2StarLifeCycle

StarLifeCycle Stars expand as they grow old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright. Stars: .
 * stars are born in nebula. Huge clouds of dust and gas collapse under gravitational forces, forming protostars.
 * The pleiades is the brightest star on earth.
 * Aldebaran is the 13th brightest star in constelation tauras.
 * A star is a ball of gas held together by it's own gravity.
 * stars that are 25 to 50 times that of the sun lives for only a few million years.
 * The hydrogen gas in the nebula is pull together by gravity and it begins to spin.
 * As the gas spins faster, it heats up and become as a protostar
 * This is a red giant or a red super giant (depending on the initial mass of the star). It will eventually collapse and explode.
 * It's fate is determined by the original mass star ; it will become either a black dwarf, neutron star, or a black hole.
 * Contained in the milky way are stars, clouds of dust and gas called nebulae, planets, and asteriods.
 * The milky way is approximately 100,000 light-years in diameter.
 * Our solar system is 26,000 light-years from the center of the galaxy.
 * It takes 250 million years for our sun (and the earth with it) to make one revolution around the center of the milky way.
 * Orion Belt:
 * The orion nebula messier 42 is the brightest starforming, and the brightest diffuse nebula in the sky, and also one of the brightest deepsky objects at all.
 * The distance is 1.3(kly)
 * The visual brightness is 4.0 (mag)
 * The apparent dimension 85x60 (arc min)
 * The declination is -05:27 (deg:m)