# ASTR 109 HOMEWORK #2 (Hamilton) due Wednesday July 30

1. Go to the Earth's Seasons webtool at http://janus.astro.umd.edu/astro/seasons website.
a) Run the defaults for Christchurch (latitude 43.5 degrees south). How many hours of sunlight do we get in mid summer? Mid winter?
b) How do these numbers change for Dr. Hamilton's hometown of Anchorage Alaska at latitude 60 degrees north?
c) Describe the amount of sunlight received during the year for someone at the equator.
d) What is special about the Antarctic Circle and the Tropic of Capricorn?
e) Explore seasons on a few of the other planets - what if Earth were tilted like Mercury or Uranus (see helpfile)?
f) Finally, under what conditions would Earth's Antarctic Circle be north of its Tropic of Capricorn?

2. Changing Perspectives: A view from the Moon. The same side of the Moon always faces the Earth. Assume you live on the Moon near the centre of the face that points towards Earth.
a) Where in your sky would you see the Earth?
b) Describe how the Earth would appear to move in the sky.
c) Suppose you see a full Earth in your sky. What phase of the Moon would people of the Earth see? Draw a picture and explain.
d) Suppose people of Earth see a full Moon. What phase would you see for the Earth? Draw a picture and explain.
e) Suppose people on Earth are viewing a total lunar eclipse. What would you see from your home on the Moon? Explain.

3. Explore the Solar System. The Solar System consists of planets and minor bodies (asteroids and comets) that orbit the Sun and moons that orbit the planets. Go to the Solar System Visualizer program at http://janus.astro.umd.edu/SolarSystems. Start with the Solar System, using the + and - keys to zoom in and out.
a) Which way do the planets orbit the Sun, clockwise or counterclockwise?
b) Now click on each of the planet names in the upper left menu (if nothing happens, the planet has no moons). How many moons do the terrestrial planets Mercury, Venus, Earth, and Mars have? Do these orbit clockwise or counterclockwise?
c) Now look at each of the giant planets - what are the main differences between the satellite systems of the terrestrial and giant planets?
d) Finally, check out Pluto. In terms of moons, is Pluto more like a terrestrial or giant planet?