Galactic Bubbles

The supermassive black hole at the center of the Milky Way galaxy is surrounded by millions of stars and by giant clouds of gas — material that should serve up a feast for the black hole. Yet for the most part, the black hole appears to be on a starvation diet. It occasionally ingests a few wisps of gas or a clump the size of an asteroid, but otherwise it’s quiet.

The black hole may be deprived of the rich buffet around it by the actions of the stars themselves. They may direct much of the gas away from the black hole and into intergalactic space.

The black hole’s gravity pulls in vast clouds of gas. But very little of the gas pours into the black hole itself. Instead, the clouds appear to slam together and break into smaller clumps, which collapse to form stars.

Radiation from the newborn stars, as well as the explosions of massive stars, blows away much of the remaining gas. The radiation also gives an electric charge to much of the gas, which is then funneled away by the vast mag