams, but rather in spherical explosions around these supermassive black holes. Is there an incredible disconnect between the two pictures? There might have been if you had asked only 15 years ago, but the physics of radiative feedback has evolved tremendously thanks to advances in numerical simulations, allowing us to explain this phenomenon after all.

Messier 87 in X-ray and radio. Image credit: X-ray: NASA/CXC/KIPAC/N. Werner et al Radio: NSF/NRAO/AUI/W. Cotton.

Go get the answer to Robert Coolman’s difficult question on this edition of Ask Ethan!