Download Question 1 The star Regulus, in the constellation Leo, appears

Question 1
. The star Regulus, in the constellation Leo, appears brighter through a blue filter than
it does through a yellow filter. Suppose that a second star is found that has the
same brightness as Regulus through the blue filter but is brighter than Regulus
through the yellow filter. From this information, we can say conclusively that the
second star has .
. 1. a higher temperature.
.
.
. 2. a lower temperature.
.
.
. 3. the same temperature but a higher luminosity.
.
.
. 4. the same temperature but a lower luminosity.
.
. 1 points
Question 2
. Light leaving a point source spreads out so that the apparent brightness I of light per
unit area varies with distance d according to which of the following laws (∝ means
“proportional to”)?
.
.
.
.
. 1. I ∝ 1/d2
.
. 2. I = constant
.
. 3. I ∝ d2
.
. 4. I ∝ 1/d
.
. 1 points
Question 3
. Which of the following observations would NOT be an indication of a binary star
system? .
. 1. A “star” image periodically separates into two distinct images and then blends again.
.
.
. 2. The “star” appears to move in a straight line against a background field of stars.
.
.
. 3. A “star” appears to become periodically dimmer and then brighter for a few hours at a time.
.
.
. 4. The “star” appears to wiggle in its path across Earth's sky against the background stars.
.
. 1 points
Question 4
. The relative brightness of a star as we see it in Earth's sky is called .
. 1. surface temperature.
.
.
. 2. absolute magnitude.
.
.
. 3. luminosity.
.
.
. 4. apparent magnitude.
.
. 1 points
Question 5
. How bright (in absolute magnitude) are the intrinsically faintest stars in the universe?
.
. 1. +
. 1
7
.
. 2. 0
.
.
. 3. –
. 1
0
.
. 4. +
. 1
. 1 points
Question 6
. What is spectroscopic parallax? .
. 1. apparent change in position of a nearby star compared with distant background
. stars
. due to the motion of Earth around the Sun
.
.
. 2. change in position of the absorption lines in a star's spectrum due to the Doppler
. shift
. caused by the star's motion around the center of mass in a binary star system
.
.
. 3. distance to a star measured using the spectral luminosity class of the star and the
. inverse
.
square law
.
.
. 4. apparent change in position of the absorption lines in a star's spectrum due to the
. Doppler
.
shift caused by Earth's motion around the Sun
. 1 points
Question 7
. Two stars whose apparent magnitudes differ from each other by five magnitudes
have a ratio of brightnesses of .
. 1. 1
. 0
.
.
. 2. 2
. 5
.
.
. 3. 2
. .
5
.
.
. 4. 1
. 0
0
.
. 1 points
Question 8
. A white dwarf star whose temperature is the same as that of the Sun will have a
radius that is (see Fig. 11-8, Comins and Kaufmann, Discovering the Universe, 8th
Ed.)
.
. 1. the same size as the Sun's.
.
.
. 2. 100 times smaller than that of the Sun.
.
.
.
. 3. 10 times smaller than that of the Sun.
.
. 4. 2 times smaller than that of the Sun.
.
. 1 points
Question 9
. Stellar parallax appears because .
. 1. Earth rotates about its own axis.
.
.
. 2. stars have finite size (i.e., they are not really just points of light).
.
.
. 3. stars move in space.
.
.
. 4. Earth moves in space.
.
. 1 points
Question 10
. We are about 8000 parsecs from the center of the Milky Way Galaxy, and the smallest
parallax angle we can measure from orbiting observatories is about 0.001
arcseconds. How far toward the galactic center can we see with this technique
(ignoring galactic dust and other obstacles)? .
. 1. only 0.008 = 1/125 of the way to the center
.
.
. 2. about 1/8 of the way to the center
.
.
. 3. all the way to the center
.
.
. 4. about halfway to the center
.
Question 11
. Which statement best describes the “fabric” of space and time as outlined by the
classical physics of Newton?
.
. 1. Space is expanding uniformly, while time passes more slowly as the universe ages.
.
.
. 2. Space is perfectly uniform, filling everywhere like a fixed network, while time passes
. at a. uniform rate for all observers.
.
.
. 3. Space becomes “curved” and time slows down near a source of gravity, as measured
. by .a distant observer.
.
.
. 4. The shape of space and the rate of passage of time depend on the relative velocities
. of observer
.
and observed.
. 1 points
Question 12
. In the context of black holes, the word ergosphere names the
.
. 1. entire region inside the event horizon.
.
.
. 2. region just outside the event horizon of a rotating black hole where it is impossible
.
.
.
.
. 3.
.
.
. 4.
for .anything to remain at rest.
region occupied by the accretion disk where matter from a companion star collects
around
.
a black hole.
entire universe outside the black hole.
.
. 1 points
Question 13
. What method is used by astronomers to infer the existence in space of a dark object
of about 5 solar masses, such as a black hole? .
. 1. estimation of the luminosity of the object and the application of the
. mass-luminosity
.
relationship
.
.
. 2. measurement of the effect of its gravitational force on a companion
. object
. in a binary system
.
.
. 3. infrared imaging of a region whose effective temperature is lower than
. the. cosmic microwave background, rendering it dark
.
.
. 4. measurement of the gravitational redshift of spectral lines in the spectrum
. of the
. object
. 1 points
Question 14
. A black hole is so named because .
. 1. the gravitational field is so high that the wavelength of its emitted light
. is gravitationally
.
redshifted to radio wavelengths.
.
.
. 2. no light can escape from it due to its powerful gravitational field.
.
.
. 3. it emits no visible light because it is so cold, less than 100 K.
.
.
. 4. it is colder that the rest of the universe; that is, its effective temperature is less than 3 K.
.
. 1 points
Question 15
. What is the typical duration of a gamma-ray burst? .
. 1. less than a couple of minutes, indicating a source smaller than Mercury's orbit
.
.
. 2. several hours, indicating a source somewhat larger than the solar system
.
.
. 3. several days, indicating a size much smaller than the distance from Earth
. to .the nearest star beyond the Sun
.
.
. 4. up to about 1 hour, indicating a source less than half the size of the solar system
.
. 1 points
Question 16
. In the context of black holes, a singularity is a(n) .
. 1. place just outside the event horizon of a rotating black hole where it is
. impossible
.
to remain at rest.
.
.
.
.
. 2. place where the escape velocity exactly equals the speed of light.
.
. 3. entry point in the event horizon of a black hole through which material
. is allowed
.
to pass unhindered.
.
. 4. place where a nonzero mass occupies zero volume.
.
. 1 points
Question 17
. Sometimes particle-antiparticle pairs are created and then annihilate so quickly that
we cannot know that they ever existed. What are these particles (or antiparticles)
called? .
. 1. temporary particles
.
.
. 2. relativistic particles
.
.
. 3. virtual particles
.
.
. 4. field particles
.
. 1 points
Question 18
. How do Kerr black holes differ from Schwarzschild black holes? .
. 1. Kerr black holes rotate; Schwarzschild black holes do not.
.
.
. 2. Kerr black holes have infinite mass; Schwarzschild black holes do not.
.
.
. 3. Kerr black holes have accretion disks; Schwarzschild black holes do not.
.
.
. 4. Kerr black holes have net electric charge; Schwarzschild black holes do not.
.
. 1 points
Question 19
. The Schwarzschild radius is .
. 1. the distance to which gas is ejected in a planetary nebula.
.
.
. 2. half the diameter of the singularity in a black hole.
.
.
. 3. half the diameter of a neutron star.
.
.
. 4. the distance from the center of a black hole to the point at which the
. escape
.
velocity becomes equal to the speed of light.
. 1 points
Question 20
. What is Hawking radiation? .
. 1. stream of particles and antiparticles from just outside the event horizon
. of a. black hole
.
.
. 2. microwaves from the edge of the visible universe
.
.
. 3. electromagnetic radiation from electrons spiraling in the magnetosphere
. of a. neutron star
.
. 4. X rays from an accretion disk around a black hole
.
Question 21
. One of the first three astronomical objects detected at radio wavelengths by Grote
Reber in the late 1930s was .
. 1. the Moon.
.
.
. 2. the Sun.
.
.
. 3. the galactic center.
.
.
. 4. Jupiter.
.
. 1 points
Question 22
. BL Lacertae objects appear to be .
. 1. spiral galaxies with bright, starlike nuclei.
.
.
. 2. elliptical galaxies with bright, starlike nuclei.
.
.
. 3. active galaxies, most of whose energy is emitted by two widely spaced radio lobes.
.
.
. 4. giant irregular galaxies with neither spiral arms nor the smooth shape of elliptical galaxies.
.
. 1 points
Question 23
. The fact that quasars can be detected from distances from which even the biggest
and most luminous galaxies cannot be seen means that .
. 1. they must be far more luminous than the brightest galaxies.
.
.
. 2. they must be in directions where intergalactic absorption by dark matter is
. minimum,
.
allowing us to see them.
.
.
. 3. their spectra have not been as redshifted by their motion as those of galaxies
. and. hence they can still be seen.
.
.
. 4. they must be in directions where gravitational focusing by the masses of nearer
. galaxies
.
makes them visible from Earth.
. 1 points
Question 24
. Quasars appear to be .
. 1. very distant and intrinsically bright objects moving in random directions at high speeds.
.
.
. 2. very distant, intrinsically faint objects with very high blueshifts in their spectra.
.
.
. 3. very distant, intrinsically bright objects with very high redshifts
.
.
. 4. relatively close with very high redshifts.
.
. 1 points
Question 25
.
. Which one of the following properties do Seyfert galaxies and the Milky Way Galaxy
share? .
. 1. spectrum containing strong emission lines from elements such as highly ionized iron
.
.
. 2. significantly varying energy output over a few weeks
.
.
. 3. spiral galaxy classification
.
.
. 4. bright starlike nucleus
.
. 1 points
Question 26
. Seyfert galaxies are .
. 1. elliptical galaxies with extremely bright nuclei.
.
.
. 2. spiral galaxies with extremely active cores.
.
.
. 3. supergiant elliptical galaxies that are periodically disturbed by supernova
. explosions
.
within them.
.
.
. 4. active galaxies that shine mainly by radiation from two relatively widely
. spaced
.
radio lobes.
. 1 points
Question 27
. Quasars all appear to be .
. 1. moving across our line of sight at very high speeds, as seen in time-lapse photographs.
.
.
. 2. moving away from us at very high speeds, up to about 90% of the speed of light.
.
.
. 3. moving toward us at high speeds, as high as 90% of the speed of light.
.
.
. 4. extremely massive objects in the Milky Way Galaxy, their spectra showing very
. high
. gravitational redshift.
. 1 points
Question 28
. Seyfert galaxies are .
. 1. irregular galaxies with no shape or structure.
.
.
. 2. very small elliptical galaxies.
.
.
. 3. active galaxies with bright, starlike nuclei.
.
.
. 4. the largest galaxies in the universe.
.
. 1 points
Question 29
. The distance to the bright quasar 3C 273 is estimated to be .
. 1. just beyond the Milky Way.
.
.
. 2. 3 million ly.
.
.
. 3. 2 billion ly.
.
.
. 4. 20,000 ly.
.
. 1 points
Question 30
. What is an Einstein ring? .
. 1. arc of relativistic particles ejected from a galactic nucleus
.
.
. 2. ring of material in some spiral galaxies created by a collision with a smaller galaxy
.
.
. 3. accretion disk around a black hole
.
.
. 4. example of the image formed by a gravitational lens
.