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NAME _________________________________ LAB # ________________

Astronomy 1001/1005 - Final Exam - May 9^th Dr. Henry Lee, Spring 2005

READ THE INSTRUCTIONS CAREFULLY:

The essay questions of this exam may be graded by more than one person, so it is imperative that your name be legibly written on each page of the essay portion!

1. The total points for this exam is 220 points: 45 multiple-choice questions are worth 180 points, and 4 short-answer questions are worth 40 points.

2. Mark the answers you choose on this test as it is your only opportunity to check which answers you got right or wrong. This will not be done for you at a later time in the departmental office. Exams will be available in room 451 Physics during Summer Session TA office hours.

3. Print your NAME and SECTION # on your answer sheet where appropriate. For 1001 students, your SECTION # should read 04. For 1005 students, your SECTION # should read 01. These items are necessary for the proper scoring and computer transfer of your scores.

4. For the multiple-choice questions, use a pencil, and make your marks dark and neat on the answer sheet provided. Erase thoroughly if you wish to change your answer.

5. There is one answer to each multiple-choice question; choose the best answer.

6. When you’re finished, turn in these pages with the questions, the answer sheet provided, and your cribsheet / page of notes.

Multiple Choice (4 points each)

1. Seasonal variations on the Earth are caused by

(a) the ellipticity of Earth’s orbit

(b) variations in the flux coming from the Sun

(d) climate patterns

(e) the melting and freezing of polar ice caps

2. Thermal radiation is defined as radiation

(a) produced by a hot object

(b) that is felt as heat

(d) in the form of emission lines from an object

(e) that depends only on the temperature of the emitting object

3. What is an astronomical unit?

(a) The average distance from the Earth to the Sun

(b) The length of time it takes the Earth to revolve around the Sun

(d) The diameter of the Earth’s orbit around the Sun

(e) Any basic unit used in astronomy

4. Why do we on the Earth essentially see the same face of the Moon at all times? Because the

(a) other face points towards us only at New Moon, when we can’t see the Moon

(b) Moon does not rotate

(d) Moon’s rotational and orbital periods are equal

(e) Moon has a nearly circular orbit around the Earth

5. Which of the following statements correctly describes conservation of energy?

(a) An object always has the same amount of energy

(b) Energy can change between many different forms, but energy is ultimately destroyed

(d) That hydrogen can be fused into helium to produce energy means that helium can also be turned into hydrogen to produce energy

(e) It is not possible for any object to gain or lose potential energy,

6. The motions of stars across the night sky is due to

(a) the gravitational pull of the Moon and the stars

(b) precession

(d) rotation of the Earth on its axis

(e) rotation of the celestial sphere around the Earth

7. From lowest energy to highest energy (highest wavelength to lowest wavelength), which of the following correctly orders the different categories of electromagnetic radiation?

(a) infrared, visible light, ultraviolet, X-rays, gamma-rays, radio

(b) radio, infrared, visible light, ultraviolet, X-rays, gamma-rays

(d) gamma-rays, X-rays, visible light, ultraviolet, infrared, radio

(e) radio, X-rays, visible-light, ultraviolet, infrared, gamma-rays

8. Suppose the angular separation of two stars on the sky is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?

(a) The two stars will look like a single point of light

(b) You will not be able to see the two stars at all

(d) You will see two distinct stars

(e) You will see only the larger of the two stars, not the smaller one

9. Which of the following are relatively unchanged fragments from the early period of planet building in the Solar System?

(a) meteorites (b) asteroids (c) Kuiper belt comets (d) Oort cloud comets (e) all of a-d

10. As the gravity of the outer layers pressing inwards is equal to the pressure set up by the heat generated inside the Sun, we say that our star is in a state of

(a) radiative diffusion

(b) thermal convection

(d) differential rotation

(e) coronal ejection

11. Under what circumstances can differentiation occur in a planet? The planet must

(a) have an atmosphere

(b) be made of both metal and rock

(d) have a molten interior

(e) be geologically active

12. Based on our knowledge of terrestrial planets, what single factor appears to play the most important role in the geological fate of a terrestrial planet?

(a) size of the planet

(b) distance from the Sun

(d) presence of a moon

(e) presence of liquid water

13. The spectrum of the Sun appears as a continuous background of color upon which dark lines are superimposed. This observation means that

(a) most stars are made of a cool, thin gas

(b) light from a dense, hot part of the star passes through a region of even hotter gas

(d) light from a dense, hot part of the star passes through a region of cooler gas

(e) most stars are made of hot, thin gas

14. What is the main reason why the Earth’s carbon dioxide cycle is important?

(a) allows for the continents to grow larger

(b) regulates carbon dioxide concentration and maintains moderate temperatures

(d) prevents humans from suffering any dire consequences from global warming

(e) none of the above

15. Which of the following gases in the Earth’s atmosphere is the best absorber of ultraviolet light?

(a) carbon dioxide (b) nitrogen (c) oxygen (d) water vapor (e) ozone

16. A planet is most likely to have tectonic activity if the planet has

(a) low surface gravity

(b) high surface gravity

(d) high internal temperature

(e) a dense atmosphere

17. The strength of the Coriolis affect depends on the

(a) planet’s distance from the Sun

(b) amount of greenhouse gases in the atmosphere

(d) planet’s temperature

(e) tilt of the planet’s axis

18. Why does the burning of fossil fuels increase the greenhouse effect on Earth?

(a) Burning releases carbon dioxide into the atmosphere

(b) Burning fuel warms the planet

(d) Burning produces infrared light, which is then trapped by existing greenhouse gases

(e) All of the above

19. In what ways is the Earth different from other terrestrial planets?

(a) The lithosphere is broken into plates which move around

(b) There is oxygen in the atmosphere

(d) Life can be found almost everywhere

(e) All of the above

20. Degeneracy is a state of matter that occurs when

(a) the big bang goes through an inflationary stage

(b) thermonuclear reactions halt the contraction of a protostar

(d) magnetic fields slow down motions of charged particles in sunspots

(e) electrons or neutrons inside a star resist being pushed closer together

21. Star clusters are useful for studying stellar evolution because all stars in a cluster have the same

(a) age (b) distance (c) age and distance (d) spectral type (e) luminosity

22. What is the key parameter which determines the evolution and fate of a star?

(a) radius

(b) mass

(d) amount of heavy elements

(e) the environment in which a star is formed

23. In a few billion years, the Sun will become a white dwarf. What will eventually happen to the white dwarf?

(a) becomes a famous show under a different name on the BBC.

(b) shrinks under its own degeneracy pressure and eventually vanishes into nothing

(d) cools and fades over the age of the universe

(e) remains white and hot over the age of the universe

24. What is a standard candle?

(a) An object for which we are likely to know the true luminosity

(b) An object for which we can easily measure the apparent brightness

(d) Any star for which we know the exact apparent brightness

(e) A long, tapered candle that lights easily

25. If the average density of the Universe is larger than some “critical” value, the Universe

(a) will have too many galaxies

(b) will expand forever

(d) is in a steady state

(e) cannot support the fusion of hydrogen into helium

26. Observed rotation curves of disk galaxies do not show the expected drop in velocity as stars get farther from the center of a given galaxy. The conclusion is:

(a) there is much more mass in galaxies than seen in the form of luminous matter

(b) the Universe is expanding

(d) galaxies are formed entirely by spiral density waves

(e) galaxies rotate entirely and only as solid bodies

27. The observed characteristics which identify a quasar are

(a) spiral galaxy appearance, very high spectral blueshift

(b) spiral galaxy appearance, no spectral shift

(d) star-like appearance, very high spectral blueshift

(e) star-like appearance, very high spectral redshift

28. Chemical elements uranium, gold, platinum, and silver are produced in

(a) the core of main-sequence stars

(b) the big bang

(d) supernova explosions

(e) the cores of red giant stars

29. Which of the following astronomical objects or systems is most likely to be the oldest (largest age)?

(a) protostar (b) globular cluster (c) open cluster (d) sun (e) H II region

30. Just before going supernova, what would one expect to find to be most abundant in the very center of the star?

(a) hydrogen (b) helium (c) carbon (d) oxygen (e) iron

31. The Hubble law (distance-velocity) relationship states that

(a) the farther an object is, the faster it appears to be moving away from us, indicating a general overall expansion

(b) all objects appear to have the same velocity away from us, regardless of distance

(d) mutual gravitational attraction of all objects in the universe means that all objects appear to be moving towards us, with the closest ones traveling fastest

(e) all spiral nebulae are located inside our Galaxy

32. Cepheid variable stars are an important “standard candle”, because these stars exhibit a relationship between the star’s average luminosity and

(a) color

(b) position in the galaxy

(d) central nuclear reactions

(e) spectral type

33. The observed differences between stellar spectra are caused primarily by

(a) locations in space

(b) differences in chemical composition

(d) differences in temperature

(e) differences in luminosity

34. Star clusters are useful for studying interstellar evolution because all stars in a cluster have the same

(a) age (b) distance (c) age and distance (d) spectral type (e) luminosity

35. An ionized nebula (H II region) appears red because

(a) it is hot and things which are hot glow red

(b) it is ionized hydrogen which appears red because the brightest emission line is red

(d) it is full of red stars

(e) dust between us and the region blocks blue light, but lets red light through.

36. What characteristic is shared by all stars on the Main Sequence?

(a) They all have the same color index

(b) They are all converting hydrogen into helium in the stellar cores

(d) They all have the same absolute magnitude

(e) They all have planets

37. To what maximum distance can we use the method of stellar parallax to measure the distance of stars?

(a) 5 parsecs (16 light-years) away

(b) 100 parsecs (326 light-years) away

(d) half way across the Milky Way Galaxy

(e) In the Andromeda Galaxy

38. What happens when a star exhausts the hydrogen supply in the core?

(a) The core contracts, but the outer layers expand; the star becomes larger and brighter

(b) The star contracts, becoming smaller and fainter

(d) The star expands, becoming larger and fainter

(e) The core contracts, but the outer layers expand; the star becomes larger but cooler

39. What is the CNO cycle?

(a) Process by which helium is fused into carbon, nitrogen, and oxygen

(b) Process by which carbon is fused into nitrogen and oxygen

(d) Period of a massive star’s life when carbon, nitrogen, and oxygen are fusing into different shells outside the core

(e) Period of a low-mass star’s life when the star can no longer fuse carbon, nitrogen, and oxygen in its core

40. Pulsars (e.g., a pulsar at the heart of the Crab Nebula) are thought to be

(a) accreting white dwarf stars

(b) rapidly rotating neutron stars

(d) unstable high mass stars

(e) accreting black holes

41.Where does most of the present-day star formation occur in the Milky Way galaxy?

(a) in the halo

(b) in the bulge

(d) in the center of the galaxy

(e) uniformly throughout the galaxy

42. After a high-mass star goes supernova, what is left behind as a remnant?

(a) always a white dwarf

(b) always a neutron star

(d) either a white dwarf or a neutron star

(e) either a neutron star or a black hole

43. Which of the following statements is not true about the cosmic microwave background (CMB) radiation?

(a) The CMB has a temperature of about 3 degrees Kelvin above absolute zero.

(b) The CMB is a result of a mixture of radiation from many independent sources, such as stars and galaxies

(d) The CMB was discovered by Penzias and Wilson in the early 1960s.

(e) The CMB appears essentially the same in all directions (the CMB is isotropic).

44. Why do we call dark matter “dark’?

(a) It emits no visible light

(b) We cannot detect the type of radiation emitted

(d) It blocks out the light of stars in a galaxy.

(e) None of the above

45. The estimated age of the Universe is approximately ______________ years.

(a) 12-18 billion (b) 50-100 thousand (c) 1-5 billion (d) 5-20 million (e) 40-50 billion

NAME ________________________________ LAB # ________________

Astronomy 1001/1005 - Final Exam - May 9^th Dr. Henry Lee, Spring 2005

Short Answer (40 points total)

The point value for each individual question in the following section is noted in parentheses next to the question. There are four (4) questions for a total of 40 points. Answer each question clearly and in an organized manner. You do not have to put your answers in the form of complete sentences. Properly labeled diagrams, sketches, and/or bulleted lists are acceptable ways to answer the questions, as long as they clearly convey what you intend to say. Read the questions carefully, and be sure to answer all parts completely.

A (10 points) - Describe what happens during the stages of life for a low-mass star (e.g., a star with the mass of the Sun). Include details of the birth, the various stages over its lifespan, and the eventual fate for a low-mass star.

NAME _______________________________ LAB # ________________

Astronomy 1001/1005 - Final Exam - May 9^th Dr. Henry Lee, Spring 2005

B (10 points) – Although a variety of nebula were known to be Galactic in nature, the

nature of “spiral nebulae” was unclear up until the 20th century. Describe the "controversy" regarding the nature of spiral nebulae, the two key figures in the controversy, and the arguments for the two opposing sides. Describe fully the key observation which removed the controversy, and on which side of the controversy the observation stood.

NAME _______________________________ LAB # ________________

Astronomy 1001/1005 - Final Exam - May 9^th Dr. Henry Lee, Spring 2005

C (10 points) – Describe the “star-gas-star” cycle in the interstellar medium.

NAME _______________________________ LAB # ________________

Astronomy 1001/1005 - Final Exam - May 9^th Dr. Henry Lee, Spring 2005

D (10 points) – List the observed characteristics for spiral galaxies, elliptical galaxies, and irregular galaxies.