- Black holes with a billion times the sun’s mass already existed early in the universe. How did these behemoths grow so big, so fast? What process formed the “seed” black holes from which they grew?
- Did the death throes of the first stars provide numerous small seeds that then merged together, or did vast primordial gas clouds bypass the star stage and collapse to form larger seeds directly?
- Astronomers are trying to solve this mystery by finding and analyzing leftover seeds—“middleweight” black holes. Early indications suggest that middleweights formed by direct collapse.
Astronomers have known for some 10 years that nearly every large galaxy contains at its core an immense black hole—an object having such intense gravity that even light cannot escape. The death of stars can produce small black holes—with masses ranging from about three to 100 times the mass of the sun—but such stellar-mass black holes are tiny compared with the behemoths at the centers of galaxies, measuring millions to billions of solar masses.
These supermassive black holes pose major puzzles: Why are they so common in galaxies? Which came first—the galaxy or the hole? And how did they form in the first place?