ASTRONOMY 101

Mesa College

Spring 2004

Fourth Examination

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

NAME______________________________(Signature) select best answer

1 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.

e. they have irregular light variations because of clouds of carbon particles

high in their atmosphere.

2 Astronomers are able to detect gas, dust and numerous organic molecules between the stars.

a. true b. false

3 A dark appearing cloud in interstellar space is

a. an absorption nebula c. an emission nebula

b. an HII region d. a reflection nebula

4 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

5 The hydrogen in an HII region of space is predominantly

a. ionized c. molecular

b. neutral d. within compounds

6. In 1912 Miss Leavitt discovered that the Cepheids in the Small Magellanic Cloud

a. were all the same brightness

b. obeyed an apparent magnitude/period relation

c. all had the same period

7 21-cm radiation comes about from

a. hot stars ionizing hydrogen gas and setting it aglow

b. an electron dropping to its lowest possible orbit about a hydrogen atom

c. the electron "flipping" up-side-down and spinning the opposite direction in an hydrogen atom

8 The cause of the bluish color in reflection nebulae is

a. neutral hydrogen

b. ionized hydrogen

c. interstellar dust

d. none of the above, reflection nebulae are not blue

9 The principle effect(s) of interstellar dust on starlight is (are)

a. dimming of starlight

b. reddening of starlight

c. both a and b

10 The spiral arms of our galaxy have been traced out and explored by observing

a. globular clusters

b. radio emission from neutral hydrogen(21-cm radiation)

c. O and B stars

d. galactic clusters

e. none of the above

11 A typical star of 1 solar mass, spends the greater part of its life as a

a. pulsar d. red giant

b. planetary nebula e. Cepheid variable

c. main sequence star

12 A star with mass ten or twenty times the sun's mass will probably become, after it is a red giant or supergiant, a

a. proto-star c. nova

b. white dwarf d. supernova

13 A protostar generates its energy by

a. oxidation of carbon

b. fusion of hydrogen into helium

c. fission of uranium

d. conversion of gravitational energy to thermal energy

e. none of the above

14 A star turns off the main sequence when

a. it starts its fusion of hydrogen in the core

b. it starts its fusion of helium in the core

c. it becomes a black hole

d. it begins to run out of hydrogen in its core

15 Place the following objects in increasing order of density.

a. black hole, neutron star, white dwarf

b. neutron star, black hole, white dwarf

c. white dwarf, neutron star, black hole

d. neutron star, white dwarf, black hole

16 Stars on the Main Sequence produce their energy from

a. fusion of carbon into iron c. fusion of He into carbon

b. gravitational energy d. fusion of H into helium

17 If you want to find stars that are being born, where are the best places to search?

a. in HII regions

b. in giant molecular clouds

c. in regions of ultra-hot interstellar gas

d. in the disks around massive stars that were just recently formed

e. Hollywood

18 Which star is the most distant?

a. One having a parallax of 0.02"

b. One having a parallax of 0.20"

c. One having a parallax of 1.00"

19 A parsec is a unit of

a. brightness b. mass c. temperature d. distance

20 The astronomical unit is defined as the

a. average distance between Earth and Sun

b. average distance between Earth and the nearest star

c. diameter of the solar system

d. largest unit of distance used for astronomical measurements

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

a. Associations b. Globular clusters c. Galactic clusters

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

a. emission nebula d. open cluster

b. O star e. dust cloud

c. globular cluster

23 Which of the following more accurately describes open (or galactic) clusters than globular clusters?

a. They have relatively little gas and dust nearby

b. They have stars with more metals in their photospheres

c. They are not concentrated in the plane of the Galaxy

d. They generally are made up of older stars

e. None of the other answers are correct

24 Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made)?

a. they were fused during the supergiant stage in the life of a massive star

b. they were built up from smaller nuclei during a supernova explosion

c. they were fused during the main sequence stage of a low-mass star

d. they were fused deep inside the hot core of the Earth a few million years ago

e. they were produced from other atoms in the cool star envelopes of a red giant star

25 A neutron star is as dense as

a. water c. the center of the earth

b. a white dwarf star d. the nucleus of an atom

26 The conical region, defined for any point on the surface of a collapsed star, through which light can escape is the

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

27 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

28 The order of the stages of evolution a star like our sun goes through is

a. proto-star, white dwarf, main sequence, red giant

b. proto-star, red giant, main sequence, white dwarf

c. proto-star, main sequence, red giant, white dwarf

d. red giant, main sequence, proto-star, white dwarf

e. red giant, white dwarf, main sequence, proto-star

29 A planetary nebula is

a. a proto-planet

b. a shell of gas surrounding a small, hot, dead core of a star

c. a cloud of gas surrounding a pre-main sequence star

d. the name of a bar in Fernwood, Ohio

30 A pulsar can be

a. an unstable red giant. c. the remnant of a supernova event.

b. an unstable white dwarf. d. a nova.

31 The Crab nebula is believed to be the remnant of a

a. nova. b. comet. c. planet. d. supernova.

32 A supernova may give off as much light as the entire galaxy of which it is a part.

a. true b. false

33 Pulsars are assumed to very slowly slow down their spin rates.

a. true b. false

34 A pulsar is an example of a rapidly spinning

a. neutron star b. white dwarf c. Punk band d. black hole

35 What type of telescope did Jocelyn Bell use to discover pulsars in 1968?

a. visible light c. ultraviolet

b. x-ray d. radio

36 According to the general theory of relativity, the presence of mass

a. causes motion at the speed of light squared

b. is equivalent to the presence of light

c. causes curved paths to straighten out until they are exactly straight lines

d. causes a curvature (or warping) if spacetime

37 What is the value of the Chandrasekhar limit?

a. 0.5 solar masses c. 1.4 solar masses

b. 5 solar masses d. 10 solar masses

38 The age of a star cluster can be determined by constructing an H-R diagram of the cluster and then determining its

a. absolute magnitude. c. "turn-off" point.

b. temperature. d. spectral type.

39 A supernova can result when a massive star attempts to fuse iron.

a. true b. false

40 One of the most exciting results from observations of the supernova 1987A was

a. that these observations were the first ever made with a telescope of a supernova in our Galaxy.

b. that it gave the first evidence that supernovae produce heavy elements.

c. that scientists actually detected neutrinos coming from this exploding star.

41 One type of supernova is produced in a binary system when a white dwarf goes over the mass limit of 1.4 by taking mass from its companion giant star.

a. true b. false

42 Which of the following is a prediction of General Relativity?

a. as a mass appears to achieve a speed nearly that of light, its mass appears to increase

b. a light beam will be bent as it passes a massive object

c. for every action there is an opposite and equal reaction

43 The concept that you cannot distinguish between the effects due to gravitation and effects due to the acceleration from other forces or accelerations is known as

a. the general theory of relativity

b. the special theory of relativity

c. the principle of equivalence

d. the inertial law

44 In his General Theory of Relativity, Einstein concluded that in the region near a massive body, as seen by a distant observer,

a. the masses of objects increase

b. clocks tick more rapidly

c. the speed of light increases

d. rulers get longer

e. clocks tick more slowly

45 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

46 Astronomers have looked for planets(and found them) around other stars by

a. resolving them with Earth-based telescopes.

b. resolving them with radio telescopes.

c. attempting to detect the movement (proper motion) of the star around the center of mass of the star-planets system.

Describe how an astronomer, by taking a spectra of a star, can determine its distance. Be sure to mention all the individual steps that are needed. (hint: HR-Diagram) 3 points

Very recently a new technique has been developed to detect planets beyond our solar system

which involves the measurement of radial velocity. Describe this method in detail. 3 points

Describe a nova and how it formed. 2 points

Is your name on the scantron and examination? _______ 1 point