i) Print your name and Student ID number here.

Name: ID#:

ii) Sign your name here:

You will be using two blue books for this exam. Please put your name on both books. Please do problems 1-4 in one book and 5-8 in the other. We need to do this to be able to divide the grading between the TA and myself. Thanks for your cooperation!

This exam contains eight questions, each of which has multiple parts. PLEASE be sure to attempt each question as some questions are easier than others. You can spend an average of 15 minutes on each question and finish the exam on time. The exams will be collected at 10:10 pm.

Each of the questions is worth a total of 10 points. The point value of each of sub-part of a question are listed. You should use complete and clear sentences in your explanation and discussions. Show all of your work in numerical problems and include the UNITS in your answer.

1. Descriptions...

a. (3 pts) How are the equinoxes defined and when do they occur?

b. (4 pts) What is differentiation as applied to planetary structure? Give an example.

c. (3 pts) What are sunspots and what causes them?

2. Broad Trends in the Solar System

a. (4pts) Explain the differences between our Moon and the moons of Saturn. Why are there these differences?

b. (4pts) What are the differences between asteroids and comets and what do these differences indicate about their origins?

c. (2pts) Give two significant differences between terrestrial and jovian planets.

3. You have just discovered the planet Z22 located around a star with a luminosity 100 times that of the Sun.

a. (3pts) Your newly discovered planet has an Earth-like atmosphere and is located 3 AU from the star. What do you expect for the surface temperature of the planet? Do you step out of your spacecraft wearing a swimsuit or a parka?

b. (3pts) After you exit the spacecraft, you notice that there is a moon. That night you measure the moon to move by 4 degree relative to nearby stars in 10 hours. What is the period of the moon?

c. (4pts) Next, you pull out your trusty scale and weight yourself. You weight 25% more than you do on Earth. Calculate the scale height of the atmosphere for the surface temperature calculated in part a of this question.

4. What evidence is there for the following statements. Consider both direct observational evidence and physical laws. Give two lines of evidence for each in parts a, b, and c.

a. (3pts) The Solar System is roughly 4.5 billion years old.

b. (3pts) Greenhouse gases can cause increased atmospheric temperatures.

c. (3pts) The energy of the Sun is generated by fusion reactions in its core.

d. (1pt) Give one reason why we think the Sun will shine as it does now for another few billion years.

5. A new comet is found whose orbit comes within 0.4 AU of the Sun at closest approach and is 120 AU from the Sun at the farthest point in its orbit.

a. (3pts) What is the period of the comet?

b. (3pts) Assuming that the comet is mainly composed of ices that evaporate at 170 K, at what distance from the Sun would you expect the comet to start evaporating and growing a tail?

c. (4pts) What would you expect the luminosity of the comet to be at a distance of 50 AU from the Sun? Assume that the comet nucleus has a radius of 10 km. At what wavelength would the emission peak?

6. You are a colonist on the planet Mars. Various information about Mars is given on the cheat-sheet. In addition, the rotation period of Mars is 24.6 Earth-hours.

a. (4pts) What will be the difference between the sidereal and solar days on Mars? Give you answer in Earth-minutes per Martian day.

b. (3pts) You are assigned the job of building a solar light collector to supply the energy needs of the colony. Your colony needs 100 kilowatts (100,000 Joules/second) of electricity to survive. Assuming that you can convert sunlight into electrical energy with 20% efficiency, how much area will you need to cover with your solar collector panels?

c. (3pts) What is the current atmosphere of Mars like and what considerations would you face in trying to make the atmosphere breathable?

7. More things to explain....

a. (4pts) Explain the scientific method. Explicitly outline the steps of the scientific method.

b. (3pts) Is this statement true or false, ``we can never see from Earth the face of Mars fully illuminated (a full-Mars like the full-Moon)''. Explain your answer.

c. (3pts) How are planetary ring systems created and why are they nearly perfect rings?

8. Understanding the origins of our solar system.

a. (4pts) Explain how the convervation law for angular momentum can be used to understand some aspects of the structure of the forming solar system.

b. (3pts) If the nearest star, Proxima Centauri, had a planet with a period of 2.5 years and an amplitude to its radial velocity variations of 50 m/sec over the course of an orbit, what would be the mass and the orbital radius of the planet? Proxima Centauri has a luminosity of 10^-4 times the Sun and a mass of 0.3 solar masses.

c. (3pts) Proxima Centauri is so much dimmer than the Sun that it might be possible to image such a planet if it existed. What size telescope would you need to resolve the planet from Proxima Centauri if you observe at a wavelength of 10 microns? Proxima Centauri is 4.3 light-years ( meters) from the Sun.