M 97 (NGC 3587) is commonly known
as the Owl Nebla. It lies 2 thousand light years away in the constellation
of Ursa Major, the Big Bear. It was discovered by Pierre Mechain
in 1781 and Charles Messier added it to his catalog that same year.
M 97 is a planetary nebula. These
are formed when a small to intermediate-sized star exhausts its
supply of Hydrogen and begins converting Helium into heavier elements
(i.e., Carbon, Oxygen). This causes the star to expand into a red
giant. The temperature of the star's core increases and its stellar
winds further expand the outer shell. It then reaches the point
where the expanding gases become ionized and begin to glow. Planetary
nebula are relative short-lived, approximately 25,000 years.