Stars
A star is a giant, luminous sphere of plasma held together by its gravity. They usually live for billions of years, but some can live for a only a few million.
How They Form
A star's life begins with the gravitational collapse of a gaseous nebula. Stars begin as clouds made of cold molecular hydrogen and helium. These clouds contain other elements from stars that lived and died long ago. These elements are held inside these clouds by their inward force of gravity and the outward pressure of molecules. Eventually something overcomes this balance and the cloud falls apart. This is usually caused by supernovae or a collision with another gaseous nebula. As the cloud is collapsing it breaks apart into smaller clumps and the stars begin to form out of these clumps. Based on the amount of material inside these clumps determines what type of star it is.
Death
A star's death can come in two forms: a supernova and a hyper nova. The core of the star will suddenly collapse as its electrons are driven into its protons, forming neutrons. The shock wave formed by this sudden collapse causes the star to explode in a supernova. Supernovae are so bright that they outshine the star's entire home galaxy. If a star is big enough (hyper giant) then it will instead explode into a hyper novae instead.
The Star Eta Carinaeu is in the process of exploding into a supernova
The life cycle of a star
Diagram of the Sun
Stellar Spectral Types
Stars are classified by groups by type, color, and average temperature.
Type: O
Color: Blue
Average Temperature 80,000 (Fahrenheit) 45,000 (Celsius)
Color: Blue
Average Temperature 80,000 (Fahrenheit) 45,000 (Celsius)
Type: B
Color: Bluish White
Average Temperature: 55,000 (Fahrenheit) 30,000 (Celsius)
Color: Bluish White
Average Temperature: 55,000 (Fahrenheit) 30,000 (Celsius)
Type: A
Color: White
Average Temperature: 22,000 (Fahrenheit) 12,000 (Celsius)
Color: White
Average Temperature: 22,000 (Fahrenheit) 12,000 (Celsius)
Type: F
Color: Yellowish White
Average Temperature: 14,000 (Fahrenheit) 8,000 (Celsius)
Color: Yellowish White
Average Temperature: 14,000 (Fahrenheit) 8,000 (Celsius)
Type: G
Color: Yellow
Average Temperature: 12,000 (Fahrenheit) 6,500 (Celsius)
Color: Yellow
Average Temperature: 12,000 (Fahrenheit) 6,500 (Celsius)
Type: K
Color: Orange
Average Temperature: 9,000 (Fahrenheit) 5,000 Celsius)
Color: Orange
Average Temperature: 9,000 (Fahrenheit) 5,000 Celsius)
Type: M
Color: Red
Average Temperature: 6,500 (Fahrenheit) 3,500 (Celsius)
Color: Red
Average Temperature: 6,500 (Fahrenheit) 3,500 (Celsius)