ASTRONOMY 101

Mesa College

FALL 2002

Fourth Examination

NAME______________________________(Print) Lec. hr.______ days class meets______

1 If a star has a parallax of one-sixth of a second of arc, it is at a distance of

a. one-sixth parsec d. one-sixth light years

b. six light years e. 206265 astronomical units

c. six parsecs

2 Cepheid-type variable stars are of considerable interest in astronomy because

a. all are eclipsing binary stars.

b. all are very much like the sun.

c. their period of pulsation is strongly correlated with their average intrinsic

luminosity and therefore astronomers are able to determine their distances.

d. their periods of rotation are all very short, thus they are likely to possess

planetary systems.

3 The general spiral structure of the galaxy has been confirmed by

a. the Doppler effect in starlight from stars in the plane of the Milky Way

b. the distribution of globular clusters in space

c. the distribution of RR Lyrae variables in the plane of the Milky Way

d. 21-centimeter radiation from cold hydrogen gas clouds in space

e. the concentration of dust clouds in certain directions in space

4 In an HII region, the hydrogen is

a. neutral b. ionized c. absent

5 In an HI region, the hydrogen is

a. neutral b. ionized c. absent

6 The interstellar medium is:

a. a fortune teller from another star system.

b. the hydrogen & helium that is within a star.

c. the material that is found in space between galaxies.

d. the dust & gas that is found in the space between stars.

7 21-centimeter radiation from space is produced by

a. an electron transition from the second energy level down to the ground

state of the hydrogen atom

b. the capture of an electron by a hydrogen nucleus

c. collisions between hydrogen atoms in emission nebulae

d. the electron "flipping" up-side-down

8 Which of the following is caused by hot stars ionizing the gas and setting it aglow?

a. reflection nebula b. emission nebula c. absorption nebula

9 A reflection nebula appears to be ________ in color.

a. red b. orange c. blue

10 A dark appearing cloud in interstellar space is

a. an absorption nebula c. an emission nebula

b. an HII region d. a reflection nebula

11 Interstellar reddening is caused by

a. interstellar dust

b. the preponderance of older cooler stars

c. atmospheric absorption

12 The main source of energy for a protostar is

a. gravitational c. chemical

b. comets fall onto its surface d. nuclear fusion

13 Which is true of open clusters?

a. They are associated with dust and gas.

b. They contain old stars.

c. They are found in the halo of the galaxy.

14 Of the following, which has the greatest number of stars.

a. Associations b. Globular clusters c. Galactic clusters

15 Of the following, which has the fewest number of stars.

a. Associations b. Globular clusters c. Galactic clusters

16 In the following list, the type of object most likely to be found in the halo of the galaxy

a. emission nebulas d. open clusters

b. O stars e. dust clouds

c. globular clusters

17 Stars move off the Main Sequence when they

a.. use up all their helium during the giant phase

b. explode in a great supernova explosion

c. just before they become white dwarf stars

d. have used up the their hydrogen fuel in the core

18 During most of a star's evolution, the star lies on the_________ of the H-R diagram.

a. red giant branch b. main sequence c. white dwarf branch d. nova stage

19 The fusion of helium to carbon occurs in what type of star?

a. Main sequence star c. Pre-main sequence star

b. Red giant d. Planetary nebula

20 A planetary nebula represents the transition between what two stages of a star?

a. Red giant and supernova

b. Proto-star and red giant

c. red giant and white dwarf

d. main sequence and cepheid variable

e. proto-star and main sequence

21 A supernova can result when a massive star attempts to fuse helium.

a. true b. false

22 The term "nova" means new. A nova is usually associated with

a. protostars. c. older stars in a binary system.

b. main sequence stars. d. black holes.

23 The Chandrasekhar limit implies that stars ending up with more mass than 1.4 solar masses cannot become

a. supernovae b. giant stars c. neutron stars d. white dwarfs e. black holes

24 A neutron star is typically the diameter of

a. Mercury's orbit d. the sun

b. the Earth e. the Earth's orbit

c. a large city

25 White dwarfs typically are about as

a. luminous as the sun

b. large as the orbit of mercury

c. massive as our moon

d. large as the Earth (in diameter)

e. cool as the coolest main sequence stars

26 Which choice has the objects ranked by diameter, largest to smallest?

a. Red giant, sun, white dwarf, neutron star

b. Red giant, white dwarf, sun, neutron star

c. Red giant, sun, neutron star, white dwarf

d. Sun, red giant, black hole, neutron star

27 A supernova may give off as much light as the entire galaxy.

a. true b. false

28 Because of the large mass of the sun, the ___________ predicts ________________.

a. law of reflection, advance of Mercury's perihelion

b. special theory of relativity, deflection of starlight

c. special theory of relativity, precession of Mercury

d. law of reflection, deflection of starlight

e. general theory of relativity, deflection of starlight

29 Einstein's general theory of relativity attributes the phenomenon called gravity to

a. expansion of the universe

b. rotation of the universe

c. acceleration of the universe

d. curvature of the geometry of space-time

e. none of the above

30 The general theory of relativity predicts that light should be red shifted when leaving a strong gravitational field(warping of space-time).

a. true b. false

31 Imagine yourself in a windowless elevator. What experiment could you perform which would tell you whether you were resting on the surface of a planet in a gravitational field, or in space and accelerating upward at a constant rate?

a. Balls and other objects will fall to the floor, only if you are in a gravitational field.

b. There is no experiment which will tell the difference.

c. The period of a simple pendulum will depend on the length of the pendulum, only if you are in a gravitational field.

d. The apparent path of light will be a curve (the path will appear bent) only if you are in the accelerating elevator.

32 The spectra of white dwarfs usually show red shifts. This is because:

a. Most white dwarfs are moving away from us

b. Their large surface gravities (large masses and small sizes) curve space-time so that the light which they give off is gravitationally redshifted.

c. They are usually rotating fairly fast.

d. Their surface temperatures get lower with time, which makes the light which they give off look redder.

33 The final mass of a star that becomes a black hole has to be

a. between 1.4 and 3 times the mass of the sun

b. less than 1.4 times the mass of the sun

c. greater than 3 times the mass of the sun

34 A pulsar is an example of a

a. neutron star c. white dwarf

b. Punk band d. black hole

35 Which of the following methods can be used to detect the existence of a black hole?

a. observe the visible light emitted

b. analyze the radar echoes

c. radio interferometry

d. observe the gravitational influence it has on a nearby companion

36 The spherical surface around a black hole from within which no radiation or matter can escape is the

a. event horizon b. exit cone c. photon sphere d. singularity point

37 Which of the following is(are) the most likely location(s) of protostar formation?

a. globular clusters c. center of Galaxy(free of dust & gas)

b. molecular clouds d. all of the above

38 The Crab nebula was produced by a

a. planetary nebula. b. nova. c. supernova.

39 Pulsars are known to have their spin rates become slower over time.

a. true b. false

40 The most massive main sequence stars belong to spectral types

a. G and K b. K and M c. O and M d. B and K e. O and B

41 No supernovae have been observed in our galaxy since the 1600's.

a. true b. false

Stars in globular clusters started out with 75% hydrogen. They now contain a much lower percentage of hydrogen. What happened to the hydrogen? 2 points

Describe how the study of a star's spectra can lead to the determination of its distance.

Be sure to give all the important steps. (hint: H-R Diagram) 3 points

Describe the major differences(2) between a nova and a supernova. 2 points

What is the cause of the absorption in an absorption nebula in a telescope? 2 points

Describe how an astronomer would determine the distance to the Andromeda Galaxy by using observations of Cepheid variable stars. Be sure to include all steps. 3 points

What is the difference in the appearance between the HR diagram of a cluster of young stars compared to a cluster of old stars? 2 points

What is it that determines if a star becomes a neutron star or a white dwarf? 2 points

What type of stars produce the heaviest elements? 2 points

Describe in detail that part of the life cycle of the Sun from the main sequence to the black dwarf stage. Be sure to discuss sources of energy and changes in diameter during this period of time.

3 points

Describe the properties of a black dwarf. (3 things) 3 points

Describe the appearance of a globular cluster appears in a telescope. State at least two observable aspects. 2 points

Describe degenerate matter. 2 points

Give the six stages in the life of the Sun, including pre-birth. 6 points

(Use astronomical terminology.)

1. _____________________________________________

2. _____________________________________________

3. _____________________________________________

4. _____________________________________________

5. _____________________________________________

6. _____________________________________________

What is the difference in the appearance between the HR diagram of a cluster of young stars compared to a cluster of old stars? 2 points

How does a white dwarf star differ from a neutron star. (Three major differences. Describe the differences.) 3 points

Suppose you have discovered a new star cluster. How would you go about determining whether it is an open or globular cluster? State two things 2 points

Describe how astronomers go about discovering new extra-solar planets by observing the proper motions of stars. 2 points