ASTR 100Lgx Lecture Notes - Lecture 1: Interstellar Cloud, Observable Universe, Galactic Center
Document Summary
Star a large, glowing ball of gas that generates heat and light through nuclear fusion. Planet a moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition. Moon (satellite) an object that orbits a planet. Asteroid a relatively small and rocky object that orbits a star. Solar system a star and all the material that orbits it, including its planets, moons, asteroids, comets, etc. Nebula an interstellar cloud of gas and/or dust. Galaxy a great island" of stars in space, all held together by gravity and orbiting a common centre. Universe the sum total of all matter and energy that is everything within and between all galaxies. Scientific notation: lots of zeroes required, used often, 10 = 1. 0 x 10^1, ex. 1 billion = 1,000,000,000 = 1. 0 x 10^9 ex.
