Astronomy 115 Spring 2000 Name:_________________________________________

HW#1 Due Feb 17

Use scientific notation and MKS Units unless otherwise stated. Round your answers off to no more than 3 digits. For problems from the text, write your answers on separate sheets of paper and STAPLE to this. For full credit you must show all your wor k.

Ch1: Review Questions 7, 9; Problems 2, 4 Ch2: Review Questions 2, 13; Problems 1, 3, 4 Ch12: Problem 3

1. The average orbital radius of the moon is approximately 3.84 x 10⁵ km. How many miles is it? (1 mi = 1.6 km)

2. How many Earth-moon distances (orbital radii) would it take to reach from the Earth to the Sun?

That is, how many lunar orbital radii fit in one AU (1 AU = 1.5x10⁸ km)?

3. A light year (ly) is 9.46 x 10¹⁵ m. How many miles are in a light year? (1 mi = 1.6 km)

4. How many AUs are in a light year?

5. The Milky Way Galaxy is approximately 100,000 lys across. How many AUs is that? That is, how many sun-earth distances would you have to put end to end to span the distance of the Milky Way?

6. The speed of light is c = 3 x 10⁸ m/s. How long does it take for light to travel from the Sun to the Earth?

(Recall that speed = distance/time so time = distance/speed or t = d/s)

7. How long does it take for light to travel from the Moon to the Earth?

8. If the diameter of a H atom is 10^-10 m, how many seconds does it take for light to travel across a H atom?

9. How many H atoms would you have to line up edge to edge to reach from the Earth to the Sun?

Use the data in the Appendix and in your reading to answer the following.

10. List the Planets in order of increasing distance from the sun.

11. List the Planets in order of increasing size (diameter).

12. List the Planets in order of increasing mass.

13. Which are the Jovian planets? Which are the Terrestrial Planets?

14. If you made a scale solar system with the sun the size of an orange (5 cm in diameter), how big would Jupiter be?

15. How far away from the orange would the scaled version of Jupiter be placed?

16. What is the apparent magnitude scale a scale of? What is meant by 'apparent'?

17. The apparent magnitude of the sun is –27 and the apparent magnitude of the full moon is –12.

How much more intense is the sun than the full moon? (Use table 2-1)

18. What defines the celestial sphere and celestial poles?

19. The Sun appears to rise in the a) north b) south c) west d) east and set in the a) north b) south c) west d) east.

But in reality, the Earth is rotating from a) north b) south c) west d) east to a) north b) south c) west d) east.

20. If a star is directly over head in the sky, it is at the a) celestial equator b) north celestial pole c) horizon d) zenith

If you were on the equator, directly overhead would be the a) celestial equator b) north celestial pole c) south celestial pole and on the northern horizon would be the a) celestial equator b) north celestial pole c) south celestial pole