AST 2002 Chapter 12: Chapter 12
Document Summary
Stars are born from clouds of interstellar gas. Stars sign by nuclear fusion for millions to billions of years. We o(cid:374)ly see a (cid:271)(cid:396)ief (cid:373)o(cid:373)e(cid:374)t i(cid:374) a(cid:374)y sta(cid:396)"s life. Stars have a lot in common with the sun. Stars form in great clouds of gas and dust. Three quarters hydrogen and one quarter 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. O(cid:373)e a(cid:396)e so di(cid:373) that (cid:449)e (cid:272)a(cid:374)"t see the(cid:373) 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.
