AST 2002 Chapter Notes - Chapter 12: Williamina Fleming, Stellar Classification, Cosmic Dust
Document Summary
Stars are born from clouds of interstellar gas. Stars sign by nuclear fusion for millions to billions of years. We only see a brief moment in any star"s life. Stars have a lot in common with the sun: stars form in great clouds of gas and dust, by hydrogen and helium (by mass) They differ in size, age, brightness, and temperature. Three fundamental properties of stars: luminosity, surface temperature, mass. We can use some to identify constellations. Some are so dim that we can"t see them. Brightness of a star depends on its distance. Two similar-looking stars can generate very different amounts of light. Apparent brightness: how bright the star appears to a detector on earth; the amount of power (energy per second) reaching us per unit area. Luminosity: how bright stars are in an absolute sense regardless of their distance; the total amount of power that a star emits into space: standard units of luminosity are watts.
