WSU ASTR 135 Exam 2

10-28-98

a. establishes the butterfly diagram

b. allows astronomers to predict climatic changes on Earth

c. has led astronomers to conclude that Sun is very gradually cooling off

d. is referred to as the Zeeman effect

2. Evidence that sunspots are sites of intense magnetic fields:

a. evidence of the Zeeman effect in spectra of sunspot regions

b. the dynamo effect

c. the Maunder butterfly diagram

d. none of the above. Sunspots are holes in the chromosphere, not sites of magnetic fields

3. The Babcock model explains the solar magnetic cycle as due to

a. bursts of solar wind particles produced by solar flares

b. helioseismology

c. the differential rotation and magnetic field of the Sun

d. coronal holes

4. When you observe Sun in the sky with your eyes, you are looking at the

a. corona

b. chromosphere

c. photosphere

d. spicules

5. The rotation of Sun is determined by

a. observing the locations of sunspots from day to day

b. using the Zeeman effect

c. observing the dynamo effect

d. none of the above. Sun does not rotate

6. For main sequence stars, the general rule is: the higher the surface temperature,

a. the more numerous are the stars

b. the greater the masses of the stars

c. the less luminous are the stars

d. the more common are binary stars

7. Which of the following does a star's spectrum NOT tell us about that star?

a. Its apparent visual magnitude

b. Its chemical composition

c. Its motion relative to Earth

d. Its luminosity class

8. If two observations of the stars Sirius and Arcturus are made at 6

month intervals, Sirius reveals a greater parallax because Sirius is

a. closer to us than Arcturus

b. hotter than Arcturus

c. more massive than Arcturus

d. more distant than Arcturus.

9. In order to detect an eclipsing binary star system, astronomers

a. obtain the spectrum of the system

b. determine the trigonometric parallax of the system

c. identify the two stars as a visual binary system

d. graph the brightness of the system with respect to time

10. You look through a telescope and observe a nebula with a slight bluish color. It

a. is a cloud of hot hydrogen

b. is an O- or B-type of cloud

c. would reveal a continuous spectrum if a spectrum were obtained of it

d. is a cloud of dust

11. As a protostar collapses in the process of becoming a star, its internal temperature increases due to

a. gravitational energy converted to thermal energy

b. nuclear fusion

c. atoms colliding with one another and breaking apart (nuclear fission)

d. the CNO cycle

12. The more massive a protostar that collapses to become a star

a. the faster it reaches the main sequence stage

b. the lower its temperature will be as a main sequence star

c. the longer its main sequence lifetime will be

d. the less luminous it will be as a main sequence star

13. Why is it that a star like Sun leaves the main sequence toward stellar death?

a. Because all of the hydrogen within the star is eventually

consumed, and turned into helium

b. The helium flash causes the star to expand and get cooler, moving upward on the H-R diagram

c. Accumulation of helium in a star's core shuts down the proton-proton chain

d. A shock wave from a supernova sets off the star toward death

14. What is it that prevents a particular dying star from collapsing past the white dwarf stage?

a. Neutrinos emitted by the explosion that creates the white dwarf push outward

b. Degenerate electrons resist further compression

c. The helium flash pushes the star outward

d. The carbon detonation event pushes the star outward

15. Which of the following stages of stellar death will Sun go through after red giant stage but before white dwarf stage?

a. Pulsar

b. Neutron star

c. Supernova

d. Planetary nebula

16. Black holes are most easily identified

a. when their effect on a nearby star can be observed

b. by looking for locations in the sky where it is particularly dark

c. with the largest optical telescopes on Earth

d. when Earth is lined up along the magnetic axis of the black hole

17. In order to know for certain that an object is a black hole, astronomers must first

a. observe a circular black disc in the sky

b. detect pulses of radiation coming from the event horizon. This is called the lighthouse effect

c. detect glitches in the radiation emitted by the black hole

d. determine the mass of the compact object suspected of being the black hole

18. The Schwarzschild radius is associated with

a. the maximum size possible for a white dwarf star

b. the size of the cone of radiation emitted by pulsars

c. a nebula whose size allows it to eventually collapse to become a star

d. the size of the event horizon of a black hole

19. By what mechanism does radiation reach the Sun's surface from its interior?

a. ionization

b. neutrons

c. convection

d. solar wind

20. What is the natural barrier making it difficult for two protons to stick together?

a. antigravity

b. electric repulsion

c. no barrier exists

d. strong force

21. Which of the following apparent magnitudes is the brightest?

a. 5.0

b. 15.8

c. 3.2

d. -1.1

22. The absolute magnitude of a star is what the apparent magnitude of the star would be if seen at what distance?

a. 10 parsecs

b. 100 lightyears

c. 10 lightyears

d. 100 parsecs

23. What two properties are used to classify a star?

a. Luminosity and surface temperature

b. Distance and luminosity

c. Distance and surface temperature

d. Distance and color

24. Which of the following is the most common type of star?

a. white dwarf

b. red giant

c. main sequence stars

d. supergiants

25. What is the single most important characteristic in determining the course of a star's evolution?

a. apparent brightness

b. distance

c. color

d. mass

26. Why are star clusters good for stellar evolution studies?

a. The combined light of the stars makes them easier to see.

b. Star clusters are always located in the plane of the galaxy.

c. Stars in clusters began forming at the same time, have similar starting composition, and are at about the same distance away.

d. Stars in clusters are always very young and shine brightly.

27. The interstellar gas is composed mainly of:

a. hydrogen and helium

b. carbon

c. ammonia, methane, and water

d. iron

28. What effect does dust have on visible light passing through it?

a. It dims and reddens it.

b. It completely blocks all visible light from passing through.

c. All light is turned a bluish color.

d. It has no effect on light.

29. For gravity to contract a spinning interstellar cloud, there needs to be sufficient

a. heat

b. mass

c. magnetism

d. rotation

30. What happens when an interstellar cloud shrinks?

a. density rises

b. temperature rises

c. internal pressure increases

d. all of the above

e. none of the above

31. What defines a main-sequence star?

a. rapid rotation and strong stellar winds

b. fusion of hydrogen into helium in the core

c. the surface temperature

d. the apparent brightness

32. The proton-proton chain needs a temperature of

a. 10 K

b. 100 K

c. 10,000 K

d. 10⁷ K

33. All stars must eventually leave the main-sequence because

a. they use up the hydrogen in their cores.

b. they use up the helium in their cores.

c. they use up the iron in their cores.

d. gravity weakens over time.

34. What is a planetary nebula?

a. A planet surrounded by a glowing shell of gas.

b. The disc of gas and dust around a young star.

c. The ejected envelope of a red giant surrounding a stellar core remnant.

d. A young medium mass star.

35. A star lasts the longest as a

a. protostar

b. supernova

c. red giant

d. main-sequence star

36. Just before a star explodes as a supernova, its core has turned into:

a. carbon

b. water

c. iron

d. helium

37. The Roche lobe of a star in a binary system

a. resembles the ear of Edouard Roche, the French mathematician.

b. is the star's gravitational zone of influence.

c. is the disc that will form planets.

d. is the an accretion disc around the companion star.

38. On the H-R diagram of a star cluster, what is used to determine the age of the cluster?

a. The number of red giants.

b. The number of faintest stars.

c. The main-sequence turnoff.

d. The total number of stars in the cluster.

39. A surface explosion on a white dwarf, caused by infalling material from a binary companion star is what kind of object?

a. nova

b. type-I supernova

c. type-II supernova

d. contact binary

40. An iron core cannot support a star because:

a. iron rusts

b. iron cannot fuse with other nuclei to produce energy

c. iron supplies too much pressure

d. iron is too heavy

41. A star can be a supernova

a. many times

b. at various times, depending on the mass

c. once

d. just twice

42. What is the approximate amount of time it takes for a stellar iron core to collapse?

a. one second

b. one day

c. one year

d. 200,000 years

43. A neutron star has a size of about

a. 10 cm

b. 20 km

c. 6000 km

d. 1 AU

44. The granulated appearance of the Sun is evidence for

a. aurora

b. dynamo effect

c. convection

d. flares

45. Apparent magnitude depends on

a. H-R diagram and temperature

b. luminosity and distance

c. giant stars and white dwarfs

d. visual and spectroscopic binaries

46. The laws of stellar structure are

a. the period squared is equal to the distance cubed.

b. conservation of gravity, conservation of dynamics, and mass transport.

c. special relativity, general relativity, and string theory.

d. conservation of mass, conservation of energy, hydrostatic equilibrium, and energy transport.

47. The behavior of a degenerate gas is

a. no expansion with increasing temperature.

b. contraction with increasing temperature.

c. expansion with increasing temperature.

d. increase in pressure with time.

48. The escape velocity at the event horizon of a black hole is

a. 100 m/sec

b. 1000 m/sec

c. the speed of light

d. twice the speed of light

49. The more massive a main-sequence star:

a. the hotter its surface temperature

b. the hotter its core temperature

c. the more rapidly the star evolves

d. all of the above

e. none of the above

50. In the proton-proton chain:

a. 4 neutrinos are converted into 2 protons + energy

b. 4 protons are converted into one helium + energy

c. 6 protons are converted into carbon but takes energy

d. 3 helium are converted into carbon + energy