TYPES OF GALAXIES: There are four classifications of galaxies: spiral, which is a central disk surrounded by a wavy pattern of material; lenticular, which consists of the disk of a spiral galaxy without the surrounding spiral structure; elliptical, which have elongated round shapes; and irregular, which do not fit into the above categories, often because they are distorted by gravitational forces from other astronomical objects.
HOW TELESCOPES WORK: The basic objective of a telescope is to increase the visibility of faraway objects, such as stars. By magnifying the size and brightness of objects, telescopes increase the chance that users will be able to spy items in space. Optical telescopes are what people usually refer to simply as telescopes, the type that magnify the light from faraway objects, but there are other types. These telescopes search for x-rays, gamma rays, or radio waves to help astronomers gather additional information about the universe. The earliest type of optical telescope is called a refracting telescope, which is still used today, for example in a pair of binoculars. The simplest telescope of this type would be two lenses spaced a distance apart. The first lens refracts or bends light so that the rays will converge at a single point (creating a focus), while the other lens (at the eyepiece) is the one that spreads out the light and magnifies it for your eye to see. Reflecting telescopes use curved mirrors to magnify images. This type of telescope was developed after the refracting telescope, and corrected for a problem called chromatic aberration, which causes false colors to appear around the edges of objects -- a big problem when trying to look at the sky!
The American Geophysical Union contributed to the information contained in the TV portion of this report.