Unveiling Black Holes: Cosmic Secrets Revealed

1. BlackHoles Authors: Logan Hinds, Palmer Vazquez, Brandon Nguyen

2. Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive or larger undergoes a supernova explosion, it may leave behind a fairly massive burned out stellar remnant. With no outward forces to oppose gravitational forces, the remnant will collapse in on itself. The star eventually collapses to the point of zero volume and infinite density, creating what is known as a "singularity", or the center of a black hole. Around the singularity is a region where the force of gravity is so strong that not even light can escape. Thus, no information can reach us from this region. It is therefore called a black hole, and its surface is called the "event horizon".

3. The existence of black holes was first proposed in the 18th century, based on the laws of gravity. The more massive an object, the larger the gravitational force felt on its surface. John Michell and Pierre-Simon Laplace both independently argued that if an object were either extremely massive or extremely small, it might not be possible at all to escape its gravity. Even light could be forever captured. Black holes often look very different from each other. But this is because of variety in what happens in their surroundings.

4. The black holes themselves are all identical, except for three characteristic properties: the mass of the black hole, its spin (whether AND how fast it rotates around an axis), and its electric charge. Amazingly, black holes completely erase all of the other complex properties of the objects that they swallow. Astronomers can measure the mass of black holes by studying the material that orbits around them. So far, we have found two types of black holes: stellar-mass (just a few times heavier than our Sun) or super-massive (about as heavy as a small galaxy).

5. But black holes might exist in other mass ranges as well. For example, recent observations suggest there may be black holes with masses between stellar-mass and supermassive black holes. Black holes can spin around an axis, although the rotation speed cannot exceed some limit. Astronomers think that many black holes in the Universe probably do spin, because the objects from which black holes form generally rotate as well.

6. Observations are starting to shed some light on this issue, but no consensus has so far emerged. Black holes could also be electrically charged. However, they would then rapidly neutralize that charge by attracting and swallowing material of opposite polarity. So astronomers believe that all black holes in the Universe are uncharged.

7. Black Hole Quiz What is the surface of a black hole called? Are all black holes the same? Can light escape a black hole? What are the two types of black holes? When was the existence of a black hole proposed? A1: Event Horizon A2: No A3: No A4: Stellar-Mass & Supermassive A5: in the 18th Century

8. Credits • http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html • Project Leader: Dr. Jim LochnerCurator: Meredith GibbResponsible NASA Official: Phil Newman • http://hubblesite.org/explore_astronomy/black_holes/encyclopedia.html • Logan Hinds, Palmer Vasquez, and Brandon Nguyen