FIVE astronomy topicsssssss. :D

Black Holes

A black hole is a super dense object that has an intense gravitational pull. There are two parts to a black hole, a singularity and a event horizon. Imagine a star which is much more massive than our sun, which is large enough to cause a black hole to form. What keeps this star from collapsing onto itself and becoming a black hole? The answer is that there is an intense pressure caused by nuclear reactions within the sun. When the fuel that feeds the nuclear reactions gets used up the massive star cannot support itself anymore. It then collapses to form a black hole.

Dark Matter

Dark matter is simply a name which astronomers give to any stuff in the universe which we can detect gravitationally but not actually see. In other words, the material is not emitting light of any wavelength which we can detect, but we can measure its gravitational effect on other objects in the universe. The first evidence of dark matter was found in clusters of galaxies back in the 1930's. Astronomer Fritz Zwicky discovered that the mass of luminous material in a cluster of galaxies was much less than the total mass of the cluster implied by the velocities of the galaxies.

Dark Energy

Dark energy entered the astronomical scene in 1998, after two groups of astronomers made a survey of exploding stars, or supernovas, in a number of distant galaxies. These researchers found that the supernovas were dimmer than they should have been, and that meant they were farther away than they should have been. The only way for that to happen, the astronomers realized, was if the expansion of the universe had sped up at some time in the past. No one really knows if it's anything or not. No can really explain it either.

Big Bang Theory

The Big Bang theory is an effort to explain what happened at the very beginning of our universe.

Pluto

In Roman mythology, Pluto (Greek: Hades) is the god of the underworld. The planet received this name perhaps because it's so far from the Sun that it is in perpetual darkness. After the discovery of Pluto, it was quickly determined that Pluto was too small to account for the discrepancies in the orbits of the other planets. Now, it is known as a dwarf planet.