Physics 202: Introduction to Astronomy

1
Physics 202 Introduction to Astronomy Lecture 2

• Carsten Denker
• Physics Department
• Center for SolarTerrestrial Research

2
Prologue

• Constellations
• Celestial sphere
• North and south celestial poles
• Celestial equator
• Celestial coordinates
• Declination and right ascension
• Solar and sidereal day

• Ecliptic
• Zodiac
• Seasons
• Summer and winter solstice
• Vernal and autumnal equinox
• Tropical and sidereal year
• Precession

3
Constellations in the Sky
4
Celestial Coordinates
5
Solar and Sidereal Day
6
Long-Term Changes ? Precession
7
Group Problem

• How and why does a day measured by the Sun differ
  from a day measured by the stars?
• Assume that the Earth would orbit the Sun in the
  opposite direction. How would that affect the
  solar and sidereal day?

8
The Orbit of the Moon

• Phases
• New, quarter, and full Moon
• Sidereal month (27.3 days) and synodic month
  (29.5 days)
• Solar and lunar eclipses
• Total, annular and partial solar eclipse
• Umbra and penumbra

9
Lunar Phases
10
Lunar Eclipse
11
Solar Eclipse
12
Group Problem

• Why arent there lunar and solar eclipses every
  month