Question

Write a paragraph on the birth and lifecycle of stars using figure 20.1.

Answer 1

Nebula is made up of gas and dust and is the birthplace of stars. Now, from this Nubula, various forms of stars are formed. Some are massive stars whose size is much greater than the size of Sun and some are smaller stars whose size is smaller than the size of Sun. Very large, massive stars burn their fuel much faster than smaller stars and may only last a few hundred thousand years. The smaller stars lasts for several billion years because they burn their fuel much more slowly. Other stages of a star during its life cycle is
Sun-like Stars: These are particularly similar to the sun in size but there is a lot of variation in terms of temperature. Examples are Alpha Centurai, Tau Ceti etc.
Red Giants: These stars do not have as hot outer layer as that of the Sun with temperature ranging from 3000 ^oC to 4000 ^oC but they have a very high luminance than the Sun. They are red in color and their diameter is 10 to 100 times that of the sun.
Super Nova: They are larger and even brighter as compared to the red giant stars and even the Sun. They are also considered as the primary source of heavy elements in the universe.
Binary or Twin Stars: A pair of two stars in which one revolves around the other or they both revolve around a common center is known as binary or twin stars.
Variable Stars: These stars have a variable shape and brightness i.e it keeps on changing whenever they expand or contract. Their brightness decreases when they expand and increases when they contract. Example Polaris or Pole Star.