Astronomy
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 stars with the least mass are red and much cooler than other stars. Carbon burning can develop at the star's center and a complex set of element burning shells can develop towards the end of the star's life. This idea of light as a wave was popular because it explained experiments in which light created a series of bright and dark limes called an interference pattern. This makes the star appear brighter and cooler and it becomes a red giant. A star one tenth of the Sun's mass will only be 1/10,000th of its brightness but will last 1,000,000,000,000 years (James, 41). They become brighter and cooler on the outside and are called red super giants. Beyond Neptune, the planetesimals never managed to collide and grow into larger planets, like Pluto (Altschuler, 60-61). Space Encyclopedia DK Publishing, Inc. As was said above, these stars go through their evolutionary stages very quickly compared to the Sun. Unlike other kinds of waves, light waves in a vacuum have one speed, and that speed is the faster that anything can travel. During the red giant phase a star often loses a lot of its outer layers which are blown away by the radiation coming from below. This disk extended to a very large distance, tens of times farther than the orbit of Pluto. The birthplaces of stars are dark, cool interstellar clouds, which are comparatively rich in dust and gases. : NY 1999 Measuring the Expansion Rate of the Universe.
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