Black Holes: Facts, Theory, and Definition

1. Black Holes: Facts, Theory, and Definition An artist's drawing a black hole named Cygnus X-1. It formed when a large star caved in. This black hole pulls matter from blue star beside it. Image Credit:  NASA/CXC/M.Weiss

2. http://www.space.com/15421-black-holes-facts-formation-discovery-sdcmp.htmlhttp://www.space.com/15421-black-holes-facts-formation-discovery-sdcmp.html

3. What is a Black Hole? • VERY dense place in space where gravity has become so extreme that it overwhelms all other forces. • Gravity is so strong because matter has been squeezed into a tiny space. • Because no light can escape, we can't see black holes. • But…we can see how stars and gas that are very close act differently than other stars. • When a star and black hole are close together, high energy light is made and can be measured by satellites/telescopes. • May pull gas off the star and create an “accretion disk” around itself.

6. Discovery • First predicted by Einstein in 1916 with the general theory of relativity. • Term “black hole” was coined in 1967 by John Wheeler, American astronomer. • First discovered by Wheeler in 1971

7. Type: Primordial • Smallest • Scientists think they may be the size of a single atom but have the mass of a mountain • Thought to have formed early (right after the Big Bang)

8. Type: Stellar • Formed when a massive star collapses • Relatively small, but VERY dense • Mass may be up to 20x more than the mass of our Sun • Consume dust and gas around them to grown in size.

9. Type: Supermassive • May be millions or billions of times the mass of the Sun but have the same radius • Thought to be at the center of every galaxy • Sagittarius A is the center of Milky Way. • Scientists aren’t sure how they form, may be the result of: • many smaller black holes merging • large gas clouds collapsing and accreting mass • collapse of a group of stars • Once formed, they gather gas and dust from around them and grow.

10. Black Hole Theory • Incredibly massive but only cover a small area. • Extremely strong gravitational force – not even light can escape • Holes have 3 “layers” • Outer event horizon • Inner event horizon • Singularity

11. The layers… • Event horizon - boundary around the mouth of the black hole where light loses its ability to escape • Once a particle crosses the event horizon, it cannot leave. • Singularity • Single point in space-time where the mass of the black hole is concentrated.

12. Interesting facts! • If you fell into a black hole, gravity would stretch you out like spaghetti. Don't worry; your death would come before you reached singularity. • Black holes do not "suck." Suction is caused by pulling something into a vacuum, which the massive black hole definitely is not. Instead, objects fall into them. • The first object considered to be a black hole is Cygnus X-1. Rockets carrying Geiger counters discovered eight new x-ray sources. In 1971, scientists detected radio emission coming from Cygnus X-1, and a massive hidden companion was found and identified as a black hole. • Cygnus X-1 was the subject of a 1974 friendly wager between Stephen Hawking and a fellow physicist Kip Thorne, with Hawking betting that the source was not a black hole. In 1990, he conceded defeat. [VIDEO: Final Nail in Stephen Hawking's Cygnus X-1 Bet?] • Miniature black holes may have formed immediately after the Big Bang. Rapidly expanding space may have squeezed some regions into tiny, dense black holes less massive than the sun. • If a star passes too close to a black hole, it can be torn apart. • Astronomers estimate there are anywhere from 10 million to a billion stellar black holes, with masses roughly thrice that of the sun, in the Milky Way. • The interesting relationship between string theory and black holes gives rise to more types of massive giants than found under conventional classical mechanics.

13. http://www.youtube.com/watch?v=eI9CvipHl_c&feature=related http://www.youtube.com/watch?v=p2zhaoyMYGA