ASTRO 104 Study Guide - Quiz Guide: Retrograde And Prograde Motion, Angular Distance
Document Summary
Destination 2: mars: motions of the planets: Retrograde motion: visual phenomenon where planets appear to move west east, stop, move east west, stop, then continue west east (with respect to the stars) Observed because of the different orbital speeds of the planets and difference in period (kepler"s 1st and 2nd laws) Occurs because planets with small orbits move faster than planets with large orbits (when orbits are closed): true in all cases when body is farther from sun. Inferior planets (innermost, mercury and venus): always seem close to the sun in the sky because of their small angular separation from the sun as viewed from earth never appear far above the horizon: phobos and deimos. Moon: larger than both phobos and deimos, farther from earth. How are a body"s orbital period and orbital radius related? a=semiorbital axis (radius); p=period. For the solar system: a^3=p^2 (if period is measured in years and a is measured in.
