PHYSICS 20A Lecture Notes - Lecture 1: Parsec, Astronomical Unit, Red Giant
Document Summary
There are 8 planets in our solar system: according to the official definition of planet in astronomy. Earth"s elliptical orbit around the sun is not the reason we experience seasons: see lecture 3. The eventual end of earth will naturally occur when the sun becomes a red giant and engulfs the. Almost every atom in your body was originally made inside stars. We have discovered over 1,000 planets outside our solar system. There is evidence for liquid water outside of earth. Our sun is approximately five billion years old. What"s the difference between astronomy and astrology: math. Earth is 1 1011 (100 billion) meters, or 1 au (astronomical unit) from the sun. Distances: 1 ly (lightyear) = 9 1015 (9,000,000,000,000,000) m. The closest stars are 5-10 ly away. 4. 5 1016 9 1016 m. 45,000,000,000,000,000 90,000,000,000,000,000 m: 1 pc (parsec) = 3 1016 (30,000,000,000,000,000) m. The closest galaxy is around 100 to 1,000 kpc (kilo-parsecs) away.
