NAME _____________________________ ID # ______________ LAB # ________

Astronomy 1001 - Midterm #2 Dr. Leonard Kuhi - Spring 2000

Read Instructions Carefully:

The essay questions of this exam are graded by more than one person, so it is imperative

that your NAME BE LEGIBLY WRITTEN ON EACH PAGE OF THE ESSAY

PORTION!

1. 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 returned to the alphabetical boxes in the North wall of the Physics

building approximately 3-4 days after the exam.

2. Print your NAME, ID # and SECTION # on your answer sheet where appropriate. Your

SECTION # should read 02. All three items are necessary for the proper scoring and

computer transfer of your scores.

3. Use a pencil, make your marks dark and neat, and erase thoroughly.

4. There is only one answer to each question. Choose the best answer.

5. You may use one sheet of notes and you may use this test for scratch paper.

I. Multiple Choice (3 pts. each)

1. Which of the following statements about X-rays and radio waves is not true?

a) X-rays have shorter wavelengths than radio waves

b) X-rays and radio waves are both forms of light, or electromagnetic radiation

c) X-rays have higher frequency than radio waves

d) X-rays have higher energy than radio waves

e) X-rays travel through space faster than radio waves

2. If you heat a gas so that collisions are continually bumping electrons to higher energy levels,

when the electrons fall back to lower energy levels the gas produces

a) thermal radiation

b) an absorption line spectrum

c) an emission line spectrum

d) x-rays

e) radio waves

3. From laboratory measurements, we know that particular spectral line formed by hydrogen

appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the

same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?

a) the star is moving toward us

b) the star is moving away from us

c) the star is getting hotter

d) the star is getting colder

e) the "star" actually is a planet

4. If the Moon is setting at noon, the phase of the Moon must be

a) full b) first quarter c) third quarter d) waning crescent e) waxing crescent

5. When white light passes through a cool cloud of gas, we see

a) visible light

b) infrared light

c) thermal radiation

d) an absorption line spectrum

e) an emission line spectrum

6. Which of the following describes impact cratering?

a) the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface

b) the eruption of molten rock from a planet's interior to its surface

c) the disruption of a planet's surface by internal stresses

d) the wearing down or building up of geological features by wind, water, ice, and other

phenomena of planetary weather

7. Why isn't there a planet where the asteroid belt is located?

a) there was not enough material in this part of the solar nebula to form a planet

b) a planet once formed here, but it was broken apart by a catastrophic collision

c) gravitational tugs from Jupiter prevented material from collecting together to form a planet

d) there was too much rocky material to form a terrestrial planet, but not enough gaseous material

to form a jovian planet

e) the temperature in this portion of the solar nebula was just right to prevent rock from sticking

together.

8. What characteristic distinguishes a meteorite from a terrestrial rock?

a) a meteorite is usually covered with a dark crust from burning in the Earth's atmosphere

b) a meteorite usually has a high metal content

c) meteorites have different isotope ratios of particular elements when compared to terrestrial

rocks

d) meteorites contain rare elements, such as iridium, that terrestrial rocks do not

e) all of a-d

9 In the asteroid impact theory of the extinction of the dinosaurs some 65 million years ago, the

dinosaurs (and over half of all the other species on the Earth at that time) died off largely because

a) of injuries suffered from direct hits of pieces of the asteroid or comet

b) dust injected into the stratosphere from the impact absorbed visible light from the Sun, causing

global temperatures to plummet

c) radiation from iridium in the asteroid caused the dinosaurs to die of cancer

d) the impact caused massive earthquakes and volcanic activity worldwide

e) dust settled on the leaves of planets, making them inedible, so the animals died of starvation

10. Why does the plasma tail of a comet always point away from the Sun?

a) the solar wind blows the ions directly away from the Sun

b) radiation pressure from the Sun's light pushes the ions away

c) the conservation of the angular momentum of the tail keeps it always pointing away from the

Sun

d) gases from the comet, heated by the Sun, push the tail away from the Sun

e) it is allergic to sunlight

11. At the center of the Sun, fusion converts hydrogen into

a) hydrogen compounds

b) plasma

c) radiation and elements like carbon and nitrogen

d) radioactive elements like uranium and plutonium

e) helium, energy, and neutrinos

12. Earth's atmosphere contains only small amounts of carbon dioxide because

a) the Earth's volcanoes did not outgas as much carbon dioxide as those on Venus and Mars

b) most of the carbon dioxide was lost during the age of bombardment

c) chemical reactions with other gases destroyed the carbon dioxide and replaced it with the

nitrogen that is in the atmosphere now

d) carbon dioxide dissolves in water, and most of it is now contained in the oceans and carbonate

rocks

e) Earth doesn't have as strong a greenhouse effect as is present on Venus

13. Which of the following statements about the greenhouse effect is true?

a) without the naturally occurring greenhouse effect, the Earth would be too cold to have liquid

oceans

b) a weak greenhouse effect operates on Mars

c) the burning of fossil fuels increases the greenhouse effect on Earth because of the release of

carbon dioxide

d) one result of an increased greenhouse effect on Earth may be an increased number of severe

storms

e) all of a-d

14. What do we mean when we say that the Sun is in hydrostatic equilibrium?

a) the hydrogen gas in the Sun is balanced so that it never rises upward or falls downward

b) the Sun maintains a steady temperature

c) this is another way of stating that the Sun generates energy by nuclear fusion

d) there is a balance within the Sun between the outward push of pressure and the inward pull of

gravity

e) the Sun always has the same amount of mass, creating the same gravitational force

15. Which of the following statements about spectral types of stars is true?

a) the spectral type of a star can be used to determine its surface temperature

b) the spectral type of a star can be used to determine its color

c) a star with spectral type A is cooler than a star with spectral type B

d) a star with spectral type F2 is hotter than a star with spectral type F3

e) all of a-d

16. Why do sunspots appear dark in pictures of the Sun?

a) they are too cold to emit any visible light

b) they actually are fairly bright but appear dark against the even brighter background of the

surrounding sun

c) they are holes in the solar surface through which we can see to deeper, darker layers of the sun

d) they are tiny black holes, absorbing all light that hits them

e) they emit light in other wavelengths that we can't see

17. What is granulation in the Sun?

a) the bubbling pattern on the photosphere produced by the underlying convection

b) another name for the way sunspots look on the surface of the Sun

c) elements in the Sun other than hydrogen and helium

d) dust particles in the Sun that haven't been turned into plasma

e) lumps of denser material in the Sun

18. Since all stars begin their lives with the same basic composition, what characteristic most

determines how they will differ?

a) location where they are formed

b) time they are formed

c) luminosity they are formed with

d) mass they are formed with

e) color they are formed with

19. Which of the following statements about an open cluster is true?

a) all stars in the cluster are approximately the same color

b) all stars in the cluster are approximately the same age

c) all stars in the cluster have approximately the same mass

d) all stars in the cluster will evolve similarly

e) there is an approximately equal number of all types of stars in the cluster

20. Which two energy sources can help a star maintain its internal thermal pressure?

a) nuclear fusion and gravitational contraction

b) nuclear fission and gravitational contraction

c) nuclear fusion and nuclear fission

d) chemical reactions and gravitational contraction

e) nuclear fusion and chemical reactions

21. What happens to the core of a star after a planetary nebula occurs?

a) it contracts from a protostar to a main-sequence star

b) it breaks apart in a violent explosion

c) it becomes a white dwarf

d) it becomes a neutron star

e) none of a-d

22. When does a star become a main-sequence star?

a) when the protostar assembles from a molecular cloud

b) the instant when hydrogen fusion first begins in the star's core

c) when the rate of hydrogen fusion within the star's core is high enough to sustain hydrostatic

equilibrium

d) when a star becomes luminous enough to emit thermal radiation

e) when hydrogen fusion is occurring throughout a star's interior

23. Why does a star grow larger after it exhausts its core hydrogen?

a) the outer layers of the star are no longer gravitationally attracted to the core

b) hydrogen fusion in a shell outside the core generates enough thermal pressure to push the

upper layers outward

c) helium fusion in the core generates enough thermal pressure to push the upper layers outward

d) helium fusion in a shell outside the core generates enough thermal pressure to push the upper

layers outward

e) the internal radiation generated by the hydrogen fusion in the core has heated the outer layers

enough that they can expand after the star is no longer fusing hydrogen

24. What happens when the gravity of a massive star is able to overcome neutron degeneracy

pressure?

a) the core contracts and becomes a white dwarf

b) the core contracts and becomes a ball of neutrons

c) the core contracts and becomes a black hole

d) the star explodes violently, leaving nothing behind

e) gravity is not able to overcome neutron degeneracy pressure

25. Which event marks the beginning of a supernova?

a) the onset of helium burning after a helium flash in a star with mass comparable to that of the

Sun

b) the sudden outpouring of X-rays from a newly formed accretion disk

c) the sudden collapse of an iron core into a compact ball of neutrons

d) the beginning of neon burning in an extremely massive star

e) the expansion of a low-mass star into a red giant

NAME ____________________________________ ID # ___________________

Section 2 - Midterm #2 Dr. Leonard V. Kuhi - Spring 2000

Essay Total: ___________

II. Short Answer

1) Give two examples of tidal effects in the solar system (not the moon and the Earth).

Explain what is happening or has happened in each case. (25 pts.)

2) What is the solar neutrino problem? What explanations have been given to solve the

problem? Which is most likely? Why?

NAME ____________________________________ ID # ___________________

Section 2 - Midterm #2 Dr. Leonard V. Kuhi - Spring 2000

3) Sketch an HR diagram for a very old cluster. Label the axes and key parts of the

diagram. What feature of the diagram indicates that the cluster is very old? Explain.

4) Suppose that the star Betelgeuse ( a bright red supergiant in Orion) were to become a

supernova tomorrow (as seen from Earth). What would it look like to the naked eye? Explain