Mastering Astronomy Exam 2
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.
Which of the following is the most basic definition of a greenhouse gas?
A gas that absorbs infrared light Greenhouse gases can therefore slow the escape of heat from a planet, because planets radiate infrared light.
Directly detecting an Earth-size planet around one of the nearest stars (besides the Sun) is roughly equivalent to trying to take a picture of a ball point from a pen at a distance of about ________ kilometers.
4000m
The Sun will exhaust its nuclear fuel in about ______
5 billion years
The Sun's average surface (photosphere) temperature is about ______.
5,800K
What is the Sun's approximate composition (by mass)?
70% hydrogen, 28% helium, 2% other elements This is also the approximate overall chemical composition of the Milky Way Galaxy.
According to modern science, what was the approximate chemical composition of the solar nebula?
98% hydrogen and helium, 2% everything else
Assuming the impact hypothesis is correct, in what way(s) was the impact important to our existence on Earth today?
It seems unlike that we would have evolved by now without the extinctions caused by the impact.
Our Sun undergoes slight orbital motion mostly due to the gravitational force exerted by Jupiter. If our solar system only contained Saturn, how would the Sun's orbital period differ?
It would be longer.
Our Sun undergoes slight orbital motion mostly due to the gravitational force exerted by Jupiter. If our solar system only contained Saturn, how would the speed of the Sun differ?
It would be slower.
What would the temperature of a planet be if its reflectivity were 1.0?
It would be very, very cold.
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. The inverse square law for light tells us that the light gets dimmer with increasing distance by the square of the distance, so tripling the distance decreases the brightness by 9x.
Earth has a relatively strong magnetic field, but Mars does not. Which of the following probably explains why Mars lacks a strong magnetic field today?
Its core is too cool for convection As discussed in the video, Mars probably had a much stronger magnetic field in its early history, but its small size has allowed it to cool much more quickly than Earth, and as a result the core became too cool for convection.
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 Size determines how long the planet can retain internal heat, which drives geological activity.
What can we infer, at least roughly, from a star's luminosity class?
Its size (radius)
According to the graph, an object 10 kilometers across hits Earth __________
once every 100 million years.
The existence of a core-mantle-crust interior structure tells us that a world __________.
once had a molten interior The interior must have once been molten so that its material could separate by density, with denser materials settling toward the core while less dense materials rose up toward the surface.
In essence, the nebular theory holds that _________.
our solar system formed from the collapse of an interstellar cloud of gas and dust
Rank the layers of the Sun's atmosphere based on their density, from highest to lowest.
photosphere, chromosphere, corona
What is a white dwarf?
The remains of a star that ran out of fuel for nuclear fusion
According to this graph, the minimum size of an object that could cause a mass extinction is a little less than _____.
10km
The first confirmed detections of extrasolar planets occurred in ____________.
1990's
Ten parsecs is about _________.
32.6 light-years You find this by remembering that 1 parsec = 3.26 light-years.
What is the probability that an object 100 meters in diameter will hit Earth during the coming year?
about 1 in 1000
How often do objects big enough to create craters like the Meteor Crater impact Earth?
about once every ten thousand years
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
Greenhouse gases
absorb infrared light and transmit infrared light.
Greenhouse gases in the atmosphere, such as carbon dioxide and water vapor, make Earth warmer than it would be otherwise because these gases __________.
absorb infrared light emitted by the surface Although the absorbed infrared light is quickly reemitted, it is reemitted in a random direction. As a result, greenhouse gases tend to slow the escape of infrared light from Earth to space, so that there is more heat (which means more energy) in the atmosphere than there would be if the infrared light escaped directly to space.
Where would you expect terrestrial planets to form in the solar nebula?
anywhere between the innermost regions (within about the inner 0.3 AU) and the frost line Terrestrial planets are made mostly of metal and rock and therefore formed in the region in which it was cool enough for metal and rock to condense but still too warm for hydrogen compounds to condense into ices. This means the region between the innermost regions (within about the inner 0.3 AU) and the frost line.
Put the following events into the correct order in which they are thought to have occurred according to the impact hypothesis.
impact, debris demolishes north america, soot released by global forest fires, long global winter, extinction of a large fraction of all species.
Where do scientists find the key evidence linking the extinction of the dinosaurs to the impact of an asteroid or comet?
in sediments separating rocks from the time when dinosaurs existed from those deposited after dinosaurs were no longer found these sediments make up what is called the K-T boundary layer, because it separates sediments containing rocks and fossils from the Cretaceous and Tertiary periods. Dinosaur fossils are found only below this layer.
On an H-R diagram, stellar radii _________.
increase diagonally from the lower left to the upper right
Which of the following is not a characteristic of the 11-year sunspot cycle?
is a characteristic: -The Sun's entire magnetic field flip-flops with each cycle, so that the overall magnetic cycle averages 22 years. -The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common. -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. is not: The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
If star A is closer to us than star B, then Star A's parallax angle is _________.
larger than that of Star B
The oxygen in Earth's atmosphere was released by
life
Where is the most CO2 that has outgassed from Earth's volcanoes?
locked up in rocks
The total amount of power (in watts, for example) that a star radiates into space is called its _________
luminosity
The axes on a Hertzsprung-Russell (H-R) diagram represent _________.
luminosity and surface temperature
All the phenomena of solar activity — including sunspots, flares, coronal mass ejections, and the sunspot cycle — are tied to changes in the Sun's __________.
magnetic field
On the H-R diagram, most stars fall into the region labeled ____________.
main sequence
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
More massive stars have __________ lives than less massive stars.
much shorter
What substances existed as solid flakes within the innermost regions (within about the inner 0.3 AUAU) of the solar system before planets began to form?
none
During a transit event, the absorption lines from the star will be
not shifted at all.
The source of energy that keeps the Sun shining today is _________.
nuclear fusion
The fundamental nuclear reaction occurring in the core of the Sun is _________.
nuclear fusion of hydrogen into helium
The overall result of the proton-proton chain is:
4 H becomes 1 He + energy
The basic fusion reaction through which the Sun produces energy is __________
4 hydrogen nuclei fuse to make 1 helium nucleus Each hydrogen nucleus is a single proton. Four of these combine to make one helium nucleus, which has two protons and two neutrons.
According to modern science, approximately how old is the Sun?
4.5 billion years
Which of the following statements are supported by the data shown?
- Which of the following statements are supported by the data shown? - Rises in global average temperature tend to be closely associated with rises in atmospheric carbon dioxide concentration. - Atmospheric carbon dioxide levels have risen dramatically over the past century.
The solar system contains vast numbers of small bodies, which we call asteroids when they are rocky and comets when they are icy. These small bodies are concentrated in the region(s) of the solar system that we call __________.
- the asteroid belt - the Kuiper belt - Oort cloud Most asteroids are found in the asteroid belt between Mars and Jupiter. Comets are concentrated in two regions: the Kuiper belt just beyond the orbit of Neptune and the much more distant and roughly spherical region known as the Oort cloud.
What two items on the list below are in balance in what we call gravitational equilibrium?
-gas pressure -gravity
According to modern scientific dating techniques, approximately how old is the solar system?
4.5 billion years
On average, how fast do the plates move on the Earth?
A few centimeters per year
Now consider the second major feature (two types of planets). Which of the following statements are true for the terrestrial and jovian planets in our solar system?
-Jovian planets are larger in size than terrestrial planets. -Jovian planets orbit farther from the Sun than terrestrial planets -Jovian planets have more moons than terrestrial planets. -Jovian planets are larger in mass than terrestrial planets In contrast, while all the jovian planets in our solar system orbit much farther from the Sun than the terrestrial planets, there are other solar systems in which jovian planets have been found to orbit much closer to their stars.
Based on the nebular theory as it explains our own solar system, which of the following should we expect to be true for other star systems?
-Many extrasolar planets should fall into the terrestrial or jovian categories. -Planetary systems should be common -Jovian planets always form farther from their star than terrestrial planets. -Planetary systems should generally have all planets orbiting in nearly the same plane.
Comets
-Meteor showers are associated with debris from comets. -Leftover planetesimals that formed in the region of the solar system now occupied by the jovian planets are called comets. -The objects that are sometimes visible in the night sky with long tails are comets -form a coma when near the Sun -visible in the sky as a fuzzy patch of light that rises and sets with the stars -most are located either in Kuiper belt or Oort cloud
All the following statements are true. Which of them are considered to be "exceptions" to the general trends described by the first three major features of the solar system?
-Our Moon has a diameter more than 1/4 the diameter of Earth. -Venus rotates in a direction opposite to the rotation of the other terrestrial planets. -Uranus rotates with an axis tilt that lies nearly in the ecliptic plane.
Which of the following statements about our solar system's terrestrial worlds are true?
-Their interiors all have a core, mantle, and crust. - All nearly the same age. -They are all made primarily of rock and metal.
Which of the following changes would cause the fusion rate in the Sun's core to increase?
-an increase in the core temperature -a decrease in the core radius
Which method(s) are based on the gravitational tug a planet exerts on its star and hence can tell us about a planet's mass?
-the astrometric method -the Doppler method
Which of the following occur as the greenhouse gas concentration increase?
-the average surface temperature rises -more infrared light is absorbed in the lower atmosphere.
What two items on the list below are in balance in what we call energy balance?
-the energy released into space -the energy produced by fusion Energy balance in the Sun refers to the balance between the energy produced by fusion in the Sun's core and the energy that the Sun releases into space.
Meteors
-visible in the sky as a bright streak of light for only a few seconds -dust particles entering Earth's atmosphere at high speed
Earth's temperature remains fairly steady, which means that Earth must return nearly the same amount of energy to space that it receives from the Sun. In what form(s) does Earth return most of this energy to space?
-visible light reflected by clouds -infrared light emitted by the surface and atmosphere -visible light reflected by the surface The total amount of energy returned to space in these three forms of radiation is nearly equal to the amount of energy that reaches Earth in the form of sunlight, which is why Earth's average temperature stays fairly steady.
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
In the context of plate tectonics, what is a subduction zone?
A place where a seafloor plate is sliding under a continental plate. This process returns seafloor crust to the mantle.
What do we mean by a "super Earth"?
A planet made of metal and rock that is larger in mass than Earth.
What do we mean by a "hot Jupiter"?
A planet that is Jupiter-like in size but orbits very close to its star
What is an extrasolar planet?
A planet that orbits a star that is not our own Sun
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.
What is a magnetosphere?
A region of space around a planet in which the planet's magnetic field can trap charged particles
What is the solar wind?
A stream of charged particles flowing outward from the surface of the Sun
Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true?
All the planets orbit counterclockwise around the Sun
As you've seen, the nebular theory predicts that a cloud that gives birth to planets should have the shape of a spinning disk. Which observable property of our solar system supports this prediction?
All the planets orbit the Sun in the same direction and in nearly the same plane
Based on current data, about what fraction of stars have one or more planets?
At least about 70%
Why is the sky blue (on Earth)?
Because molecules scatter blue light more effectively than red light.
Which of the following is not a similarity between Earth and Mars?
Both planets have similar atmospheric pressure. The surface atmospheric pressure on Mars is less than 1% that on Earth, making it so low that liquid water is not stable on the surface. Similarity -Both planets have polar caps. - Both planets have similar day lengths. - both planets have seasons, similar axis tilts.
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.
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.
Which of the following gases are greenhouse gases?
Carbon dioxide and water
Dwarf Planets
Ceres, Pluto, and Eris are all round in shape and classified as dwarf planets.
Suppose you observe two clusters of stars: Cluster A contains main-sequence stars of nearly all masses. Cluster B contains only low-mass main-sequence stars, along with many giants
Cluster A is younger than Cluster B.
The nebular theory also predicts that the cloud will flatten into a disk as it shrinks in size. Which of the following best explains why the collapsing cloud should form a disk?
Colliding cloud particles exchange angular momentum and, on average, end up with the rotation pattern for the cloud as a whole.
When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals except _________.
Compounds that ARE hydrogen compounds: water, ammonia, methane Not Carbon Dioxide
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.
As you found in Part A, early Mars had both core convection and a strong magnetosphere. What is the connection between these two things?
Core convection helps generate a magnetic field, and the magnetic field creates the magnetosphere. Early Mars had a strong magnetic field because of the combination of convection in its molten metal core and a relatively rapid rotation rate. The magnetic field created the magnetosphere that shielded the atmosphere from the solar wind.
From center to surface, which of the following correctly lists the interior layers of a terrestrial world?
Core, mantle, crust.
How does the amount of heat released in a planet's interior by radioactive decay change with time?
Drops off with time.
Each of the following statements was either true for Mars in the distant past (early Mars) or is true for Mars today. Sort the statements by dragging each into the correct bin.
Early Mars: - strong greenhouse effect -substantial volcanism and outgassing - some craters held water - strong magnetosphere - core convection Modern Mars: - surface pressure too low for stable liquid water. - Solar wind strips atmospheric gas. - very weak greenhouse effect.
What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
Gravitational force and outward pressure
Earth
Earth has a single moon that is surprisingly large compared to its planet.
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.
Why is it very hard to use the Doppler shift method of detecting planets to discover a planet like Earth?
Earth is too small in mass.
Based on this graph, which statement below most accurately describes the impacts we should expect on Earth during the coming year?
Earth will be hit by at least one object a few meters in diameter, along with many smaller objects.
Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true?
Earth would be inside the supergiant.
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.
Eris
Eris is similar in size to Pluto and also considered a dwarf planet.
Which moon is considered likely to have a deep, subsurface ocean of liquid water?
Europa
What is one reason why it is very difficult to directly take a picture of an extrasolar planet?
Extrasolar planets are very close to the star (relative to the distance to Earth).
Our Sun is a star of spectral type _________.
G
The following images represent four types (wavelength bands) of light. Rank these from left to right based on the amount of each that is emitted (as thermal radiation) by Earth's surface, from greatest to least. If you think that two (or more) types should be ranked as equal, drag one on top of the other(s) to show this equality.
Greatest: infrared Equal: visible, ultra-violet, x-ray Earth emits thermal radiation characteristic of its surface temperature, which means it is almost entirely infrared (extending, in principle, down into the radio). For Earth, the surface temperature is too low to emit any visible, ultraviolet, or X-ray light, so those are all ranked equally.
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
The solar system has two types of planets, terrestrial and jovian. According to the nebular theory, why did terrestrial planets form in the inner solar system and jovian planets in the outer solar system?
Ices condensed only in the outer solar system, where some icy planetesimals grew large enough to attract gas from the nebula, while only metal and rock condensed in the inner solar system, making terrestrial planets.
Which of the following must occur for a star's core to reach equilibrium after an initial change in fusion rate?
If the fusion rate initially increases, then the core expands. If the fusion rate initially decreases, then the core contracts.
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.
What key process underlies why Mars changed so much from its early conditions to its conditions today?
Interior cooling. Cooling of the interior explains both why core convection stopped, leading to weakening of the magnetic field and magnetosphere, and why volcanism and outgassing became so much weaker.
Why does the abundance of iridium suggest that the iridium came from an impact?
Iridium is rare on Earth's surface but common in meteorites that have impacted the Earth. iridium is relatively rare on Earth's surface but common in meteorites, and since meteorites are pieces of asteroids, we infer that the unusually high abundance of iridium in this layer came from the impact of an asteroid (or comet).
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. Heating is a consequence of conservation of energy, faster rotation is a consequence of conservation of angular momentum, and flattening is a consequence of collisions between objects in a spinning system.
This star map shows stars as we see them in our sky from Earth, centered around the constellation Canis Major. Larger dots represent brighter stars, and a few of the brightest stars are identified. From this view alone, what can you conclude about Sirius?
It has the greatest apparent brightness of any star in this region of the sky.
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. Therefore, planetesimals were built only of metal and rock within the frost line, but beyond the frost line they included ices along with metal and rock.
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. On Earth, these particles burn up in the atmosphere (creating what we see as meteors).
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.
What is the importance of the carbon dioxide (CO2) cycle?
It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.
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. Migration is necessary to explain how some very massive extrasolar planets came to be in orbits very close to their stars.
Jupiter
Jupiter has a famous storm known as the Great Red Spot.
The jovian planets in our solar system are _________.
Jupiter, Saturn, Uranus, and Neptune.
Asteroids
Leftover planetesimals that formed inside the frost line are known as asteroids. -typically orbit the Sun at approximately 3 AU -compositions similar to that of the terrestrial planets
According to our theory of solar system formation, what are asteroids and comets?
Leftover planetesimals that never accreted into planets Asteroids are the rocky leftovers of the inner solar system, and comets are the icy leftovers of the outer solar system.
The three bins represent three important properties of stars. Drag the items that we must measure in orrder to determine each property into the appropriate bin.
Luminosity: distance, apparent brightness Surface temp: color or spectral type Mass: orbital period in binary system, orbital distance in binary system.
Mars
Mars has no surface liquid water today, but shows clear evidence of such water in the distant past.
All of the following statements are true. Which one explains why Mars has lost so much more interior heat than Earth.
Mars is smaller than Earth.
Pluto
Pluto was studied up close in 2015 by the New Horizons spacecraft.
Mercury
Mercury has a greater difference in temperature between its day and night sides than any other world.
What is the main reason Mercury is much hotter than the Moon?
Mercury is closer to the Sun.
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
The terrestrial planets in our solar system are _________.
Mercury, Venus, Earth, and Mars.
Why don't we see transit events for most stars that have been found to have planets?
Most of the planets orbit the star without ever getting directly in between Earth and the star.
Neptune
Neptune has a large moon, Triton, that almost certainly once orbited the Sun independently
The impact of a 100-meter object will not cause "widespread" devastation, but it could still kill millions of people if it struck a major city. In Part C, you found that the probability of such an impact in any single year is only 1 in 1000. Suppose we learn that it has already been 1200 years since the last such impact. What would that tell us?
Nothing; we would still presume that the chance of such an impact during the next year is 1 in 1000.
From hottest to coolest, the order of the spectral types of stars is _________
OBAFGKM
Why didn't a planet form in the region of the solar system now occupied by the asteroid belt?
Orbital resonances with Jupiter disrupted orbits in this region
What do we conclude if a planet has few impact craters of any size?
Other geological processes have wiped out craters.
The Sun's visible surface (that is, the surface we can see with our eyes) is called the _________.
Photosphere
Meteorites
Pieces of asteroids that have fallen to Earth are called meteorites.
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.
Which of the following best describes the lunar maria?
Relatively smooth, flat plains on the Moon These plains are the dark, circular regions visible on the face of the Moon.
Saturn
Saturn is orbited by at least two geologically active moons: Titan and Enceladus.
Each choice that follows lists a spectral type and luminosity class for a star. Which one is a red supergiant?
Spectral type M2, luminosity class I
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
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 The magnitude scale is "backward" so that smaller numbers mean greater apparent brightness.
The gravitational force exerted on a star by a planet is
equal to that exerted on the planet by the star and in the opposite direction.
Each of the following statements applies either to the formation of terrestrial planets or of jovian planets (but not both), based on our current theory of solar system formation. Drag the statements into the appropriate bin.
Terrestrial Planets - accreted from planetesimals of rock and metal - surfaces dramatically altered during the heavy bombardment Jovian Planets - ejected icy planetesimals that are now Oort cloud comets. - large moons formed in surrounding disks of material - formed in a region of the solar system with lower orbital speeds - accreted from icy planetesimals - formed in regions cold enough for water to freeze
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.
The Sun
The Sun generates energy deep in its core through the fusion of hydrogen into helium
What would happen if the fusion rate in the core of the Sun were increased but the core could not expand?
The Sun's core would start to heat up, and the rate of fusion would increase even more.
The energy that is released in the hydrogen fusion reaction comes from __________.
The difference in mass between the four hydrogen nuclei and the single resulting helium nucleus.
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
Which of the following is not an example of tectonics
The gradual disappearance of a crater rim as a result of wind and rain.
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 At first, accretion probably arose from electrostatic attractions, but as planetesimals grew larger their gravity allowed them to accrete more efficiently (as long as they didn't suffer collisions with similar-size planetesimals).
What observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius?
The presence of many long, tall cliffs
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 Outgassing therefore released all the gases from Earth's interior that ultimately became our atmosphere or condensed to form the oceans.
Why does the Doppler method generally give a planet's "minimum mass" rather than an exact mass?
The size of the Doppler shift that we detect depends on the tilt of a planet's orbit. We get a precise mass from the Doppler method only if the planet's orbit is edge-on to us; we'll know if it is edge on because in that case we will see transits by the planet.
Which one of the following is not one of the four major features of the solar system?
The solar system contains eight planets plus dwarf planets (such as Ceres, Pluto, and Eris). The precise number of planets is not thought to be of any particular significance, and the division between "planets" and "dwarf planets" is a recent classification scheme that does not affect the basic ideas in the four major features. That is, for the purposes of the four major features, the dwarf planets are considered to be equivalent to large asteroids or comets.
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
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
What do sunspots, solar prominences, and solar flares all have in common?
They are all strongly influenced by magnetic fields on the Sun.
According to scientists, the naturally occurring greenhouse effect makes Earth about 31∘C∘C warmer than it would be if there were no greenhouse gases in our atmosphere. How do scientists "know" what Earth's temperature would be without greenhouse gases?
They calculate this temperature from Earth's reflectivity and distance from the Sun.
What is the common trait of all main-sequence stars?
They generate energy through hydrogen fusion in their core.
Why are neutrinos so difficult to detect?
They have a tendency to pass through just about any material without any interactions.
The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did the elements heavier than hydrogen and helium come from?
They were produced by stars that lived and died before our solar system was born
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
Which of the following statements is not true about the planets so far discovered around other stars?
True: -Doppler measurements indicate that most of them are much more massive than Earth. -Transit studies show that some of them orbit closer to their star than Mercury orbits the Sun. -Doppler studies show that many of them have orbits that are more eccentric than orbits of the planets in our own solar system. False: Photographs reveal that most of them have atmospheres much like that of Jupiter. With rare (and very low-resolution) exceptions, we cannot yet obtain images of extrasolar planets
Which of the following statements about the moons of the jovian planets is NOT true?
True: -One of the moons has a thick atmosphere. -Many of the moons are made largely of ices. -Some of the moons are big enough that we'd call them planets (or dwarf planets) if they orbited the Sun. False: -Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids. Most of the moons are small, and small moons generally are not spherical.
Which of the following statements comparing open and globular star clusters is not true?
True: -Stars in open clusters are relatively young, while stars in globular clusters are very old. -Open clusters are found only in the disk of the galaxy, while globular clusters may be found both in the disk and the halo of the galaxy. -For both open and globular clusters, we can assume that all the stars in a particular cluster are about the same age. False: -Open and globular clusters each typically contain a few hundred stars. many more stars than that.
Which of the following statements about our Sun is not true?
True: -The Sun contains more than 98% of all the mass in our solar system. -The Sun is made mostly of hydrogen and helium. -The Sun is a star. False: - The Sun's diameter is about 5 times that of Earth. (much larger)
Which of the following statements about Mars is not true?
True: -We have landed spacecraft on its surface. -It is considered part of our inner solar system. -It is frozen today, but it once had flowing water. False: - We could survive on Mars without spacesuits, as long as we brought oxygen in scuba tanks. you'd need protection from the cold and the ultraviolet radiation from the Sun.
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.
Uranus
Uranus has an axis tilt that gives it very extreme seasons.
Which terrestrial planet would have its surface temperature the most dramatically changed if its greenhouse gases were removed from its atmosphere?
Venus
The planet in our solar system with the highest average surface temperature is _________.
Venus - strong greenhouse effect.
Venus
Venus has a surface hot enough to melt lead as a result of an extremely strong greenhouse effect.
In Part A, you found that Earth emits only infrared light. This infrared light can be absorbed by greenhouse gases, such as carbon dioxide and water vapor, in the atmosphere. In fact, all the terrestrial planets emit infrared light from their surfaces. The following images show the four terrestrial planets in our solar system. Rank these planets from left to right based on the total amount of infrared-absorbing greenhouse gases in their atmospheres, from greatest to least.
Venus, Earth, Mars, Mercury Venus has a thick atmosphere of carbon dioxide. Earth has greenhouse gases primarily in the form of water vapor, carbon dioxide, and methane. Mars has an atmosphere made mostly of carbon dioxide, but its atmosphere is so thin that it contains less total greenhouse gas than Earth's atmosphere. Mercury has essentially no atmosphere at all.
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?
View Available Hint(s) You'll have 0.25 kilogram of the radioactive substance remaining.
The energy that warms Earth's surface comes primarily in the form of __________.
Visible light from the Sun
Which of the following is an example of convection?
Warm air expanding and rising while cooler air contracts and fall. Convection is any type of heat-driven circulation like this.
What are the appropriate units for the Sun's luminosity?
Watts
Based solely on an understanding of the greenhouse effect (as displayed in the figure), which one of the following statements is true?
We should expect an increase in the greenhouse gas concentration to lead to global warming.
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.
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.
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. The astrometric and Doppler methods give us planetary period because this period must be the same as the star's orbital period around the center of mass. The transit method gives us orbital period from the time between transits.
All of the statements that follow are true. Which one gives the 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.
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 The energy takes a long time to make its way from the core to the surface (essentially because it bounces around so much within the solar interior), but once at the surface it travels through space to Earth at the speed of light.
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 golf ball is about right for the Moon (1/4 Earth's diameter) and the baseball would work for Venus, since it is nearly the same size as Earth.
Olympus Mons is ______.
a huge volcano on Mars It is the largest mountain in the solar system.
A terrestrial world's lithosphere is ________.
a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle The depth of the lithosphere varies among the different worlds, with larger worlds (like Venus and Earth) having thinner lithospheres.
Suppose the solar nebula had been too warm for ices to condense anywhere. If a planet had still formed at Jupiter's location, it most likely would have
been similar in composition to Earth, with a much smaller mass than the real Jupiter.
On an H-R diagram, stellar masses _________.
can be determined for main-sequence stars but not for other types of stars
Which lists the major steps of solar system formation in the correct order?
collapse, condensation, accretion
As the solar nebula collapsed, it became a disk because
collisions between particles made the particles go in more-or-less the same direction.
As a general rule, smaller planets __________ than larger planets.
cool more rapidly That is why smaller worlds tend to have less geological activity -- because in a solar system that is more than 4 billion years old, these worlds have already cooled substantially.
Place the layers of the Sun into the correct order from innermost at left to outermost at right.
core, radiation zone, convection zone, photosphere, chromosphere, corona.
Rank the layers of the Sun's atmosphere based on their temperature, from highest to lowest.
corona, chromosphere, photosphere
Rank the layers of the atmosphere based on the energy of the photons that are typically emitted there, from highest to lowest.
corona, chromosphere, photosphere
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?
countless icy particles, ranging in size from dust grains to large boulders.
What is Jupiter's main ingredient?
hydrogen and helium
Which of the following types of material can condense into what we call ice at low temperatures?
hydrogen compounds
The inner planets are small and rocky and the outer planets are mostly large and gaseous because
hydrogen compounds are more abundant than rocks and metals so that beyond the frost line the gravity of large ice planetesimals could capture the abundant light gases.
The processes responsible for virtually all surface geology are _________.
impact cratering, volcanisms, tectonics, and erosion
As the solar nebula collapsed under its own gravity,
it heated up and spun up.
Mars's surface temperature would be higher if
its atmosphere contained more greenhouse gases.
Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?
plate tectonics and liquid water oceans Carbon dioxide dissolves in the oceans and becomes incorporated into carbonate rock; plate tectonics recycles the carbonate rock into the mantle, where it melts and releases its gas back to the atmosphere.
The astrometric method looks for planets with careful measurements of a star's _________.
position in the sky
Which heat source continues to contribute to Earth's internal heat?
radioactive decay
The temperature of the protoplanetary disk allowed
rocks and metals to freeze both in the inner region and outer region, and hydrogen compounds to freeze only in the outer region.
The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of __________
rocks, metals, and ices Because ices could condense only beyond the frost line, we expect jovian planets to form only beyond the frost line. Note that many extrasolar planets appear to be jovian but are located close to their stars, leading scientists to suspect that these planets migrated inward after originally forming beyond the frost lines of their star systems.
What substances were found in the innermost regions (within about the inner 0.3 AUAU) of the solar system before planets began to form?
rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form all the materials of the solar nebula were present in the inner region, but it was too hot for any of them to condense. As a result, they were all in gaseous form.
The biggest surprise from the New Horizons flyby of Pluto was learning that Pluto _________.
shows clear evidence of recent or ongoing geological activity
If Venus's atmosphere contained the same amount of greenhouse gases as Earth's atmosphere, its surface temperature would be
significantly colder
To place a star on an H-R diagram, we must know its __________.
surface temperature and luminosity
In the context of studying major bodies of our solar system, what category of object does our Moon best fit?
terrestrial world We consider the Moon to be one of the terrestrial worlds because of its similarity in size, mass, and composition to the other terrestrial worlds (Mercury, Venus, Earth, and Mars)
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)
Among main sequence stars, those with the highest surface temperatures have ___________.
the highest masses and shortest lifetimes
Observations show that interstellar clouds can have almost any shape and, if they are rotating at all, their rotation is not perceptible. However, the nebular theory predicts that a cloud will rotate rapidly once it shrinks to a relatively small size. What physical law explains why a collapsed cloud will rotate rapidly?
the law of conservation of angular momentum
The nebular theory also predicts that the cloud should heat up as it collapses. What physical law explains why it heats up?
the law of conservation of energy
Which of the following properties can be inferred from the star's orbital period?
the planet's orbital radius This is a consequence of the fact that the star and planet must have the same orbital period, and Kepler's third law tell us that the planet's orbital period depends only on its orbital radius.
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
The planets in our solar system are thought to have come from
the same cloud of gas and dust in which the Sun formed.
The proton-proton chain is _________.
the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
Which method of planetary detection works only for planets that happen to orbit their star with an orientation that causes them to pass directly in front of the star as seen from Earth?
the transit method
If the solar nebula initially had no angular momentum,
there would not be any planets orbiting the Sun
Since the Doppler shift only determines the component of the star's velocity that is moving directly away or towards us, the star is typically moving faster than the maximum speed astronomers measure. This means that the masses of the orbiting planets are typically
underestimated
To estimate the central temperature of the Sun, scientists _________.
use computer models to predict interior conditions
Suppose the solar nebula had cooled much more before the solar wind cleared away the remaining gas. In that case, the terrestrial planets likely would have ended up
with a higher abundance of hydrogen compounds and larger size.
Is it possible to determine the planet's mass from the star's velocity curve?
yes, by measuring both the star's orbital period and its change in velocity over the orbit
