Astronomy and Astrophysics

Cool Site! - Be sure to check out nineplanets.org for great images of and facts about our sun, our neighboring planets, and the rest of the solar system. (It's where most of these images come from!)

Cool Site! - For nebulae, galaxies, and clusters be sure to check out the SEDS collection of Messier objects.

• Scientific Notation
• Since astronomical measurements tend to be, well, astronomical in size, we use a shorthand for very large or very small numbers.
• 1,000,000,000 = 1.0 * 10⁹ = 1.0E9
• 1/1,000,000,000 = .000000001 = 1.0 * 10^-9 = 1.0E-9

• Short Tour of the Solar System
• Earth
• M_Earth = 6E24 kg
• R_Earth 6500 km
• Distance fom Sun = 1 AU = 1.5E08 km
• Earth at night
• Sun
• M_Sun = 2E30 kg
• R_Sun = 7E5 km
• T_Sun = 5800 K
• Mercury R=0.38 R_Earth  M=0.06 M_Earth D=0.39 AU V=47.9 km/s
• Venus R = 0.95 M = 0.81 D = 0.72 V = 35.0
• Volcanic Domes
• Mars R = 0.53 M = 0.11 D = 1.52 V = 24.1
• Asteroid Belt D=2.6 AU
• Jupiter R =11.21 M = 317.9 D = 5.2 V = 13.1
• Saturn R = 9.45 M = 95.18 D = 9.54 V = 9.64
• Uranus R = 4.01 M = 14.54 D = 19.19 V = 6.81
• Neptune R = 3.88 M = 17.13 D = 30.06 V = 5.43
• Pluto R = 0.18 M = 0.025 D = 39.53 V = 4.74
• Kuiper Belt D = 50 ? 100 AU
• Halley's Comet
• Oort Cloud D = 50000 ? 100000 AU
• Shoemaker-Levy 9

• Nearest Star: Alpha Centauri (Proxima Centauri 1.3 pc)
• 1 ly = 1E13 km
• 1 pc = 31.E13 km, 3.3 ly
• c = 3E5 km/s
• Center of the Galaxy 8 kpc
• Nearest Galaxy: Andromeda, 1 million parsecs away, or 1000 kpc
• Hubble Deep Field ? How far can we see?
• speed of light c = 3E5 km/s, age of universe is 14 billion years, or 4.42E17 s
• 1e23 km, 10,000,000,000 ly, so “edge” of universe is roughly 10,000 times further away than nearest galaxy, 5,000,000,000 times further than nearest star, 1,000,000,000,000,000 times further away than sun. 1,000,000,000,000,000,000,000 times further away than Durham.