Characteristics of Stars

Star Definition

• Star – A body of gases consisting mainly of hydrogen and helium that gives off a tremendous amount of energy (electromagnetic radiation)

Star Color – Depends upon surface temperature

Blue stars – above 30,000 CWhite stars – 8,000 - 11,000 CYellow stars – about 5,550 C (sun) Orange stars – about 4,000 CRed stars – about 3000 C

Star Color

Star Size

• Vary from dwarf stars (size of the earth) to super giants that are 1000 times bigger than sun

Star sizes

Brightness of stars (magnitude)

Absolute Magnitude – true brightness of a star – Depends upon temperature and size

Apparent magnitude – brightness of a star as viewed from earth. Depends upon temperature, size, and distance to earth

Absolute magnitude

Classification of Stars – Hertzsprung-Russell (H-R) diagram – Comparison of absolute magnitude and temperature of stars.

• Main Sequence -most common star – (sun)

• Red Giants - very large, cool bright star• Supergiants - extremely large bright star• White dwarf – small, hot, dim star

H-R Diagram