Chapter 21 Origins of Modern Astronomy Word List:

Aphelion Astronomical unit Celestial sphere Constellations Declination Ecliptic Equatorial system Geocentric Heliocentric

Lunar eclipse Mean solar day Perihelion Perturbation Phases of the moon Plane of the ecliptic Precession Ptolemaic system Retrograde motion

Revolution Right ascension Rotation Sideral day Sideral month Solar eclipse Synodic month