ASTRON 83695

subject Type Homework Help
subject Pages 24
subject Words 3056
subject Authors Eric Chaisson, Steve McMillan

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page-pf1
Hydrogen lines are weak in M class stars because they have much less of it than do A
class stars.
The spectral lines of each element are distinctive to that element, whether we are
looking at emission or absorption lines.
If a star has a parallax of 0.25", then its distance is about 13 light-years.
Cometary dust tails lag behind the bluish ion tails as the comet rounds the Sun.
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Herschel's original disk model placed us close to the center of the Galaxy.
Compared to an open cluster, a globular cluster will have more hot, blue stars.
All the terrestrial planets lie inside the asteroid belt.
Stars evolve along the main sequence.
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The surface of Mars is surprisingly smooth and featureless.
Neap tides occur at first and third quarter phases of the Moon.
Radio waves, visible light, and X-rays are all types of electromagnetic radiation.
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While there are none yet, in the very distant future, most normal matter will be in the
form of black dwarfs.
A white dwarf's atoms have their electron orbitals crushed as closely as the Exclusion
Principle allows.
We would expect other planets beyond our own solar system to orbit the equators of
their home stars, as our own planets orbit the Sun.
Quasars were used to determine the size of the Local Supercluster.
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The cosmic microwave background is the total of all the radio emissions from all the
galaxies and quasars in the universe.
To get the space velocity of a star in three dimensions, you need its proper motion,
distance, and radial velocity.
The "pulse" from a pulsar is due to the rapidly expanding and contracting outer shell of
the star.
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Most pulsars are known only as radio sources, but a few of the younger ones, like the
Crab and Vela, also give off visible and even X-ray energy.
The cosmological redshift is a direct measure of the expansion of the universe, thus
independent of direction.
No communication is possible across an event horizon.
There is less ammonia in the atmospheres of Uranus and Neptune than in Jupiter or
Saturn.
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The supermassive black holes that may be powering active galaxies emit only
synchrotron radiation.
The latest observations of distant Type I supernovae suggest the universe is slowing
down more than we had expected.
Radio galaxies emit only radio waves, and are not otherwise observable.
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Most of the mass in the universe is dark matter.
Granulation is the most obvious proof of solar convective energy transport.
Collisions between galaxies have little effect on the individual stars.
Most of our detailed knowledge of the jovian planets comes from the Hubble Space
Telescope.
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While our Magellanic Clouds are irregulars, the companions to Andromeda are
ellipticals.
Most naked-eye stars would fall to the top left on the H-R diagram.
Both Pluto and Charon are tidally locked to always keep the same faces toward each
other, rotating and revolving around their common center of mass every 14.2 hours.
As yet, no human probe has left our solar system and approached another star.
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Saturn's rings are extremely old, possibly older than four billion years.
Compared to when it was on the surface, a satellite in an orbit whose radius is about 4
times the Earth's radius will experience about 1/16 the force due to the Earth's gravity.
In the Big Bang model, two possible fates exist: expansion forever, or cosmic collapse.
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You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It
would be classified a
A) Sc.
B) Sb.
C) Sa.
D) SO.
E) E7.
If the density of the universe is greater than critical, then
A) there is more matter than energy.
B) the universe is closed, gravity wins, and will shrink to the Big Crunch.
C) the universe is flat, and Euclid is right.
D) the universe will continue expanding forever.
E) the universe will end up as nothing but black holes.
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What is true of the Moon's orbital and rotational periods?
A) The rotational period is longer.
B) The orbital period is longer.
C) The rotational period varies with the Moon's phase.
D) They are equal.
E) The orbital period is greatest at full moon.
The fact that the Earth has moved along its orbit in the time it took to rotate once is the
reason for
A) the difference between solar and sidereal time.
B) precession.
C) seasons.
D) the position of the Celestial Equator.
E) Earth's 23.5-degree tilt.
A maximum in solar activity should next occur about
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A) 2015.
B) 2017.
C) 2019.
D) 2023.
E) 2027.
Which of these is the next evolutionary track for the Large Magellanic Cloud?
A) contraction into a spiral
B) expansion into a giant elliptical
C) It will become a satellite galaxy of Andromeda.
D) It will be free of our Local Group.
E) collision with the Milky Way
Which of these are not associated with the active Sun?
A) sunspots
B) prominences
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C) granulation
D) flares
E) aurora
In a very young star cluster, while the most massive stars are swelling up into giants,
the least massive stars are
A) also evolving off the main sequence as well.
B) continuing to shine as stable main-sequence stars.
C) blowing off shells as planetary nebula instead.
D) collapsing directly to white dwarfs.
E) still on the zero-age main sequence.
According to Copernicus, retrograde motion for Venus must occur around
A) inferior conjunction, when it passes between us and the Sun.
B) quadrature, when the planet is 90 degrees away from the Sun.
C) greatest elongation, when the planet is farthest from the Sun.
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D) superior conjunction, when the planet is on the far side of the Sun.
E) opposition, when the planet lies opposite the Sun in the sky.
Green light has a shorter wavelength than orange light. In a 5 inch telescope, green light
will
A) provide better angular resolution than orange light.
B) come to the same exact focus as orange light.
C) provide worse angular resolution than orange light.
D) allow dimmer stars to be observed.
E) reduce the effects of atmospheric turbulence.
As a spaceship nears an event horizon, a clock on the spaceship will be observed
A) to run faster.
B) to stop.
C) to run slowly.
D) to run backwards.
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E) to run the same as one on Earth.
What statistic below has changed the most in the last decade?
A) the masses of the Galilean moons
B) the compositions of moons of Uranus
C) the rotational period of the Jovian moons
D) the densities of the larger moons
E) the number of known Jovian moons
The tidal streams mapped in the Halo are similar to ________ in our solar system.
A) the asteroid belt between Mars and Jupiter
B) meteor swarms in old comet orbits
C) the rings around the jovians
D) the moons orbiting planets
E) the solar wind
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Meteor showers are
A) usually annual events, as the orbits again intersect.
B) caused by the Earth passing near the orbit of an Earthgrazing asteroid.
C) caused by the Earth passing near the orbit of an old short-period comet.
D) Both A and B are correct.
E) Both A and C are correct.
Two stars both have parallaxes of 0.023", but star A has apparent magnitude +2.3, while
star B is magnitude +7.3. Which statement is true?
A) Star A must be ten times closer.
B) Star B must be ten times more luminous.
C) Nothing, since we do not know their absolute magnitudes.
D) Star A is both 100 brighter and more luminous than star B.
E) Star A is both 100 brighter and larger than star B.
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If the Sun were replaced by a one-solar-mass black hole,
A) all terrestrial planets would fall in immediately.
B) we would still orbit it in a period of one year.
C) we would immediately escape into deep space, driven out by its radiation.
D) our clocks would all stop.
E) life here would be unchanged.
What explanation does general relativity provide for gravity?
A) Gravity is the result of curved spacetime.
B) Gravity is directly proportional to the mass of the attracting body.
C) Gravity is inversely proportional to the radius of the body.
D) Gravity is the opposite of the electromagnetic force.
E) Gravity can affect only massive particles, not massless photons.
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The larger terrestrial planets have surface features that tend to be
A) older.
B) younger.
C) more cratered.
D) more icy.
E) more rocky.
A proposed explanation for gamma-ray bursters is
A) hypernova-making black holes and bipolar jets.
B) coalescence of a neutron star binary.
C) collisions between two white dwarfs.
D) Both A and B are possible.
E) All three are possible.
When mass is accreted into a black hole, what fraction of the total mass-energy can be
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radiated away?
A) 0.007%
B) 0.08%
C) 1.4%
D) 20%
E) 50%
The surface of Venus can be observed with
A) the Mt. Wilson 100" telescope.
B) radar observations.
C) most amateur telescopes.
D) the Hubble Space Telescope.
E) All of these have provided detailed observations about the surface of our sister
planet.
Why are the rings of Saturn so bright?
page-pf15
A) They are made of frozen metallic hydrogen.
B) They are made of glassy beads expelled by the volcanoes of Enceladus.
C) They are made of metallic iron, never rusted by exposure to oxygen.
D) Light reflected off of gigantic Titan reinforces the sunlight.
E) They are made of young, fresh water ice.
In general, the brightest star in a given constellation is designated as alpha.
What made supernova 1987A so useful to study?
A) We saw direct evidence of nickel to iron decay in its light curve.
B) Its progenitor had been observed previously.
C) In the Large Magellanic Cloud, we already knew its distance.
D) It occurred after new telescopes, such as Hubble, could observe it very closely.
E) All of the above are correct.
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Which statement about the Magellanic Clouds is false?
A) They are both irregular galaxies.
B) They are companions of the Milky Way.
C) They contain regions of rapid star formation.
D) They are the two closest galaxies to us.
E) They are close to the south pole of the sky.
Which of these observations of Galileo refuted Ptolemy's epicycles?
A) the complete cycle of Venus' phases
B) the rotation of sunspots across the Sun's surface
C) the revolution of Jupiter's moons around it
D) the craters on the Moon
E) the visibility of many more stars with the telescope
page-pf17
Which of these radio waves would fall in the "water hole"?
A) 15,000 cm in wavelength.
B) 6.563 10-5 cm in wavelength.
C) 19 cm wavelength
D) 150 cm in wavelength.
E) 243 cm in wavelength
What two things are needed to create an emission nebula?
A) interstellar gas and dust
B) hydrogen fusion and helium ionization
C) cool stars and much interstellar dust
D) hot stars and interstellar gas, particularly hydrogen
E) hydrogen gas and carbon dust
Visible sunspots lie in the
page-pf18
A) chromosphere.
B) transition zone.
C) corona.
D) radiative zone.
E) granulation in the photosphere.
The H-R diagram can plot
A) temperature versus mass.
B) radius versus luminosity.
C) temperature versus luminosity.
D) apparent magnitude versus spectral classes.
E) radius versus mass.
The absolute magnitude of the Sun is ________.
page-pf19
A wave with a period of .01 seconds has a frequency of ________ Hz.
How has the chemical composition of the Sun changed in the last 4.5 billion years?
How will this affect its future?
The critical density must include both matter and ________.
page-pf1a
Why can the Hubble Space Telescope give us better direct measurements of star
diameters than larger Earth-based telescopes can?
Edwin Hubble first found the distance to M31 in Andromeda with its ________ variable
stars in its spiral arms.
The major product of the fusion of 4 protons in the Sun's core is a ________ nucleus.
page-pf1b
Contrast the Great Red and Great Dark Spots.
Outside our Earth, the most likely places for life are the planet ________ and jovian
moon ________.
What are the measured densities of the exoplanets called "hot Jupiters," and why are
these densities inconsistent with theoretical models?
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Knowing a cluster's turn-off mass tells you the cluster's ________.
At the top of the distance ladder sits ________.
Briefly describe how Hubble classified the galaxies visually.
In brightness, Jupiter is second only to the planet ________ most of the time.
page-pf1d
Why is hydrogen less obvious in B stars than in A class?
Discuss the nature of the Miller-Urey experiments. What are the results of these
experiments?
What are redshift surveys designed to show?
page-pf1e
Why did the quasar epoch end?

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