Lesson 27 - Lecture 2 - Supermassive Black Holes.pdf - What...

Introduction to Astronomy
What Powers an AGN?
Supermassive Black Holes
Presented by Robert Wagner
• The emit jets of material in a narrow beam at speeds near the speed of light
•
This much energy, emitted from such a small region needs an energy source
much more powerful than nuclear fusion
• Quasars were much more common in the early history of the universe than
they are today
Observational Evidence for Supermassive Black
Holes
Image Credit: By Cmglee [CC BY-SA 3.0 () or GFDL ()], from
Wikimedia Commons
• Indirect evidence
• Large mass in a small volume
•
Short time period variations in brightness
•
How to determine mass?
• Kepler’s third law
• Orbits of stars near the galactic center (Milky Way):
•
Central mass must be 4.1 million M
☉
• Size is about the diameter of the orbit of Neptune
• Motions of gas in M87 (elliptical galaxy)