Lecture 3: Astronomy as a Science

Question 1

European development of astronomy

Answer 1

• Copernicus developed the heliocentric model, believed the earth rotated on its own axis, and that all planets’ orbit’s are circular
• Tycho Brahe had very detailed and high-precision observations
• Kepler’s 3 laws, where all orbits are elliptical, equal areas are swept out in equal time, and period squared = semi-major axis cubed

Question 2

Planetary positions / Motions (Synodic)

Answer 2

• Elongation is the angle of the planet with respect to the sun
• Conjunction is when the planet has elongation of 0º
• Opposition is when planet has elongation of 180º
• Quadrature is when the planet has elongation 90º (superior planet only)

Question 3

Sidereal vs. Synodic Periods

Answer 3

For a superior planet:
- S = 1 + S/P
For an inferior planet
- S + 1 = S/P

Question 4

Ellipses

Answer 4

• Eccentricity is equal to distance to a focus divided by the object’s semi-major axis