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AST1002 5-13

Terms in this set (271)

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
gamma rays, X rays, ultraviolet, visible light, infrared, radio
Which forms of light are lower in energy and frequency than the light that our eyes can see?
infrared and radio
When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called _________.
photons
Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?
its wavelength and energy
Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?
Several kilometers
Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?
They have different numbers of protons in their nucleus.
Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number?
atomic number = 6; atomic mass number = 13
If we say that a material is opaque to ultraviolet light, we mean that it _________.
absorbs ultraviolet light
Suppose you look at a detailed spectrum of visible light from some object. How can you decide whether it is an emission line spectrum or an absorption line spectrum?
An emission line spectrum consists of bright lines on a dark background, while an absorption line spectrum consists of dark lines on a rainbow background.
An atom that has fewer electrons than protons is called a/an _________.
ion
Thermal radiation is defined as _________.
radiation with a spectrum whose shape depends only on the temperature of the emitting object
According to the laws of thermal radiation, hotter objects emit photons with _________.
a shorter average wavelength
Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?
the wavelengths of spectral lines in the star's spectrum
The spectra of most galaxies show redshifts. This means that their spectral lines _________.
have wavelengths that are longer than normal
What does angular resolution measure?
The angular size of the smallest features that the telescope can see.
Which of the following statements best describes the two principle advantages of telescopes over eyes?
Telescopes can collect far more light with far better angular resolution.
What is the purpose of interferometry?
It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
What do astronomers mean by light pollution?
Light pollution is light from human sources that makes it difficult to see the stars at night.
The stars in our sky twinkle in brightness and color because of _________.
turbulence in the Earth's atmosphere
What is the purpose of adaptive optics?
It reduces blurring caused by atmospheric turbulence for telescopes on the ground.
What is the purpose of interferometry?
It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?
They have a frequency of 2 hertz.
Which of the following best describes why we say that light is an electromagnetic wave?
The passage of a light wave can cause electrically charged particles to move up and down.
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?
nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons
Which of the following statements is true of green grass?
It absorbs red light and reflects green light.
Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?
The cloud is cool and lies between you and a hot star.
Which of the following statements about thermal radiation is always true?
A hot object emits more radiation per unit surface area than a cool object.
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?
Its surface is cooler than the surface of the Sun.
Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
The star is moving toward us.
Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?
Star X is moving away from us faster than Star Y.
TRUE or FALSE:
The total amount of light in the spectrum tells us the star's radius.
FALSE
We cannot measure radius from a spectrum without additional information.
The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see?
The photo will seem to show only one star rather than two.
How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.

The 8-meter telescope is 4 times larger in diameter, so its light collecting area is 42 = 16 times greater.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
It is closer to the stars.
The Chandra X-ray Observatory must operate in space because:
X rays do not penetrate Earth's atmosphere.
Which of the following is always true about images captured with X-ray telescopes?
They are always shown with colors that are not the true colors of the objects that were photographed.
Which of the following lists the planets of our solar system in the correct order from closest to farthest from the Sun?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
Which of the following statements about our Sun is not true?
Which of the following statements about our Sun is not true?
The planet in our solar system with the highest average surface temperature is _________.
Mercury
The terrestrial planets in our solar system are _________.
Mercury, Venus, Earth, and Mars.
The jovian planets in our solar system are _________.
Jupiter, Saturn, Uranus, and Neptune.
When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals except _________.
carbon dioxide
In essence, the nebular theory holds that _________.
our solar system formed from the collapse of an interstellar cloud of gas and dust
According to modern science, what was the approximate chemical composition of the solar nebula?
98% hydrogen and helium, 2% everything else
The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did these elements come from?
They were produced by stars that lived and died before our solar system was born.
According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?
It got hotter, its rate of rotation increased, and it flattened into a disk.
Which of the following types of material can condense into what we call ice at low temperatures?
Hydrogen compounds
According to our present theory of solar system formation, which of the following lists the major ingredients of the solar nebula in order from the most abundant to the least abundant?
hydrogen and helium gas; hydrogen compounds; rock; metal
What do we mean by the frost line when we discuss the formation of planets in the solar nebula?
It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.
What do we mean by accretion in the context of planet formation?
The growth of planetesimals from smaller solid particles that collided and stuck together
According to our theory of solar system formation, what are asteroids and comets?
Leftover planetesimals that never accreted into planets
What do we mean by the period of heavy bombardment in the context of the history of our solar system?
The first few hundred million years after the planets formed, which is when most impact craters were formed
What is the giant impact hypothesis for the origin of the Moon?
The Moon formed from material blasted out of the Earth's mantle and crust by the impact of a Mars-size object.
According to modern scientific dating techniques, approximately how old is the solar system?
4.5 billion years
Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is _________.
much larger

The planets are much more widely separated in the outer solar system than in the inner solar system.
How is Einstein's famous equation, E=mc2, important in understanding the Sun?
the Sun generates energy to shine by losing 4 million tons of mass each second
In what way is Venus most similar to Earth?
Both planets are nearly the same size
Which planet listed below has the most extreme seasons?
Uranus
Which of the following is not a major pattern of motion in the solar system?
Nearly all comets orbit the Sun in same direction and roughly the same plane.

This statement is untrue because comets of the Oort cloud, which are the most numerous of all comets, have randomly oriented orbits going in all directions around the Sun.
The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?
The diameter of Earth's Moon is about 1/4 that of Earth.
According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?
The law of conservation of angular momentum
According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?
The law of conservation of energy
According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?
It flattened as a natural consequence of collisions between particles in the nebula.
What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?
The temperatures at which various materials will condense from gaseous form to solid form.
According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not true?
The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?
The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.
According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?
As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks.
Why are terrestrial planets denser than jovian planets?
The terrestrial planets formed in the inner solar nebula, where only dense materials could condense.
About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the very first generation of star systems in the universe probably consisted only of hydrogen and helium. Which of the following statements is most likely to have been true about these first-generation star systems?
There were no comets or asteroids in these first-generation star systems.
Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock?
3.75 billion years

The current 10 micrograms of potassium-40 is 1/8 of the original 80 grams, which means the amount of potassium-40 has declined by a factor of 8. Therefore, three half-lives have passed (since 23 = 8) and the rock is 3×1.25 = 3.75 billion years old.
How do scientists determine the age of the solar system?
Radiometric dating of meteorites
Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of _________.

a golf ball to a baseball
a dust speck to a golf ball
a dust speck to a basketball
a golf ball to a beach ball
a golf ball to a baseball
What do we mean when we say that the terrestrial worlds underwent differentiation?
When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.
A terrestrial world's lithosphere is ________.
a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle
The two most important processes in heating the interiors of the terrestrial worlds are:
(1) Heat deposited by the process of formation; (2) heat released by radioactive decay.
What is a magnetosphere?
a region of space around a planet in which the planet's magnetic field can trap charged particles
The processes responsible for virtually all surface geology are _________.
impact cratering, volcanisms, tectonics, and erosion
In the context of planetary geology, what do we mean by outgassing?
the release by volcanism of gases that had been trapped in a planetary interior
Which of the following is not an example of tectonics?
The gradual disappearance of a crater rim as a result of wind and rain.
Suppose we represent Earth with a basketball. On this scale, most of the air in Earth's atmosphere would fit in a layer that is _________.
about the thickness of a sheet of paper
Why is the sky blue (on Earth)?
Because molecules scatter blue light more effectively than red light
Which of the following is the most basic definition of a greenhouse gas?
a gas that absorbs infrared light
Which of the following best describes the lunar maria?
relatively smooth, flat plains on the Moon
Why does the Moon have a layer of "powdery soil" on its surface?
It is the result of countless tiny impacts by small particles striking the Moon.
What observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius?
the presence of many long, tall cliffs
Olympus Mons is ______.
a huge volcano on Mars
Which of the following is not a similarity between Earth and Mars?
Both planets have similar atmospheric pressure.
Primary reason why the surface of Venus today is some 450°C hotter than the surface of Earth?
Venus has a much stronger greenhouse effect than Earth.
What do we mean by a runaway greenhouse effect?
a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere
On average, how fast do the plates move on the Earth?
a few centimeters per year
In the context of plate tectonics, what is a subduction zone?
A place where a seafloor plate is sliding under a continental plate.
What is the importance of the carbon dioxide (CO2) cycle?
It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.
Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by _____.
human activities that increase the concentration of greenhouse gases in Earth's atmosphere
Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny?
its size
The cores of the terrestrial worlds are made mostly of metal because ______.
metals sunk to the centers a long time ago when the interiors were molten throughout
The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that _________.
a large baked potato takes longer to cool than a small baked potato
Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
not much - on human time scales, the mantle looks like solid rock
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?
Mars's interior has cooled so much its molten core layer no longer undergoes convection.
What are the two geological features that appear to set Earth apart from other terrestrial worlds in our solar system?
plate tectonics and a high level of erosion
Which of the following general statements about Earth's atmosphere is not true?

Gas high in the atmosphere absorbs dangerous X rays from the Sun.
The oxygen in our atmosphere was released by living organisms.
Without the relatively rare gas called ozone, Earth's surface would be bathed in dangerous ultraviolet light from the Sun.
The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.
The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.

Only greenhouse gases influence surface temperature, and neither oxygen nor nitrogen is a greenhouse gas.
Which of the following best describes how the greenhouse effect works?
A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.
Suppose that Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be ________.
well below the freezing point of water
Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
The maria formed after the heavy bombardment ended.
Which of the following best describes the geological histories of the Moon and Mercury?
Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
The atmosphere is too cold and thin for liquid water today, yet we see evidence that water flowed on the surface in the past.
What statement about Mars might have led to a significant loss of atmospheric gas to space?
Mars lost any global magnetic field that it may once have had.
Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle
What statement about Venus offers evidence of a global repaving about a billion years ago?
Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.
Which of the following best explain what we think happened to outgassed water vapor on Venus?
Ultraviolet light split the water molecules, and the hydrogen then escaped to space.
Why are there fewer large impact craters on the Earth's seafloor than on the continents?
The crust on seafloors is younger than on continents, so it has had less time in which to suffer impacts.
Which two factors are most important to the existence of plate tectonics on Earth?
mantle convection and a thin lithosphere
Why does Earth have so little carbon dioxide in its atmosphere compared to Venus?
Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere.
Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?
plate tectonics and liquid water oceans
Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?
Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the greenhouse effect.
Which of the following correctly lists two key pieces of evidence that, together, indicate that we should expect human activity to cause global warming?

(1) The burning of fossil fuels is a form of human activity; (2) Human activity is always bad for the environment.
(1) The carbon dioxide cycle regulates Earth's climate; (2) Human activity has disrupted the carbon dioxide cycle.
(1) Carbon dioxide tends to make planets warmer than they would be otherwise; (2) Measurements demonstrate that human activity is raising the carbon dioxide concentration in the atmosphere.
(1) We can learn about past climate from ice cores; (2) Ice cores show that Earth naturally has cooler and warmer periods.
(1) Carbon dioxide tends to make planets warmer than they would be otherwise; (2) Measurements demonstrate that human activity is raising the carbon dioxide concentration in the atmosphere.
The choices below describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)


Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.

Largest size means the highest interior temperature.
The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)

Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.

The smallest size means the least geological activity to have erased past impact craters, so lots of craters would still be present.
The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.

This planet is large enough to have had outgassing make an atmosphere, and rotates fast enough to drive winds.
What would happen to Jupiter if we could somehow double its mass?
Its density would increase but its diameter would barely change.
According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?
Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.
Why does Jupiter have three distinct layers of clouds?
The three layers represent clouds made of gases that condense at different temperatures.
Explain why we see horizontal "stripes" in photographs of Jupiter and Saturn
The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.
Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains why?
Temperatures on Jupiter and Saturn are too high for methane to condense.
Why is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?
Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.
What fact is most important in explaining the tremendous tidal heating that occurs on Io?
Io orbits Jupiter on an elliptical orbit, due to orbital resonances with other satellites.
Which of the following is most unlikely to be found on Titan?
lakes of liquid water in the warmer equatorial regions
Why do astronomers believe that Triton is a captured moon?
Triton orbits Neptune in a direction opposite that of Neptune's rotation.
According to current understanding, which of the following is required in order for a planet to have rings?
The planet must have many small moons that orbit relatively close to the planet in its equatorial plane.
Which of the following gases is not a significant ingredient of the jovian planet atmospheres?

water
hydrogen
helium
carbon dioxide
carbon dioxide
Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?
They actually contain relatively little material in a gaseous state.
Which of the following is not a piece of evidence supporting the idea that Europa may have a subsurface ocean?

Photos of Europa's surface show regions that appear to consist of jumbled icebergs frozen in place.
Europa has a magnetic field that appears to respond to Jupiter's magnetic field.
Astronomers have detected small lakes of liquid water on Europa's surface.
Europa's surface shows very few impact craters.
Astronomers have detected small lakes of liquid water on Europa's surface.
Which statement about Saturn's rings is not true?

The rings must look much the same today as they did shortly after Saturn formed.
Some features of the rings are shaped by small moons that actually orbit within the ring system.
The rings are so thin that they essentially disappear from view when seen edge-on.
The large gap known as the Cassini Division is shaped by an orbital resonance with the moon Mimas, which orbits well outside the rings.
The rings must look much the same today as they did shortly after Saturn formed.
Which statement about asteroids is not true?

Many but not all orbit the Sun in the asteroid belt.
Most asteroids are not spherical in shape.
Some are more like loosely bound piles of rubble than solid chunks of rock.
If we could put all the asteroids together, they would make an object about the size of Earth.
If we could put all the asteroids together, they would make an object about the size of Earth.
Which statement is not thought to be true of all comets in our solar system?

All comets orbit the Sun.
All comets are icy in composition.
Comets always have tails.
All comets are leftover planetesimals that originally condensed beyond the frost line in the solar nebula.
Comets always have tails.
Which of the following statements is not true?

Objects in the asteroid belt and Kuiper belt orbit the Sun in nearly the same plane as the planets, but objects in the Oort cloud do not.
Objects in the Oort cloud contain large proportions of ice.
Objects in the Kuiper belt are made mostly of rock and metal.
Objects in the asteroid belt are made mostly of rock and metal.
Objects in the Kuiper belt are made mostly of rock and metal.
The asteroid belt is located _________.
between the orbits of Mars and Jupiter
A rock found on Earth that crashed down from space is called _________.
a meteorite
A typical meteor is created by a particle about the size of a _________.
pea
What do we mean by a primitive meteorite?
a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago
Which direction do a comet's dust and plasma tails point?
generally away from the Sun
When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called _________.
the coma
The total number of comets orbiting the Sun is estimated to be about _________.
1 trillion
According to current evidence, Pluto is best explained as ______.
a large member of the Kuiper belt
What is Eris?
An icy object that orbits in the Kuiper belt and is more massive than Pluto
What is Charon?
the largest of Pluto's three known moons
What do we mean by a mass extinction?
the extinction of a large fraction of the world's plant and animal species in a relatively short period of time
If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because ______.
of global climate effects initiated by dust and smoke that entered the atmosphere after the impact
Objects the size of the one that exploded over Chelyabinsk (Russia), causing significant damage, probably hit Earth at least __________.
once a century
In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?

the Oort cloud
the atmosphere of Jupiter
the rings of Saturn
the asteroid belt
the rings of Saturn
Which of the following is not a piece of evidence supporting the idea that Pluto is a large comet of the Kuiper belt?

Pluto is not the largest object orbiting in the region of the Kuiper belt.
Triton, which must once have orbited the Sun before being captured by Neptune, is significantly larger than Pluto.
Pluto's orbit is very similar to the orbits of other known Kuiper belt comets.
Pluto grows a coma and a long tail when it is at the point in its orbit closest to the Sun.
Pluto's composition appears to match that of other known Kuiper belt comets.
Pluto grows a coma and a long tail when it is at the point in its orbit closest to the Sun.
Which of the following is not a piece of evidence supporting the idea that an impact caused the mass extinction that occurred 65 million years ago?

Grains of quartz formed under high pressure are found in a layer of clay that dates to 65 million years ago.
A large impact crater along the coast of Mexico dates to 65 million years ago.
Unusually large abundances of iridium and other rare metals are found in a layer of clay that dates to 65 million years ago.
Fossilized dinosaur bones contain fragments of rock from the impact.
Fossilized dinosaur bones contain fragments of rock from the impact.
Suppose that large jovian planets had never formed in our solar system. Which of the following would most likely be true?

There would be a large empty region in our solar system between the orbit of Mars and the Kuiper belt.
Earth would have suffered far fewer impacts.
Neither the asteroid belt nor Oort cloud would exist.
Earth would orbit much closer to the Sun.
Neither the asteroid belt nor Oort cloud would exist.
Which of the following statements best describes the size of the largest asteroid, Ceres?
It is a little less than half the diameter of our Moon.
If we could put all the asteroids together, their total mass would be _________.
much less than the mass of any terrestrial planet
Why didn't a planet form where the asteroid belt is now located?
Gravitational tugs from Jupiter prevented material from collecting together to form a planet.
Gaps in the asteroid belt (often called Kirkwood gaps) are caused by ______.
orbital resonances with Jupiter
When you see the bright flash of a meteor, what are you actually seeing?
the glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere
Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?
Your meteorite is a fragment from the core of a large asteroid that shattered in a collision.
Suppose there were no solar wind. How would the appearance of a comet in our inner solar system be different?
It would have only one tail instead of two.
Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude?
It has been on its current orbit for only a very short time compared to the age of our solar system.
When we see a meteor shower, it means that _________.
Earth is crossing the orbit of a comet
Why won't Pluto collide with Neptune?
Pluto orbits the Sun exactly two times for every three Neptune orbits, which ensures they never come close together.
What is Pluto's moon Charon thought to have in common with our own Moon?
It probably formed as a result of a giant impact.
What best describes why scientists seek to identify even very small asteroids that could potentially hit Earth?
To try to prevent an impact that might destroy a town or city.
Which of the following statements is not true about the planets so far discovered around other stars?

Transit studies show that some of them orbit closer to their star than Mercury orbits the Sun.
Doppler measurements indicate that most of them are much more massive than Earth.
Doppler studies show that many of them have orbits that are more eccentric than orbits of the planets in our own solar system.
Photographs reveal that most of them have atmospheres much like that of Jupiter.
Photographs reveal that most of them have atmospheres much like that of Jupiter.
What is an extrasolar planet?
A planet that orbits a star that is not our own Sun
The first confirmed detections of extrasolar planets occurred in ____________.
the 1990's
What do the astrometric, Doppler, and transit methods share in common?
They all search for planets by measuring properties of a star rather than of the planets themselves.
The astrometric method looks for planets with careful measurements of a star's _________.
position in the sky
In essence, the Kepler mission searched for extrasolar planets by ____________.
monitoring stars for slight dimming that might occur as unseen planets pass in front of them
Can we determine orbital distances for extrasolar planets using the astrometric, Doppler, or transit methods?
Yes: All three methods give us direct information about a planet's orbital period, from which we can use Newton's version of Kepler's third law to calculate the planet's distance.
Why do we say that the Doppler method gives a planet's "minimum mass"?
The size of the Doppler shift that we detect depends on the tilt of a planet's orbit.
What do we mean by a "hot Jupiter"?
a planet that is Jupiter-like in size but orbits very close to its star
Overall, what do current data suggest about planetary types in other planetary systems?
Planets come in a wider range of types than the planets in our solar system.
Based on current data, about what fraction of stars have one or more planets?
at least about 70%
Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?
Jovian planets can migrate from the orbits in which they are born.
Which of the following might explain the lack of "water worlds" —small planets made mostly of water or other hydrogen compounds—in our own solar system?
In our solar system, the solar wind did not clear out gas until relatively late.
How is the GAIA mission relevant to the search for extrasolar planets?
It can detect planets through the astrometric method.
In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?

a low-mass planet that is far from its star
a low-mass planet that is close to its star
a massive planet that is far from its star
a massive planet that is close to its star
a massive planet that is close to its star
Suppose a planet is discovered by the Doppler method and is then discovered to have transits. In that case, we can determine all the following about the planet except ______________.

its rotation period
its physical size (radius)
its orbital period
its density
its precise mass
its rotation period
Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?

Other planetary systems will have far more numerous asteroids and comets than actual planets.
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
Planets are common, and many or most stars have them.
Within a star's planetary system, all its planets will tend to orbit in the same direction and approximately the same plane.
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun?
It causes the Sun to move in a small ellipse with an orbital period of about 12 years.
Suppose you are using the Doppler method to look for planets around another star. What must you do?
Compare many spectra of the star taken over a period of many months or years.
The transit method allows us in principle to find planets around __________.
only a small fraction of stars that have planets
You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?
The planet must be closer to the star than Earth is to the Sun.
Which of the following will allow you to learn something about a transiting planet's atmospheric composition?
Compare spectra obtained before and during an eclipse.
Very few of the known extrasolar planets have sizes as small as Earth. The most likely reason for this fact is that ________.
small planets are more difficult to detect than larger planets
To date, we've found very few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?
We have not yet been searching for planets at such distances for a long enough time.
Current evidence suggests that some massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?
These planets migrated inward after being born on orbits much farther from their stars.
Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn't our own solar system end up with any hot Jupiters?
Our solar nebula must have been blown into space shortly after the formation of the jovian planets.
When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars?
In a decade or two, through space observatories now in the early planning stages.
Which of the following is not a characteristic of the 11-year sunspot cycle?

The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.
The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
The Sun's entire magnetic field flip-flops with each cycle, so that the overall magnetic cycle averages 22 years.
The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous.
The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.

The sunspot cycle is not steady at all. Even the "11 years" is only an average, as cycle length varies between about 7 and 15 years. The number of sunspots at solar maximum also varies significantly, and it appears there have been times (such as the Maunder minimum) when the sunspot cycle virtually ceased to operate.
According to modern science, approximately how old is the Sun?
4 1/2 billion years
The Sun will exhaust its nuclear fuel in about ______.
5 billion years
Which of the following correctly describes how the process of gravitational contraction can make a star hot?
When a star contracts in size, gravitational potential energy is converted to thermal energy.
The source of energy that keeps the Sun shining today is _________.
nuclear fusion
What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
gravitational force and outward pressure
Energy balance in the Sun refers to a balance between _________.
the rate at which fusion generates energy in the Sun's core and the rate at which the Sun's surface radiates energy into space
When we say that the Sun is a ball of plasma, we mean that _________.
the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)
What is the Sun made of (by mass)?
70% hydrogen, 28% helium, 2% other elements
From center outward, which of the following lists the "layers" of the Sun in the correct order?
Core, radiation zone, convection zone, photosphere, chromosphere, corona
What are the appropriate units for the Sun's luminosity?
watts
The Sun's surface, as we see it with our eyes, is called the _________.
photosphere
The Sun's average surface (photosphere) temperature is about ______.
5,800 K
What is the solar wind?
a stream of charged particles flowing outward from the surface of the Sun
The fundamental nuclear reaction occurring in the core of the Sun is _________.
nuclear fusion of hydrogen into helium
The proton-proton chain is _________.
the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
The overall result of the proton-proton chain is:
4 H becomes 1 He + energy
To estimate the central temperature of the Sun, scientists _________.
use computer models to predict interior conditions
Why are neutrinos so difficult to detect?
They have a tendency to pass through just about any material without any interactions.
The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about _________.
a few hundred thousand years ago
What happens to energy in the Sun's convection zone?
Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.
What do sunspots, solar prominences, and solar flares all have in common?
They are all strongly influenced by magnetic fields on the Sun.
How is the sunspot cycle directly relevant to us here on Earth?
Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
Which of the following choices is not a way by which we can study the inside of the Sun?

We can send a space probe into the Sun's photosphere.
We can probe the interior of the Sun by studying the vibrations in its photosphere.
We can study solar neutrinos.
We can make a computer model of the Sun's interior that allow us to predict the observable properties of the Sun.
We can send a space probe into the Sun's photosphere.
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?
It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
When is/was gravitational contraction an important energy generation mechanism for the Sun?
It was important when the Sun was forming from a shrinking interstellar cloud of gas.
What do we mean when we say that the Sun is in gravitational equilibrium?
There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
Which of the following is the best answer to the question, "Why does the Sun shine?"
As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
How does the Sun's mass compare to Earth's mass?
The Sun's mass is about 300,000 times the mass of the Earth.
Which of the following best describes why the Sun emits most of its energy in the form of visible light?
Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.
The Sun's surface seethes and churns with a bubbling pattern. Why?
We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.
Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?
The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is _________.
converted to an amount of energy equal to 4 million tons times the speed of light squared
Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
If the Sun's core suddenly shrank a little bit, what would happen in the Sun?
The core would heat up, fusion rates would increase, the core would re-expand.
Why does the Sun emit neutrinos?
Fusion in the Sun's core creates neutrinos.
If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?
Fusion reactions in the Sun have ceased within the past few minutes.
Why do sunspots appear dark in pictures of the Sun?
They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
How can we best observe the Sun's chromosphere and corona?
The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.
The intricate patterns visible in an X-ray image of the Sun generally show _________.
extremely hot plasma flowing along magnetic field lines
How can we measure the strength of magnetic fields on the Sun?
By looking for the splitting of spectral lines in the Sun's spectrum
Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because _________.
Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits
Which of the following choices is not a way by which we can study the inside of the Sun?
We can send a space probe into the Sun's photosphere.
A computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield for your new computer. (It's even "on sale" !) Why do you turn down this excellent offer?
Neutrinos rarely, if ever, interact with your computer.
Astronomers can measure a star's mass in only certain cases. Which one of the following cases might allow astronomers to measure a star's mass?

The star is a member of a binary star system.
The star is of spectral type A.
We know the star's luminosity and distance.
The star is of spectral type G.
The star is a member of a binary star system.
Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?

Spectral type G2, luminosity class V
Spectral type M2, luminosity class I
Spectral type M1, luminosity class V
Spectral type O9, luminosity class I
Spectral type M2, luminosity class I
What is the approximate chemical composition (by mass) with which all stars are born?
three quarters hydrogen, one quarter helium, no more than about 2% heavier elements
The total amount of power (in watts, for example) that a star radiates into space is called its _________.
luminosity
According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us triples?
Its apparent brightness will decrease by a factor of 9.
Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?
Calculate the star's luminosity if we know its distance, or calculate its distance if we know its luminosity.
If star A is closer to us than star B, then Star A's parallax angle is _________.
larger than that of Star B
Ten parsecs is about _________.
32.6 light-years
Star A has an apparent magnitude of 3 and star B has an apparent magnitude of 5. Which star is brighter in our sky?
Star A
From hottest to coolest, the order of the spectral types of stars is _________.
OBAFGKM
Our Sun is a star of spectral type _________.
G
Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?
spectroscopic binary
The axes on a Hertzsprung-Russell (H-R) diagram represent _________.
luminosity and surface temperature
What can we infer, at least roughly, from a star's luminosity class?
its size (radius)
On an H-R diagram, stellar masses _________.
can be determined for main sequence stars but not for other types of stars
How is the lifetime of a star related to its mass?
More massive stars live much shorter lives than less massive stars.
What is the common trait of all main sequence stars?
They generate energy through hydrogen fusion in their core.
Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true?
Earth would be inside the supergiant.
What is a white dwarf?
the remains of a star that ran out of fuel for nuclear fusion
Which of the following statements comparing open and globular star clusters is not true?
Open and globular clusters each typically contain a few hundred stars.
What do we mean by the main-sequence turnoff point of a star cluster, and what does it tell us?
It is the spectral type of the hottest main sequence star in a star cluster, and it tells us the cluster's age.
Which of the following statements about spectral types of stars is not generally true?

The spectral type of a star can be determined by identifying lines in its spectrum.
The spectral type of a star can be used to determine its distance.
The spectral type of a star can be used to determine its color.
The spectral type of a star can be used to determine its surface temperature.
The spectral type of a star can be used to determine its distance
You observe a star and you want to plot it on an H-R diagram. You will need to measure all of the following, except the star's _________.

mass
apparent brightness
distance
spectral type
mass
The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest?

The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.
The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.
The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs.
The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.
The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.
The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is most likely to be located in the halo of our galaxy?

The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.
The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.
The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.
The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs.
The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.

This is an old cluster so it must be a globular cluster, and most globular clusters are in the halo of the galaxy.
All stars are born with the same basic composition, yet stars can differ greatly in appearance. Which two basic factors are most important in determining the current appearance of a star?
its mass and its stage of life
Based on the definition of apparent brightness, which units are appropriate for its measurement?
watts per square meter
Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore:
Both stars have the same luminosity, but the apparent brightness of Star B is four times that of Star A.
A star with a parallax angle of 1/20 arcsecond is _________.
20 parsecs away
A star's color is related to it's surface temperature because _________.
stars emit thermal radiation
Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude?
Rigel has a higher surface temperature than Sirius.
To calculate the masses of stars in a binary system, we must measure their _________.
orbital period and average orbital distance
Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes significantly dimmer for about 2 hours. The most likely explanation is that _________.
the star is a member of an eclipsing binary star system
The approximate main-sequence lifetime of a star of spectral type O is _________.
3 million years
How did astronomers discover the relationship between spectral type and mass for main sequence stars?
By measuring the masses and spectral types of main-sequence stars in binary systems.
Sets with similar terms