AST201H1 Lecture Notes - Lecture 6: Cygnus X-1, Event Horizon, Radiography

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST201H1
• Professor: Michael Reid

Document Summary

In 1973, astronomers (including some at uoft) discovered a star orbiting something small and dark which was 15 times the mass of the sun. Later observations showed that the small dark thing was much smaller than the sun and it was producing a lot of x-rays. The x-rays we see coming from cygnus x-1 were emitted by hot material just outside the event horizon. Cygnus x-1 is about 15 times the mass of the sun, so its schwarzschild radius is only about 44km. Cygnus x-1 is a stellar-mass black hole. Stellar-mass black holes form when very large stars die in supernova explosions. Every galaxy probably has thousands or millions of stellar-mass black holes. A much larger kind of black hole, found only at the centers of galaxies, called. Evidence of the supermassive black hole: the motions of the gas and stars at the center indicate that it contains a million solar masses within a region only about 1 parsec across.