Astronomy Assignment #10
Your Name______
Your Class Meeting Time ______
This assignment is due on Friday, 18 April (Note: There will be another assignment due on the following Monday.)
Submit this cover sheet with your assignment.
Complete the assigned problems from the text listed below and address the Instructor Assigned Topic. Mathematical problems may be hand written. Write out the problem, show your work in solving the problem and state your answer in a complete sentence. Failure to complete all three of these tasks will result in less than full credit awarded. The Instructor assigned topic must be typed.
Answer the following questions from the first half of Chapter 11 Determining Star Properties in Astronomy Notes.
Review Questions
1. Describe the procedure used to find distances to the nearby stars.
2. What do you need to know in order to get the scale of interstellar space in terms of kilometers or meters?
3. If the star-Sun distance = 30 parsecs, how far is the star from the Earth in light years…in kilometers?
4. If you measure the parallax of a star to be 0.1 arc second on Earth, how big would the parallax of the same star be for an observer on Mars (Mars-Sun distance = 1.5 A.U.)?
5. If you can measure angles as small as 1/50 arc second, how far out can you measure star distances from the Earth using the trigonometric parallax method? How long do you have to wait between observations?
6. If you can measure angles as small as 1/50 arc second, how far out can you measure star distances from Jupiter (Jupiter-Sun distance = 5.2 A.U.) using the trigonometric parallax method? However, how long do you have to wait between observations? (Use Kepler's third law to find Jupiter's orbital period and divide by two.)
Review Questions
1. Two identical stars have different apparent brightnesses (fluxes). One star is 10 parsecs away from us and the other is 30 parsecs away from you. Which star is brighter and by how many times?
2. Two identical stars have different fluxes. One star is 5 parsecs away from you and appears 81 times brighter than the other star. How far away is the dimmer star?
3. The Earth receives about 1380 Watts/meter2 of energy from the Sun. How much energy does Saturn receive from the Sun (Saturn-Sun distance = 9.5 A.U.)? (A Watt is a unit for the amount of energy generated or received every second.)
Review Questions
1. What does a magnitude interval of 5 correspond to in brightness? How about an interval of 1? How about an interval of 3?
2. Do bright things have larger or smaller magnitudes than fainter things?
3. How is apparent magnitude different from absolute magnitude?
4. Put the following objects (given with their apparent magnitudes) in order of brightness as seen from Earth (faintest first): Sun (-26.7), Venus (-4.4), Barnard's Star (9.5), Sirius (-1.4), Proxima Centauri (11.0).
5. You receive 8× 10-9 Watts/meter2 of energy from a star 2 parsecs away with an apparent magnitude = 1.3. What is the energy you receive from a star with an apparent magnitude = 5.3?
6. Two identical stars but star B is 10X farther away than star A. What is the difference in magnitudes between the two stars?
7. What two things does luminosity depend on?
8. If our Sun has luminosity = 1 solar luminosity, what is the luminosity of the following stars if they have the same diameter as the Sun (fill in the table):
star / temperature (K) / luminositySun / 6,000 / 1
A / 12,000
B / 2,000
C / 36,000
9. Some stars have temperatures of only 3000 K but have over 100X more luminosity than the Sun. How is this possible?
10. Would a red giant have a smaller or larger magnitude in a ``V'' filter than in a ``B'' filter? (Remember the first rule of magnitudes!)