Astro 101-003 Regener Fall 2012

Assigmnent #1

Due: Tuesday 9/25, start of class (1100 am MDT)

  1. Just before the Copernican theory became popular, the most widely held idea about the motion of the planets was that (a) they orbited the Earth directly, in circles; (b) they orbited in epicycles that orbited the Earth; (c) everything orbited the Sun; (d) everything except the Earth orbited the Sun.
  2. Name the celestial coordinate that is analogous to latitude.
  3. Name the celestial coordinate that is analogous to longitude.
  4. The reason why the sidereal day and the solar day are not the same is (a) because Earth both spins on its axis and orbits the Sun; (b) because the constellations are moving with respect to the solar system; (c) because the Moon slows the Earth’s rotation; (d) because Earth’s orbit is elliptical.
  5. Kepler’s 3rd law of planetary motion states that the square of a planet’s period (its “year”) is proportional to the _____ of the semi-major axis of its orbit.
  6. Place these regions of the electromagnetic spectrum in the proper order from shortest to longest wavelength: Xray; visible; radio; gamma ray; infrared.
  7. The Doppler effect indicates that (a) as a star moves towards us its light is shifted to be more blue; (b) as a star recedes from us its light is shifted to be more red; (c) can be used to indicate that one or more planets are orbiting another star; (d) all of a-c are true; (e) none of a-c are true.
  8. What are the two most important performance criteria of a modern astronomical telescope? (Hint, neither of them is “magnification”).
  9. Two telescopes with the same diameter D are being evaluated. One of them works in visible light, and one of them works in the infrared. Which one has better resolution on the sky (as measured by the smallest angle it can resolve)?
  10. Ultraviolet astronomy is very difficult to do from the ground because: (a) the optics must be cooled to very cold temperatures; (b) the atmosphere absorbs much of the ultraviolet light from stars, preventing it from reaching the telescope; (c) the atmosphere at ground level degrades the mirrors, making them unusable; (d) suitable detectors do not exist.
  11. Which two planets have the most eccentric orbits in the solar system?
  12. What are two key differences between Terrestrial planets and Jovian planets?
  13. The most distant feature of our solar system is (a) the “planet” Pluto; (b) the Kuiper Belt; (c) the asteroid belt; (d) the Oort cloud.
  14. Comets have two types of tails, name them (one word each).