Black Holes

1. Distinguishes between an event horizon and an accretion zone of a black hole.

The accretion zone has matter that is just floating around, the event horizon is the place that if matter passes into this it will be sucked in and lost forever.

2. Defines escape velocity, black hole, and the speed of light.

Escape Velocity- The speed needed to break free from a gravitational field.
Black Hole- An area that is so compact that when you get too close, the speed of light isn't fast enough to escape.
Speed of Light- The speed of (2.99793 X 10⁸ m/s, or 186,000 miles/s). It is a constant in empty space.

3. Explains the relationship between escape velocity, black hole, and the speed of light.

The speed of light isn't fast enough to escape a black hole, which is composed of escape velocity.

4. Identifies more than one single type of black hole.

Stellar Black holes- When a massive star super novas.
Super Massive Black holes- At the center of galaxies.
Quasars- When 2 black holes combine and energy is driven off.

5. List evidence that our understanding of black holes has changed.

Astronomers have found convincing evidence for a supermassive black hole in the center of the giant elliptical galaxy M87, as well as in several other galaxies. The discovery is based on velocity measurements of a whirlpool of hot gas orbiting the black hole. In 1994, Hubble Space Telescope data produced an unprecedented measurement of the mass of an unseen object at the center of M87. Based on the kinetic energy of the material whirling about the center (as in Wheeler's dance, see Question 4 above), the object is about 3 billion times the mass of our Sun and appears to be concentrated into a space smaller than our solar system.

For many years x-ray emission from the double-star system Cygnus X-1 convinced many astronomers that the system contains a black hole. With more precise measurements available recently, the evidence for a black hole in Cygnus X-1 is very strong.(site from the blog) It shows that we haven't known everything. The Hubble telescope discovered a lot for us.

6. Explain how Hubble Space Telescope's component cameras assist in the search for black holes.

A black hole cannot be viewed directly because light cannot escape it. Effects on the matter that surrounds it infer its presence. Matter swirling around a black hole heats up and emits radiation that can be detected. Around a stellar black hole this matter is composed of gas and dust. Around a supermassive black hole in the center of a galaxy the swirling disk is made of not only gas but also stars. An instrument aboard the Hubble Space Telescope, called the Space Telescope Imaging Spectrograph (STIS), was installed in February 1997. STIS is the space telescope's main "black hole hunter." A spectrograph uses prisms or diffraction gratings to split the incoming light into its rainbow pattern. The position and strength of the line in a spectrum gives scientists valuable information. STIS spans ultraviolet, visible, and near-infrared wavelengths. This instrument can take a spectrum of many places at once across the center of a galaxy. Each spectrum tells scientists how fast the stars and gas are swirling at that location. With that information, the central mass that the stars are orbiting can be calculated. The faster the stars go, the more massive the central object must be.(site from blog)

7. List at least 2 myths about black holes that are discredited.

The volume of a black hole approaches zero. As volume decreases, density increases. Density is the relationship of mass per unit of volume (Density = Mass/Volume). The density of a black hole affects the escape velocity of an object — even light.

Black holes have a broad range of masses — from the smallest (miniature) to the largest (supermassive).