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Astronomy Test Answers
Richardson
150
Astronomy
04/26/2010

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Term
Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?
Definition
Your friend will see a crescent moon.
Term
The path that led to modern science emerged from ancient civilizations in which part of the world?
Definition
the Mediterranean and the Middle East
Term
Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?
Definition
phases of Venus
Term
When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting
Definition
higher in the sky
Term
Which of the following best describes how modern astronomers view astrology?
Definition
Astrology played an important part in the development of astronomy in ancient times, but it is not a science by modern standards.
Term
The ancient Greeks get a lot of attention for their contributions to science because
Definition
they were the first people known to try to explain nature with models based on reason, mathematics, and geometry, without resort to the supernatural.
Term
The great contribution of Tycho Brahe was to
Definition
observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion.
Term
Which of the following is smallest?
Definition
size of a typical planet
Term
Based on observations of the universal expansion, the age of the universe is about
Definition
14 billion years
Term
When we see Venus in its full phase, what phase would Earth be in as seen by a hypothetical Venetian?
Definition
full
Term
In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because
Definition
our evening view of space depends on where Earth is located in its orbit around the Sun.
Term
During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
Definition
Earth is catching up with and passing by Mars in their respective orbits.
Term
Our solar system consists of
Definition
the sun and all the objects that orbits it
Term
Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter Jupiter). This photo might have been taken by
Definition
the Hubble Space Telescope (which orbits Earth)
Term
When we look at an object that is 1,000 light-years away, we see it
Definition
as it was 1,000 years ago
Term
How does Earth's varying distance from the Sun affect our seasons?
Definition
It doesn't—Earth's orbital distance plays no obvious role in the seasons.
Term
What do the structures of Stonehenge, the Templo Mayor, the Sun Dagger, and the Big Horn Medicine Wheel all have in common?
Definition
They were all used by ancient peoples for astronomical observations.
Term
He discovered that the orbits of planets are ellipses.
Definition
Kepler
Term
How long does it take Earth to complete one orbit around the Sun?
Definition
one year
Term
Which of the following statements does not use the term light-year in an appropriate way?
Definition
It will take me light-years to complete this homework assignment.
Term
What is the ecliptic plane?
Definition
The plane of Earth's orbit around the Sun
Term
Which of the following has your "cosmic address" in the correct order?
Definition
you, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
Term
For most of history, the lack of observable stellar parallax was interpreted to mean that
Definition
Earth is stationary at the center of the universe.
Term
How did the Ptolemaic model explain the apparent retrograde motion of the planets?
Definition
It held that the planets moved along small circles that moved on larger circles around Earth, and that the combined motion sometimes resulted in backward motion.
Term
What is a circumpolar star?
Definition
a star that always remains above your horizon
Term
How many galaxies are there in the observable universe?
Definition
roughly (within a factor of 10) the same as the number of stars in our galaxy
Term
Each part below describes how a few astronomical phenomena are related to time periods. Which list is correct? (Careful: some lists are partially correct.)
Definition
A)Earth's rotation defines a day.
The cycle of the Moon's phases takes about a month.
Earth's orbit defines a year.
Earth's cycle of axis precession takes 26,000 years.
Term
Only one of the statements below uses the term theory in its correct scientific sense. Which one?
Definition
Einstein's theory of relativity has been tested and verified thousands of times.
Term
What do astronomers mean by the Big Bang?
Definition
the event that marked the beginning of the expansion of the universe
Term
How many arcseconds are in 1°?
Definition
3,600
Term
Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?
Definition
Its surface is cooler than the surface of the Sun
Term
According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?
Definition
Because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system.
Term
Based on everything you have learned in this chapter, which of the following statements seems unlikely to be true?
Definition
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
Term
Which of the following statements about X rays and radio waves is not true?
Definition
X rays travel through space faster than radio waves.
Term
Which planet has a ring system?
Definition
All of the above
Term
Which of the following is not a major difference between the terrestrial and jovian planets in our solar system?
Definition
Terrestrial planets contain large quantities of ice and jovian planets do not.
Term
According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?
Definition
the law of conservation of angular momentum
Term
When a spinning ice skater pulls in his arms, he spins faster because
Definition
his angular momentum must be conserved, so reducing his radius must increase his speed of rotation.
Term
Newton showed that Kepler's laws are
Definition
natural consequences of the law of universal gravitation.
Term
Where did the elements heavier than hydrogen and helium come from?
Definition
They were produced inside stars.
Term
Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?
Definition
B)Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons.
Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons.
Term
We can see each other in the classroom right now because we
Definition
reflect visible light.
Term
We can see each other in the classroom right now because we
Definition
reflect visible light.
Term
We can see each other in the classroom right now because we
Definition
reflect visible light.
Term
Suppose you kick a soccer ball straight up to a height of 10 meters. Which of the following is true about the gravitational potential energy of the ball during its flight?
Definition
The ball's gravitational potential energy is greatest at the instant when the ball is at its highest point.
Term
we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
Definition
The planet is rotating.
Term
Which of the following represents a case in which you are not accelerating?
Definition
driving in a straight line at 60 miles per hour
Term
Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?
Definition
The cloud is cool and lies between you and a hot star.
Term
In what way is Venus most similar to Earth?
Definition
both planets are nearly the same size.
Term
Which of the following is not evidence supporting the idea that our Moon formed as a result of a giant impact?
Definition
The Pacific Ocean appears to be a large crater—probably the one made by the giant impact.
Term
Which of the following best describes the origin of ocean tides on Earth?
Definition
Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of Earth.
Term
Which of the following statements is not one of Newton's laws of motion?
Definition
What goes up must come down.
Term
The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?
Definition
30 m/s
Term
Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen?
Definition
Both will hit the ground at the same time
Term
Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?
Definition
Star X is moving away from us faster than Star Y.



Term
Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 10 years. Which of the following statements will be true after 20 years pass?
Definition
You'll have 0.25 kilogram of the radioactive substance remaining.
Term
The wavelength of a wave is
Definition
the distance between two adjacent peaks of the wave.
Term
According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them
Definition
decreases by a factor of 9.
Term
How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
Definition
The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
Term
Where are most of the known asteroids found?
Definition
between the orbits of Mars and Jupiter
Term
When a rock is held above the ground, we say it has some potential energy. When we let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground (and stays there). What has happened to the energy?
Definition
The energy goes to producing sound and to heating the ground, rock and surrounding air.
Term
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
Definition
It is closer to the stars.
Term
What do we mean when we say that the Sun is in gravitational equilibrium?
Definition
There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
Term
The Sun's average surface (photosphere) temperature is about
Definition
5,800 K
Term
The Sun's surface seethes and churns with a bubbling pattern. Why?
Definition
We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.
Term
The overall result of the proton-proton chain is:
Definition
H ⇒ 1 He + energy.
Term
Every second, the Sun converts 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons
Definition
are converted to an amount of energy equal to 4 million tons times the speed of light squared.
Term
Why do sunspots appear dark in pictures of the Sun?
Definition
They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
Term
According to modern science, approximately how old is the Sun?
Definition
4.6 billion years
Term
Why are neutrinos so difficult to detect?
Definition
They have a tendency to pass through just about any material without any interactions.
Term
To estimate the central temperature of the Sun, scientists
Definition
use computer models to predict interior conditions.
Term
What do sunspots, solar prominences, and solar flares all have in common?
Definition
The are all strongly influenced by magnetic fields on the Sun.
Term
All stars are born with the same basic composition, yet stars can look quite different from one another. Which two factors primarily determine the innate characteristics of a star?
Definition
its mass and its stage of life
Term
Which of the following statements about spectral types of stars is not generally true?
Definition
The spectral type of a star can be used to determine its distance.
Term
The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest?
Definition
The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.



Term
If Star A is close to us than Star B, then Star A's parallax angle is
Definition
larger than that of Star B
Term
How is the lifetime of a star related to its mass?
Definition
More massive stars live considerably shorter lives than less massive stars.
Term
What is the common trait of all main sequence stars?
Definition
They generate energy through hydrogen fusion in their core.
Term
What is a white dwarf?
Definition
It is the remains of a star that no longer produces energy by nuclear fusion.
Term
Consider a large molecular cloud that will give birth to a cluster of stars. Which of the following would you expect to be true?
Definition
A few massive stars will form, live, and die before the majority of the star's clusters even complete their protostar stage.
Term
We do not know for certain whether the general trends we observe in stellar birth weights also apply to brown dwarfs. But if they do, then which of the following would be true?
Definition
Brown dwarfs would outnumber all ordinary stars.
Term
What will happen to the star after stage viii?
Definition
Its outer layers will be ejected as a planetary nebula and its core will become a white dwarf.
Term
Which of the following statements about various stages of core nuclear burning (hydrogen, helium, carbon, etc.) in a high-mass star is not true?
Definition
Each successive stage lasts for approximately the same amount of time.
Term
What is a protostar?
Definition
a star that is still in the process of forming
Term
What is the CNO cycle?
Definition
The CNO cycle is a series of nuclear reactions that result overall in the fusion of four hydrogen nuclei into one helium nucleus.
Term
No stars have been found with masses greater than 100 times our Sun because
Definition
they would generate so much power that they would blow themselves apart.
Term
Which of the following statements about degeneracy pressure is not true?
Definition
Degeneracy pressure varies with the temperature of the star.
Term
What do we mean by the event horizon of a black hole?
Definition
It is the point beyond which neither light nor anything else can escape the black hole's gravity.
Term
What does cosmological redshift do to light?
Definition
stretches it in wavelength
Term
Which of the following phenomena are not thought to be results of collisions or other interactions between galaxies?
Definition
the fact that spiral galaxies have both disk and halo components
Term
Why are white-dwarf supernovae more useful for measuring cosmic distances than massive-star supernovae?
Definition
White-dwarf supernovae all have roughly the same true peak luminosity, while massive-star supernovae come in a wide range of peak luminosities.
Term
How can we see through the interstellar medium?
Definition
by observing in high-energy wavelengths such as X rays and long wavelengths of light such as radio waves
Term
Imagine that our Sun were magically and suddenly replaced by a black hole of the same mass (1 solar mass). What would happen to Earth in its orbit?
Definition
Nothing—Earth's orbit would remain the same.
Term
What do we mean by a protogalactic cloud?
Definition
It is a cloud of matter that contracts to become a galaxy.
Term
Red and orange stars are found evenly spread throughout the galactic disk, but blue stars are typically found
Definition
only near star-forming regions.
Term
Which statement about pulsars is not thought to be true?
Definition
Pulsars can form only in close binary systems.
Term
The maximum mass of a white dwarf is
Definition
about 1.4 times the mass of our Sun.
Term
Which constellation lies in the direction toward the galactic center?
Definition
Sagittarius
Term
Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?
Definition
Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted.
Term
The most basic difference between elliptical galaxies and spiral galaxies is that
Definition
elliptical galaxies lack anything resembling the disk of a spiral galaxy.
Term
What do we mean by the star-gas-star cycle?
Definition
It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium.
Term
The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with
Definition
radio telescopes observing at a wavelength of 21 centimeters.
Term
Which of the following features is not a feature of a central dominant galaxy?
Definition
They are often spiral galaxies
Term
According to present understanding, a nova is caused by
Definition
the fusion of hydrogen on the surface of a white dwarf.
Term
Current estimates place the age of the universe at about
Definition
14 billion years
Term
Where are most heavy elements made?
Definition
in stars and supernovae
Term
Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?
Definition
No, because it is not orbited by another star
Term
Most stars in the Milky Way's halo are
Definition
very old
Term
What do we call the bright, sphere-shaped region of stars that lie within a few thousand light-years of the center of the Milky Way Galaxy?
Definition
the galaxy's bulge
Term
What does Hubble's law tell us?
Definition
the more distant a galaxy,the faster it is moving away from us.
Term
What strange object do we think lies in the center of the Milky Way Galaxy?
Definition
a more than 2 milleion-solar-mass black hole
Term
What strange object do we think lies in the center of the Milky Way Galaxy?
Definition
a more than 2 milleion-solar-mass black hole
Term
What strange object do we think lies in the center of the Milky Way Galaxy?
Definition
a more than 2 milleion-solar-mass black hole
Term
The more massive a white dwarf, the
Definition
smaller its radius
Term
What do halo stars do differently from disk stars?
Definition
Halo stars orbit the galactic center with many different inclinations, while disk stars all orbit in nearly the same plane
Term
Suppose that we observe a souce of X-rays that varies substantially in brightness over a period of a few days. What can we conclude?
Definition
The X-ray souce is no more than a few light-days in diameter
Term
What is an accretion disk?
Definition
a disk of hot gas swirling rapidly around a white dwarf, a neutron star, or a black hole in a binary system.
Term
How does an accretion disk around a neutron star differ from an accretion disk around a white dwarf?
Definition
The accretion disk around a neutron star is much hotter and emits higher-energy radiation than the accretion disk around a white dwarf.
Term
In a photo like the Hubble Deep Field, we see galaxies in many different stages of their lives. In general, which glaxies are seen in the earliest (youngest) stages of their lives?
Definition
The galaxies that are farthest away
Term
Which of the following show evidence of ancient river beds?
Definition
Mars
Term
What is a primitive meteorite?
Definition
a piece of rock that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago
Term
Which direction do a comet's dust and plasma tails point?
Definition
generally away from the Sun
Term
Which statement is not true?
Definition
Objects in the Kuiper belt are made mostly of rock and metal.
Term
What is the most abundant gas in Titan's atmosphere?
Definition
nitrogen
Term
Which of the following worlds has the most substantial atmosphere?
Definition
venus
Term
Pluto is different from the other outer planets in all of the following ways except which one?
Definition
Its surface temperature is very cold.
Term
Which of the following gases is not a significant ingredient of the jovian planet atmospheres?
Definition
carbon dioxide
Term
Which of the following does not have a major effect in shaping planetary surfaces?
Definition
magnetism
Term
Why does the burning of fossil fuels increase the greenhouse effect on Earth?
Definition
Burning releases carbon dioxide into the atmosphere
Term
What mechanism is most responsible for generating the internal heat of Io that drives the volcanic activity?
Definition
tidal heating
Term
What kind of surface features may result from tectonics?
Definition
all of the above

A)valleys
B)mountains
C)volcanos
D)cliffs
Term
When we see a meteor shower, it means that
Definition
Earth is crossing the orbit of a comet.
Term
Jupiter's colors come in part from its three layers of clouds. Which of the following is not the primary constituent of one of Jupiter's cloud layers?
Definition
clouds of sulfuric acid
Term
What atmospheric constituent is responsible for the blue color of Uranus and Neptune?
Definition
methane
Term
What was the Shoemaker-Levy 9 impact?
Definition
the impact of a fragmented comet on Jupiter, carefully observed by astronomers when it occurred in 1994
Term
Which of the following best describes convection?
Definition
It is the process in which warm material expands and rises while cool material contracts and falls.
Term
Processed meteorites with high metal content probably are
Definition
chunks of a larger asteroid that was shattered by a collision.



Term
Why is Saturn almost as big as Jupiter, despite its smaller mass?
Definition
Jupiter's greater mass compresses it more, thus increasing its density.
Term
Why is Saturn almost as big as Jupiter, despite its smaller mass?
Definition
Jupiter's greater mass compresses it more, thus increasing its density
Term
What are the conditions necessary for a terrestrial planet to have a strong magnetic field?
Definition
both a molten metallic core and reasonably fast rotation
Term
Which of the following statements about the moons of the jovian planets is not true?
Definition
The majority of the moons are large enough to be spherical in shape, while only a few have the more potato-like shapes of asteroids.
Term
Why does Jupiter have three distinct layers of clouds?
Definition
The three layers represent clouds made of gases that condense at different temperatures and therefore different altitudes.
Term
Why do asteroids and comets differ in composition?
Definition
Asteroids formed inside the frost line, while comets formed outside.
Term
Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?
Definition
countless icy particles, ranging in size from dust grains to large boulders
Term
Under what circumstances can differentiation occur in a planet?
Definition
The planet must have a molten interior.
Term
The most volcanically active body in our solar system is
Definition
Io
Term
According to current ideas, Pluto is best explained as
Definition
one of the larger (if not the largest) Kuiper-belt comets.
Term
Which of the following gases absorbs ultraviolet light best?
Definition
ozone
Term
Which of the following describes erosion?
Definition
the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
Term
When you see the bright flash of a meteor, what are you actually seeing?
Definition
The glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere