Exam 16: A Universe of Galaxies

A) elliptical galaxies are very old and spiral galaxies are very young
B) elliptical galaxies lack anything resembling the disk of a spiral galaxy
C) elliptical galaxies lack anything resembling the halo of a spiral galaxy
D) elliptical galaxies have a spheroidal component (of stars distributed spherically about the galactic center) , and spiral galaxies do not

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A) the fact that elliptical galaxies are more common in clusters of galaxies than outside clusters
B) starbursts
C) the fact that spiral galaxies have both disk and halo components
D) the presence of very large, central dominant galaxies in clusters of galaxies

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A) Bright nuclei were more common long ago, since the light from more distant galaxies has been traveling much longer.
B) Bright nuclei are caused by supermassive black holes surrounded by hot gas.
C) Bright nuclei are more common in cluster galaxies that are farther away.
D) Galaxies appear redder the farther away they are.

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A) a bright source of variable X- ray emission, thought to harbor a supermassive black hole
B) a main- sequence star of spectral type B5
C) a type of galaxy that varies in its light output
D) a type of very luminous star that makes an excellent standard candle

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A) about 30,000 light- years
B) about 900 million light- years
C) about 5000 million light- years
D) about 1400 million light- years

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A) we can watch as they interact in real time
B) we are really smart astronomers
C) the farther away we look, the further back in time we see
D) galaxies are transparent to visible light

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A) main- sequence fitting
B) Hubble's law
C) Cepheid variables
D) Stellar parallax
E) white dwarf supernova

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A) rapid changes in the luminosity of the galaxy nucleus
B) quasars emitting approximately equal power at all wavelengths from infrared to gamma rays
C) the very high speeds of gas orbiting around the galactic nucleus
D) the discovery of powerful jets coming from a compact core
E) all of the above

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A) the distance to the quasar
B) the size of the quasar's central, supermassive black hole
C) the type of host galaxy in which the quasar resides
D) the composition of the quasar

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A) the one that is bluest in color
B) the one that is reddest in color
C) the one that is closest to us
D) the one that is farthest away
E) the one that appears smallest in size

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A) the fact that elliptical galaxies dominate the galaxy populations at the cores of dense clusters of galaxies
B) observations of giant elliptical galaxies at the center of dense clusters that may have grown by consuming other galaxies
C) observations of some elliptical galaxies with stars and gas clouds in their cores that orbit differently from the other stars in the galaxy
D) observations of some elliptical galaxies surrounded by shells of stars that probably formed from stars stripped out of smaller galaxies
E) all of the above

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A) 20 Mly/s
B) 20,000 km/s
C) 0) 20 times the speed of light
D) 50 km/s
E) 20 km/s

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A) It will allow us to determine the mass of the galaxy.
B) Under the rules of the International Astronomical Union, we will be entitled to naming rights for the galaxy.
C) It will allow us to calculate the rotation rate of the galaxy.
D) We can learn the distance to the galaxy.

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A) White dwarf supernovae are much more common than massive star supernovae.
B) We can see only white dwarf supernovae in distant galaxies, not massive star supernovae.
C) White dwarf supernovae follow a period- luminosity relation, while massive supernovae do not.
D) White dwarf supernovae all have roughly the same true peak luminosity, while massive supernovae come in a wide range of peak luminosities.

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A) He applied the period- luminosity relation to Cepheid variables in Andromeda.
B) He measured its parallax.
C) He detected white dwarf supernovae in Andromeda.
D) He applied main- sequence fitting to star clusters in Andromeda.
E) He measured its redshift and applied Hubble's Law.

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A) Radio observations sometimes show long jets of material that can extend millions of light- years out from the galactic center.
B) Spectral lines from the galactic center indicate that clouds of gas are orbiting a central object at very high speed.
C) Infrared observations show that many stars are forming near the centers of active galaxies.
D) The total amount of radiation coming from the galactic center can, in some cases, exceed 100 times the total luminosity of the Milky Way Galaxy.
E) Observed radiation from the galactic center can vary significantly in brightness in times as short as a few days.

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A) we use ultraviolet and X- ray telescopes
B) we have telescopes powerful enough to allow us to identify the spectral types of main- sequence stars of many masses in the cluster
C) the cluster be near enough for us to measure the parallax of its stars
D) we have a well- calibrated period- luminosity relation for Cepheid variable stars

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