John Kormendy: Black Holes

Where do supermassive black holes reside, and how do they influence their host galaxies?

John Kormendy searched for answers by studying the centers of some of the biggest nearby galaxies.

Supermassive black holes (SBHs) a million to a few billion times more massive than our Sun are thought to live at the centers of galaxies, including our Milky Way. How they form is a mystery.

Since they don’t emit light, they are hard to study  directly,  but their strong gravity make the stars very close to them whizz around much faster than in their absence,

In the 1980s, he used the Canada France Hawaii Telescope to study the velocities of stars near the center of galaxies and discovered SBHs with the expected masses in the nearby Andromeda galaxy, in the Sombrero galaxy, and in three other galaxies. These were some of the first directly detected SBHs.

A surprising discovery was that the large spiral galaxy M33 contained neither a supermassive black hole nor a bulge.

“For decades, astronomers studied quasars and other active galactic nuclei and concluded that their engines are supermassive black holes that produce prodigious energies when they swallow stars and gas. Hundreds of other astronomers studied galaxy structure and came to understand, in a general way, at least, how various kinds of galaxies evolved. Now the realization that supermassive black holes and galaxies sometimes but not always influence each other’s evolution has merged these two subjects into one.  This brings to mind a quote from John Muir’s My First Summer in the Sierra: “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.”     — John Kormendy