ASTRONOMY 3: Introductory Astronomy: The Solar System

Winter 2012

Lecture 2:

Apparency of the sky

celestial sphere: winter and summer constellations

Northern and southern hemisphere sky: celestial poles, zenith, and horizon

Inferences based on the stellar positions.

daily motion of the stars and the Sun: Earth spins

Seasonal cycles: The Earth's spin axis is not exactly perpendicular to its orbital plane around the Sun.

Bright side of the Moon always faces the Sun: the Moon is illuminated by the Sun.

Phases of the Moon: the Moon orbits around the Earth once every thirty days or so

Solar and lunar eclipse: alignment of the Sun-Earth-Moon system

Discovery of Planetary Environment and Paradigm shifts

The motion of heavenly bodies are measurable and predictable

The Earth is not at the center of the Universe

Planetary surface and interior are complex and evolving

Planets are ubiquitous and planetary systems have diverse properties

Historic Milestones:

Eratosthenes measured the radius of the Earth in 200 BC: the zenith at Alexandria and Syene

Planets as wanderers amount the stars

Ptolemy postulated the geocentric model of the Solar System in 140 AD: no measurable parallax

Epicycles: attempts to account for planets' retrograde motion

Copernicus laid the foundation of heliocentric cosmology around 1500 AD: planets' retrograde motion

Galileo used the telescope for astronomical observation around 1600 AD: phases of Venus

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