PH109 Exploring the Universe Test #3, Fall 2008

PH109 Exploring the Universe Test #3, Fall 2008

Please indicate the best answer to the following questions on the answer sheet provided.

1) If the Sun were replaced by a black hole having one solar mass, what would happen to the Earth's orbit?

a. the Earth would spiral inward b. the Earth would jump to a smaller orbit

c. the size of the Earth's orbit would increase rapidly d. the Earth's orbit would remain the same

2) A neutron star is expected to spin rapidly because

a. they conserved angular momentum when they collapsed. b. they have high orbital velocities.

c. they have high densities. d. they have high temperatures.

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

a)Absolute brightness., b) Where it was born., c) Surface temperature., d) Mass.

4) Sunspots appear dark because

a) they are cooler regions, b) they are concentrations of carbon,

c) their spectrum has been Doppler shifted, d) impurities in the Sun

5) Which of the following nuclear fuels does a one solar mass star use over the course of its entire evolution?

a. hydrogen, b. hydrogen and helium, c. hydrogen, helium and carbon

d. hydrogen, helium, carbon, and neon, e. hydrogen, helium, carbon, neon, and oxygen.

6) What will be the last element that the Sun will be able to "burn"

a) Hydrogen, b. Helium, c. Carbon, d. Oxygen

7) Red stars are _____ than blue stars

a. hotter b. cooler c. larger d. smaller

8) About how old is our Sun?

a) 10 million years b. 5 billion years c. 10 billion years d. 1 million years

9) How much more time does our Sun have to remain on the main sequence?

a) 10 million years b. 5 billion years c. 10 billion years d. 1 million years

10) Which star are guaranteed to be less than 20 million years old?

a. O, b. B, c. M, d. G

11) The primary reason for the 22 year sunspot cycle is

a) Orbit of Jupiter, b. Alignment of the planets every 22 years.

c) magnetic field reversal d. enhanced synchrotron radiation

12) The spectral type of a star measures its:

a) luminosity. , b) chemical composition. , c) size. , d) temperature. , e) mass

13) The H-R diagram can plot:

a) temperature versus mass. , b) radius versus luminosity. , c) temperature versus luminosity.

d) apparent magnitude versus spectral classes.

14) Some regions along the plane of the Milky Way appear dark because:

a) there are no stars in these areas. , b) stars in that region are hidden by interstellar gas.

c) stars in that region are hidden by dark dust particles. , d) many brown dwarfs in those areas absorb light.

15) Sunspots usually occur

a) as single regions, b. in pairs,

c) in groups of three or more, d. as continuous regions around the sun's equator

16) Which of the following stars is most dense?

a. a supergiant star, b. a main sequence star, c. a giant star, d. a white dwarf

17) Synchrotron radiation is produced by

a) objects with temperature below 10,000 K.

b) high-velocity electrons moving through a magnetic field.

c) cold hydrogen atoms in space.

d) the collapsing cores of massive stars.

18) Which event marks the birth of a star?

a) Fusion of hydrogen atoms into helium atoms., b) Collapse of an interstellar cloud.

c) Formation of a photosphere., d) a card in the mail.

19) The observed slowing of a clock in the vicinity of a black hole is a prediction of:

a) Special relativity, b) General relativity,

c) Stellar nucleosynthesis, d) The Principle of Cosmic Censorship.

20) What explanation does general relativity provide for gravity?

a) Gravity is a result of curved spacetime., b) Gravity is directly proportional to mass.

c) Gravity is inversely proportional to radius., d) Gravity is stronger the faster you go.

21) What is curious about jets.

a) that they exist. b) that they remain collimated over large distances,

b) that there are two of them, d) that you have to wait in the airport longer than the flight is

22) The first extraterrestrial planets were fond

a) by the Hubble Space Telescope, b) by radio astronomers,

c) by X-ray astronomers, d) by infrared astronomers.

23) In the twin paradox

a) we explain how identical twins can behave so differently, b) the faster twin lives longer,

c) the stay at home twin lives longer, d) they age the same.

24) Helioseiemologists

a) marry more than one spouse, b) created the heliocentric model of the solar system,

c) study Sun induced Earthquakes, d) study the ringing Sun.

25) If two star s in the same star cluster appear to have the same brightness they

a) have the same luminosity, b) they are the same distance away,

c) they have the same spectral type, d) can’t tell.

26) A star which is discovered to be a binary system on the basis of the Doppler shifts of the spectral lines of its two stars is called a

a) spectroscopic binary, (b) astrometric binary, (c) visual binary, (d) eclipsing binary

27) The centers of solar granules

a) are hot material rising to the photosphere from below.

b) are cool material falling from the photosphere to the regions below.

c) are fainter and hotter than their surroundings.

d) are brighter and cooler than their surroundings.

28) A star's luminosity depends only on the star's

a. distance and diameter, b. temperature and distance,

c) distance. d. temperature and diameter

29) We know that giant stars are larger in diameter than the sun because

a) they are more luminous but have about the same temperature.

b) they are less luminous but have about the same temperature.

c) they are hotter but have about the same luminosity.

d) they are cooler but have about the same luminosity.

30) Pulsars give off mostly which kind of radiation

a) positronic b. spinar c. synchrotron d. circumstellar

31) The fact that convection is occurring in the outer layers of the Sun is demonstrated by

a) solar eruptions, b. sunspots, c. granules, d. solar wind

32) The two most abundant elements in the sun are

a) nitrogen and oxygen, b. hydrogen and helium,

c) sulfur and iron, d. carbon and hydrogen

33) You are standing near a railroad track and a train is moving toward you at 60 mph and blowing its horn. What will you notice as the train moves past you?

a) As the train approaches, the horn will sound lower in pitch than when it is moving away.

b) As the train approaches, the horn will sound higher in pitch than when it is moving away.

c) There will be no change in the pitch of the horn as it moves by.

d) The horn will get louder as the train moves away from you.

34) Most of the light we see coming from the sun originates in the

a) chromospheres, b. photosphere, c. coronad) sunspots

35) What causes the outward pressure that balances the inward pull of gravity in a star?

a) The outward flow of energy. b. The opacity of the gas.

c) The temperature of the gas d. The density of the gas

36) A ______is a city sized star supported by degenerate neutrons.

a) super novae, b) white dwarf, c) neutron star, d) pulsar

37) If we counted all the stars currently on the main sequence, which spectral type would be most abundant?

a) A, b) B, c) K, d) M

38) What mechanism is most responsible for the twisting of the Sun's magnetic field lines?

a) differential rotation, b. convection, c. proton-proton cycle, d. tidal force

39) Sunspots are dark because

a) regions of the photosphere are obscured by material in the chromospheres.

b) shock waves move through the photosphere.

c) the sun rotates differentially.

d) the strong magnetic field inhibits the currents of hot gas rising from below.

40) The correct order of spectral class sequence is:

a) BOAGFM, b) OBAFGKM, c) MKGAFBO, d) FOBMGKA