Astronomy 201 Rice
University 2007 Fall Semester – Prof. Dufour
Problem Set 2
Part 1 – Three written problems (below) to be solved on paper and turned in on Thursday, September 20th by 5pm central time (turn in in class or under Dr. Dufour’s office door (346 HBH).
Part 2 – Two sets of multiple choice “basic skills and definitions quize” questions on material in Chapters 3 & 4. These are listed for course RICEASTR201F07 in masteringastronomy.com and are also due at 5pm central time that Thursday (submitted via the website).
Here are the three problems: [Note that useful unit conversion numbers and formulae are in Appendices A & B, respectively in CP4]
2-1: Halley’s comet orbits the Sun every 76.0 years and has an orbital eccentricity of 0.97.
a. Find its semimajor axis distance in astronomical units (AU).
b. Find its perihelion and aphelion distances (in AU).
c. Draw a reasonably accurate diagram of the orbit of Halley’s comet (an ellipse of course) and note the locations on it where it moves the fastest and slowest.
2-2: Suppose a star system has a single star that is four times as massive as our sun. If that system has a planet two times the mass of the Earth orbiting the star at an average distance of 1AU, what would be the period of the planet? (note that this is really a mathematically simple problem….don’t complicate it!)
2-3: Using
a. Pluto’s moon Charon orbits Pluto every 6.4 days with a semimajor axis of 19,700 km. Calculate the combined mass of Pluto and Charon. Compare this combined mass to the mass of the Earth which is about 6 X 1024 kg.
b. Calculate the orbital period of the Space Shuttle in an orbit 300km above the Earth’s surface.
c. The Sun orbits the center of the Milky Way Galaxy every 230 million years at a distance of about 28,000 light years. Use these facts to determine the mass of the Galaxy (in units of solar masses -- which we will see later is only the mass of the Galaxy inside of the Sun’s orbit).