The Final Exam will cover material presented in the lectures, with somewhat more emphasis on the material since the midterm. Much of the material is also to be found in the lab manual : Sections 1.4, 1.5, 1.6, 2.2; Appendix A; Appendix B; and Appendix C. After these sample questions, I have listed the major themes of the material since the midterm. Together with the similar list from the midterm review, these constitute a fairly complete summary of the course content you can expect on the final exam.
The final constitutes 100 points (about 10% of the final grade).
The Final will be true/false, multiple choice and short answer format. Below are some sample questions to give you an idea of what to expect.
1. If the siderial time is 20 hours, will an object with a Right Ascension of 16 hours be found east or west of the meridian ?
2. What is the sidereal time on July 21 at 10pm? Could you see a galaxy with coordinates RA=4h 20m Dec=+40 at that time ?
3. At what time of day does third quarter moon rise ?
4. How many degrees separate the sun and moon when the moon's phase is waxing crescent, 3 days past new moon.
5. Describe what precession of the earth's rotation axis is and why it occurs. How does precession affect : the location of the NCP in the sky; the location of the vernal equinox in the sky; the month in which spring occurs; the astrological sign of someone who is born at the end of March.
6. What is the interval of time for a full precession cycle.
7. How many degrees around the equator does the vernal equinox move in a century.
8. (T/F) In precession, the sun and moon slowly pull the earth's equatorial bulge into alignment with the ecliptic.
9. What kind of eclipse does someone in the penumbral shadow of the moon see ?
10. Eclipses can only occur :
11. Why is the moon still visible during a total lunar eclipse ?
12. What is the inclination of the moon's orbit relative to the ecliptic; what are the nodes of the moon's orbit; Why must the moon be at a node for an eclipse to occur ?
13. (T/F) The moon's line of nodes precesses once every 26,000 years.
14. (T/F) Eclipses occur, typically, about every four months.
15. Roughly how often does Mars pass throught the constellation of Orion ?
16. (T/F) Neither venus nor mercury can reach quadrature.
17. An inferior planet has a greatest elongation of 33 degrees. What is its distance to the sun in AU ?
18. (T/F) Mars shows a half phase at Quadrature.
19. You are on Mars. It is martian midnight. You see a planet high in the sky. Which of the following planets could that planet be?
20. (T/F) Venus orbits the sun in about 7 months. If Venus is at greatest eastern elongation in January, then the next time it will be at greatest eastern elongation will be in July.
21. In general, Uranus undergoes retrograde motion twice as often as Neptune.
22. Jupiter is about to reach opposition. Which direction in the sky is it moving ?
23. Why is Saturn so oblate ?
24. (T/F) Blue stars are cooler than green ones.
25. Which of the following properties requires knowing the distance to the star in order to determine that property's value? (a) luminosity, (b) temperature, (c) apparent magnitude, (d) composition
26. A star is at a distance of 5 pc. What is the observed parallax angle?
27. The main sequence represents stars in the H--R diagram that (a) have just finished nuclear burning at the center, (b) are very young stars, (c) are very old stars, (d) have not yet depleted their central hydrogen supply.
28. The axes on an HR diagram are: (a) stellar diameter versus spectral type. (b) wavelength versus frequency. (c) luminosity versus spectral type. (d) intensity of radiation versus wavelength.
29. Nuclear reactions which power the Sun convert (a) a helium nucleus into hydrogen nuclei (b) four hydrogen nuclei into one helium (c) a hydrogen nucleus into a helium nucleus (d) deuterium into hydrogen
30. When the Sun ultimately dies in another 5 billion years it will (a) become a black hole and an X--ray source (b) become a neutron star and a pulsar (c) become a white dwarf with a planetary nebula (d) completely disappear in a supernova explosion
31. The core of a supermassive star is composed of which element if it is about to create a supernova? (a) iron (b) helium (c) neon and magnesium (d) carbon
32. Harlow Shapley determined the direction to the center of the Milky Way by observing the distances and directions to (a) other galaxies (b) HII regions (c) radio-emitting clouds (d) globular clusters
33. 19th century astronomers thought that the Sun was near the center of the Milky Way. The reason that they were not correct is that the galaxy (a) is irregular with a chaotic shape (b) contains dust that obscures distant regions (c) has two kinds of Cepheids and astronomers didn't realize this (d) is cylindrical in shape with the sun near one end so that it appeared to be in the center of a sphere of stars
34. Sketch the Milky Way as seen from edge on, labelling the various components, and indicating a scale in light years. Indicate the sun's position.
35. Why do we think the milky way galaxy is sitting in a huge halo of dark matter?
36. (T/F) For the Australian Aborigines, the group of stars we call Ursa Major (the great bear) is for them a godlike Kangaroo.
37. How many times brighter is the sun (magnitude -26) from the full moon (magnitude -11) ?
38. List the wavebands of electromagnetic radiation, from long wave to short.
39. What is the angular resolution of the Hubble Space Telescope ?
40. How much more light can the HST (primary mirror diameter 2.5 meters) gather than our 8 inch Meade telescopes ?
41. By what factor does the magnification of a telescope increase or decrease when you change a 30mm eyepiece for a 20mm eyepiece. Answer the same question for the field of view.
42. For a reflecting telescope used at the Newtonian focus, how many reflections occur before the image is formed ?
43. How many arcminutes separate the zenith from the Nadir ?
44. What direction (clockwise or counter clockwise) does the diurnal motion take the stars when you look at the North Celestial Pole ? Is this the same when you look at the South Celestial Pole ?
45. What is the difference in altitude of the noon sun between midwinter and midsummer ? Does this depend on your latitude ?
46. What is the hour angle of a star with Right Ascension 3hr 30m at a sidereal time of 6hr ? Approximately when in the year would this sidereal time occur at midnight ?
47. What time of day does a first quarter moon transit ?
49. If the moon orbited the earth in the opposite direction, but with the same period, what would the length of the synodic month be (and, therefore, approximately how many months would there be in the year) ?
Answers can be found here but dont look at them until you have made your own efforts !
Here is a list of the major themes we have discussed in class since the midterm, presented partly in question form. This should give you some idea of the range and scope of the topics.
A. Understand the two sets of coordinates : Right Ascension and Declination as applied to the celestial sphere; and Azimuth and Altitude as applied to the visible sky for an observer. (You should already know the coordinate system for the earth : Longitude and Latitude.) Know the units that these coordinate systems are measured in and where their zero points are.
B. Understand Hour Angle and Siderial time. Hour angle tells you the time until/since an object crosses the meridian, while siderial time tells you what RA is currently on the meridian. Understand the relation between these three quantities : HA = ST - RA. Be able to estimate the Siderial time given the time of day and day of year. Know that 24h of siderial time (ie a siderial day) is 23h 56m of normal (solar) time (ie a normal solar day). Know why these two days have different lengths and why the siderial day is 4 mins shorter than the solar day.
C. Understand and know the names of the phases of the moon. Know how the phase of the moon relates to the angular separation between the moon and sun in the sky. From this know how to estimate where the moon is in the sky from its phase and the time of day.
D. Know the difference between the synodic month and the siderial month and why they are different by about 2.6 days. Know that the orbit of the moon is approximately in the plane of the ecliptic.
E. Understand how the pull of the moon and the sun on the bulge of the earth causes precession --- a 26000 year motion of the earths rotation axis. Know that this causes the NCP to gradually move in a circle of radius 23.5 degrees around the pole of the ecliptic. Thus, the NCP has only recently (last 1000 years) been close to the star Polaris in the sky. Understand that this same motion causes the location of the vernal equinox to move around the ecliptic with the same long period. Realise that this causes the RA and Dec coordinates of a star to change slowly with time, and hence astronomers usually quote the RA and Dec of a star at a reference epoch (usually 1950 or 2000). Realise that this precession also alters where the sun is at a given month (ie season) during the year --- for example, when the astrological rules were being laid down nearly 3000 years ago, the sun was in aries on March 21 (the vernal equinox) so that if you have a birthday at the end of March your sign is Aries. However, today, the vernal equinox has moved about 40 degrees and is now in Pisces, so that on March 21 the sun is in Pisces (soon it will have moved into Aquarius --- the "dawning of the age of Aquarius").
F. Eclipses ! Two types, each ocurring at a particular lunar phase. Recall the structure of shadows cast by extended objects (such as the sun). Know the terms 'umbra' and 'penumbra', and the phenomenon of the 'umbral cone' cast by a spherical object.
G. Know about the THREE types of lunar eclipse. Which one do you hardly notice ? Why is a totally eclipsed moon still visible to us ? Who gets to see a lunar eclipse --- many people or just a few (ie, from where on the earth is a lunar eclipse visible) ? How did the Greeks use lunar eclipses to figure out that the earth was spherical ?
H. Know about the THREE types of solar eclipse. For which one can you see the sun's corona ? Know that because the moon and sun appear the same size in the sky, this means the earth is just about at the tip of the moon's umbral cone. What circumstances lead to an annular eclipse as opposed to a total eclipse ? Approximately what fraction of the earth's surface witnesses a total eclipse/a partial eclipse/no eclipse.
I. Know the moon's orbit is inclined by 5 degrees to the ecliptic plane. What are the 'nodes' of the orbit and why do eclipses only occur when both the moon and the sun are on the 'line of nodes'. Understand why eclipses tend to occur only in "eclipse seasons" approximately twice yearly. Understand the subtlety of the "regression of the line of nodes" which leads to an interval between eclipse seasons of about 5.6 months. Why do the nodes regress ?
J. Understand why the planets are always found near the ecliptic plane. This places them always in zodiac constellations, hence the importance of these constellations for astrology (which, in case i forgot to mention, is rubbish !).
K. Know the various terms : inferior planet, superior planet, conjunction, opposition, quadrature, elongation, greatest elongation. Know how to estimate the distance of an inferior planet to the sun using its greatest elongation. Know the difference between sidereal and synodic periods of planets and know how to calculate one from the other. In general, are synodic periods longer or shorter than sidereal periods ? Know how the phases and brightnesses of planets change during their synodic cycle. Can superior planets show crescent phases ? Why do, for example, Mars and Venus show such large changes in brightness as the months go by ?
L. Understand why planets basically move eastwards with briefer periods of westward (retrograde) motion. Understand why the retrograde motion occurs when the planet is at opposition (for superior planets). How does the length of time spent in retrograde motion depend on how far away the planet is (eg compare the motions of Saturn with Mars) ?
M. What is Albedo and how does it effect a planets brightness. Explain the phenomenon of "The old moon in the new moon's arms". Understand why the Earth, as seen from the moon, is so much brighter than the moon seen from the earth.
N. Know some of the most noticable characteristics of viewing the planets through a small telescope. Venus' phases, high brightness, white color with no features (cloud covered). Mars' reddish (rusty!) color. Know why the summer/winter differences are so much different in the south and the northern hemispheres, leading to big changes in the southern polar ice caps but only modest changes in the north. Why are Jupiter and Saturn not spherical planets ? Why are their moons and rings all orbiting in the equatorial planes ? What is Cassini's division in Saturn's rings and why does it occur ?
O. The properties of stars: Understand the difference between apparent magnitude and absolute magnitude. Why is absolute magnitude a measure of a star's luminosity? How are stellar surface temperatures measured? How do we measure the mass of stars? Know the Mass-Luminosity relation, namely that more massive stars are very much more luminous. Understand that this also means more massive stars die sooner.
P. Know the basic form of the Hertzsprung Russell diagram -- star luminosity (y) plotted against star color (x). Know the three important locations: Main sequence; red giants; white dwarfs.
Q. Know the basic structure of stars and their nuclear reactions. The furnace at the core, surrounded by an intert envelope, ending in the surface which radiates the energy into space. The basic fuel is hydrogen which converts to helium. Why does one need higher temperatures for helium to burn to carbon? Understand how heavier elements up to iron are made by a sequence of nuclear reactions at ever higher temperatures. The overall efficiency of these nuclear reactions is 0.7% compared to full conversion of mass to energy. Know that while hydrogen is burning, the star is on the main sequence, and after that it is a red giant.
R. Understand the two types of stellar death: Low mass stars gently eject their outer envelopes and appear as planetary nebulae. High mass stars explode in supernovae. Either way, the newly made heavy elements are ejected into interstellar space and find their way into new generations of stars. Ultimately, all the matter on earth, and in you, was made inside former generations of stars.
S. Know that the milky way seen in the sky is the disk of our galaxy, seen from within the disk. Understand why the first attempts to find out our position in the disk concluded we were at the center (Herschel and later Kapteyn) -- recall the appearance of LA on a smoggy day. Know about interstellar dust, how it is confined to the disk plane, and how it is less opaque to infrared or radio wavelengths. Know that using globular star clusters gives a better estimate for our location, and shows that we are NOT at the center. Understand how Shapley did this analysis, and used variable stars to derive distances to the globular clusters.
T. Know the components of our galaxy: disk, bulge, nucleus, halo. Understand that the disk is younger and contains ongoing star formation, while the halo globular clusters are extremely old.
U. Understand that modern analysis of galaxy rotation (including the milky way) shows that all galaxies are surrounded by huge halos of dark matter. The visible galaxy is sitting at the "bottom" of the gravitational valley made by the dark matter.