PY 124: Solar System Astronomy: Homework 1

1) Define Right Ascension

2) Define Declination

3) Explain the relationship between local sidereal time and right ascension.

4) Why is a sidereal day different in length from a mean solar day? (Also, which is longer?)

5) The full Moon is just crossing your meridian. About what time is it? (Sunrise, midmorning, noon, mid-afternoon, sunset, mid-evening, midnight)

6) A third quarter Moon is just setting. About what time is it? (Sunrise, midmorning, noon, mid-afternoon, sunset, mid-evening, midnight)

7) You are lost at sea. You look up and find the North Star (Polaris). Luckily you remember how to measure angles from your astronomy lab, and you measure the altitude of Polaris to be 32 degrees. Do you know your latitude from this? If so, what is your latitude?

Do you know your longitude from this? If so, what is your longitude?

8) Give two observations that you can make with your bare eyes (no satellite views, etc...) that indicate that the Earth is round.

9) How many arc seconds are there in a degree?

10) What is the Ecliptic?

11) What is Apparent Solar Time?

12) Define an Astronomical Unit.

13) In Kepler's equation P2 = ka3, what do the letters "P" and "a" represent?

14) If we wish to simplify our calculations using Kepler's equation P2 = ka3, what units do we use for P and a to make k=1?

15) Is the space shuttle being "pulled" (being influenced) by Earth's gravity while in orbit? Explain.

16) Why is the summer warmer than the winter?

17) A given star has a declination of 35° north. If you are located at 52° north latitude, is this star in the circumpolar zone as you see it? Explain why or why not.

18) A given star is just touching your horizon just below Polaris. This star has a declination of 62° . What is your latitude?

19) You are located at 45° west longitude. If it is 3:00 PM (15:00 UT) in Greenwich, what is the local apparent solar time where you are?

20) If the sun transits Greenwich at 11:55 UT, and it transits your local meridian at 05:55 UT, what is your longitude?

21) When do each of the following occur?

Vernal Equinox;

Summer Solstice;

Autumnal Equinox;

Winter Solstice

22) What actually happens on the celestial sphere to define each of the following?

Vernal Equinox;

Summer Solstice;

Autumnal Equinox;

Winter Solstice

23) A star with a Right Ascension of 20h 15m transited your local meridian 1 hour ago. What is your local sidereal time?

24) A new star catalogue lists the following information on several stars:

Designation and Constellation / Apparent Magnitude


a Pegasi / 2.5

b Pegasi / 0.5

g Pegasi / 1.5

When you see this, you instantly know that there is a mistake. What is wrong with the information listed?