Different Types of Stars
There are different types of star classifications. Brightness, color, temperature, age and spectrum are some of the characteristics that scientists use to classify stars. Stars may have several types of classification throughout their lives.
Main Sequence Stars:
The longest star stage is the main sequence stage. A star becomes a main sequence star after it is born. During this stage hydrogen atoms form with helium atoms and produce enormous amounts of energy. As long as stars have enough hydrogen to bond with helium their size changes very little. They stay in this stage until they start to loose hydrogen.
Giants and Supergiants:
The next stage a star may enter in its life is the giant, supergiant phase. One type of star in the giant phase is a red giant. A red giant expands and cools after using all of its hydrogen. After using its hydrogen the star's center shrinks and the atmosphere grows large and cools. Red giants are ten times bigger than the sun and supergiants are 100 times bigger than the sun.
White Dwarfs:
When stars get old and enter their final stages they shrink. They can become the same size as the sun or smaller. These types of stars are called white dwarfs. White dwarfs have no hydrogen left in them. Since they have no hydrogen they cannot produce energy. However, white dwarfs can still shine for billions of years before dying.
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