Methods Astronomers used to measure the Universe
According to Space Encyclopedia, astronomers have devised three main methods to measure distance in space. They are parallax measurement, brightness measurement and red shift measurement. The Parallax measurement is used to determine the distances to about 10,000 of the nearest stars. When viewed from two widely separated points a nearby star appears to shift its position slightly against the background of more distant stars. The star parallax is the angle it would appear to move across the sky if viewed from two points that are 1 astronomical unit (AU) apart. Astronomers use a unit of distance that relates directly to parallax. This unit is called parsec. One parsec is the distance to a star that has a parallax of one second of arc. One parsec equals 3.26 light years. Parallax can be used to measure distance up to about 300 parsecs, which is less than 5 percent of the distance to the center of the Milky Way (Couper, 841).
Astronomers can determine the distance to certain stars by comparing their luminosity with their apparent brightness as observed with a telescope. This type of measurement is based on the fact that the greater the distance to a star of a given luminosity, the fainter the star appears from the earth. Astronomers commonly use brightness measurements to calculate distance to some kinds of variable stars. Each of these stars goes through a cycle of variation in brightness during a specific period of time. Astronomers have discovered that the length of this period indicates the luminosity of the star. Astronomers also look for objects of known brightness even beyond the region where they can detect individual stars (Pasachoff, 46).For example, the brightest galaxy in any other cluster of galaxies has about the same luminosity as the brightest galaxy in any other cluster. Comparing this luminosity with the apparent brightness is the best method for measuring the …

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