AS101 Lecture Notes - Lecture 1: Spiral Galaxy, Angular Diameter, Local Group
Document Summary
Solar system the sun, its planets, and smaller bodies (moons, asteroids, comets etc. ) Alpha centauri is the closest solar system to ours and its 4. 6ly (light years) away. Planet a non-luminous body in orbit around a star, large enough to be spherical and to have cleared its orbital zone of other objects. Star a globs of gas held together by its own gravity and supported by the internal pressure of its hot gasses, which generate energy by nuclear fusion. **key difference between planets and stars = stars generate their own light whereas planets shine by reflecting sunlight. Galaxy a large system of stars, star clusters, gas dust and nebulae orbiting a common center of mass. The milky way hazy band of light that circles our sky, produced by the glow of our galaxy. Milky way galaxy the spiral galaxy containing our sun -it contains approximately 100x10 stars, has a diameter of 80,000ly and is larger and older than most galaxies.
