Homework 1
Due: Thursday, 4th April.
Chapter 1 From Chaisson and McMillan
Show your work when required!
1. b) Draw a sketch of the Earth and the celestial sphere. Mark on the North Pole, South Pole, Equator, Antarctic and Arctic Circles, Tropics of Cancer and Capricorn, the North and South Celestial Poles, the Celestial Equator. (4 marks)
2. a) If the skies were cloudless, how many nights per year would the star Polaris be visible from Philadelphia? (1 mark)
2. b) If you always observed Polaris from the same place in Philadelphia, would you always see it in the same place on the sky? Why or why not? (2 marks)
2. c) Why is it warm in summer in Philadelphia and cold in winter?(2 marks)
3. a) Express these numbers in power of 10 notation
one hundred million, eighty thousand, seven one-thousandths (0.007), thirty-five billion (2 marks)
3. b) Express 2 arc-seconds in arc-minutes and also in degrees(1 mark).
3. c) We see a planet at a distance of 5AU's. It subtends an angle of 10 arc mins. We move this planet to a distance of 10AU's, what angle does it now subtend?(2 marks)
4. a) Define a parsec, an astronomical unit and a light year (a sketch may help you define the parsec). Note these are all distance measurements.(3 marks)
4. b) There are 3.26 ly to 1 pc. How far away in light years would an object at a distance of 15pc lie?(1 mark)
4. c.) One AU is 1.496 x 10^8 km. One light year is 9.46 x 10^12 km. By what factor is a light year larger than an AU?(1 mark)
5. a) It is sunset in Philadelphia and you are facing East. You see the moon on the horizon. Draw a diagram of the Earth/Moon/Sun system looking down at the plane of the solar system. What is the phase of the moon (Hint in which direction does the sun set)?(3 marks)
5. b) When you are observing the Moon in problem 5a, a friend asks you when the soonest (i.e. in how many nights time) you could possibly see a solar eclipse? And a lunar eclipse?(2 marks)
5. c) After this time, the friend complained that they didn't see a lunar eclipse. Give one explanation why not.(1 mark)
5. d) Give a different reason for why the friend may not have seen a solar eclipse.(1 mark)
Total 30 marks