Do Stars Evolve?Some of what astronomers describe as "stellar evolution" does take place. However, the process is misnamed, and parts of it are questionable.
According to this theory, the life of a star is said to begin with the collapse of a gas cloud--a doubtful beginning, as explained in Do new stars form today?. Bypassing this fundamental origin problem, a young star is said to begin in the "main-sequence" category. These are average stars with a stable light output. The great majority of stars are in the main sequence, including our sun. Then when a star's hydrogen fuel runs low, it becomes a red giant or super-giant star. The star expands hundreds of times in size and becomes somewhat cooler. Red giants include Betelgeuse and Aldebaran. Next, the star may either explode as a supernova or may slowly collapse into a small, hot white dwarf star. The companion star circling Sirius is such a dwarf. Such stars are said to be very old.
This article adapted from the book,
The Bible and Astronomy
written by Dr. Donald DeYoung.