Stars

What is a star? The objects that heat and light the planets in a system A star is a ball of plasma held together by its own gravity Nuclear reactions occur in stars (H  He) Energy from the nuclear reactions is released as electromagnetic radiation

Characteristics of Stars Magnitude (brightness) A measure of brightness of celestial objects Smaller values represent brighter objects than larger values Apparent magnitude How bright a star appears to be from Earth Absolute magnitude (luminosity) How bright a star actually is

Temperature & Color The color of a star indicates the Temperature of the star Stars are classified by Temperature Decreasing T (bright to dim) O, B, A, F, G, K, M [Oh Be A Fine Girl, Kiss Me ]

Classification of Stars Temperature Color O 20,000- 60,000 K Blue B 10,000 – 30,000 K Blue-white A 7,500 – 10,000 K White F 6,000 – 7,500 K Yellow-white G 5,000 – 6,000 K Yellow K 3,500 – 5,000 K Orange M 2,000 – 3,500 K Red

Life Cycle of Stars Life span of a star depends on its size. Very large, massive stars burn their fuel much faster than smaller stars Their main sequence may last only a few hundred thousand years Smaller stars will live on for billions of years because they burn their fuel much more slowly Eventually, the star's fuel will begin to run out.

One light-year is equal to 6,000,000,000,000 miles Closest Star Proxima Centauri One light-year is equal to 6,000,000,000,000 miles (9,500,000,000,000 kilometers.

What Do We Know About The Universe Hubble Telescope

Nearest Galaxy