Astronomy 1010 Midterm 2 HW
When viewed through a telescope, Uranus and Neptune are distinctly bluish green in color. What gas is responsible for this striking appearance?
methane
After it was discovered, astronomers predicted Uranus's orbit using Newton's laws of motion and gravity, which had worked extremely well for all of the other planets. To their surprise, they found that their observations of Uranus's motion through the sky did not match their predictions. Which of the following would be the most logical next step?
Check for other previously undiscovered factors that might alter Uranus's orbit while still allowing it to obey Newton's laws of motion and gravity.
Why is Jupiter reddish in color?
because of the composition of its atmosphere
What is the name of the brown disk rotating around the protostar in the following image?
protoplanetary disk
Earth's interior is heated by
radioactive decay and tidal effects.
The following graph shows multiple transit events recorded while observing a star. The colored arrows indicate transits caused by three different planets. Rank the orbital periods of these planets, from shortest to longest. Order of Planetary formation
shortest to longest 1. red planet 2. blue planet 3. purple planet
Based on the information above, which of the following properties of a planet is most important in determining its level of recent geological activity?
size
The probability of an asteroid or large meteoroid impacting Earth in the next century is low but not zero. The meteorite that created Meteor Crater in Arizona had a mass of about 10^7 kg and impacted at 12 km/s; it left a crater 1 km in diameter. Using the equation for kinetic energy, EK=12mv2, arrange these hypothetical meteoroids, with their corresponding masses and velocities, in order of their destructive capacity, if they were to impact Earth.
smallest to largest 1. 10 million kg/ 12 km/s 2. 1 million kg/ 50 km/s 3. 45 million kh/ 8km/s 4. 10 million kg/ 30 km/s
Deep in the interiors of the giant planets, water is still a liquid even though the temperatures are tens of thousands of degrees above the boiling point of water. This can happen because
the pressure inside the giant planet is so high
If a moon revolves opposite to a planet's rotation, it probably
was captured after the planet formed.
Impacts on the terrestrial worlds
are less common than they used to be.
Stellar occultations are the most accurate way to measure the _________ of a Solar System object.
diameter
The words weather and climate
- refer to very different size scales - refer to very different time scales
Comparing objects in a related group can reveal patterns among them. These patterns in turn can help us learn more about those objects than we could by studying each individually. Select all of the following choices that describe the patterns that you've observed. As you do so, think about the implications of how the Solar System may have formed.
-All planets orbit the sun in the same direction -The closest planets to the Sun are much smaller than the planets that are farther away. -The orbits of the outer planets (those most distant from the Sun) are spaced farther apart from one another than the orbits of the inner planets. -All planets orbit the Sun in a roughly flat plane.
The greenhouse effect plays a major role in the climate of a planet. Visit the Greenhouse Effect AstroTour, and use what you learn there to choose all the statements below that are correct. Note that 273 K = 0°C = 32°F.
-If there were no greenhouse effect, liquid water would not exist on the surface of the Earth. -The more carbon dioxide there is in an atmosphere, the stronger the greenhouse effect will be. -The Earth has reached thermal equilibrium, emitting the same amount of energy into space as it absorbs from the Sun
Compare the atmospheric properties of the planets in the table to the right. The surface temperature is the average for the entire planet in units of Kelvin (subtract 273 from that number to convert it into units of Celsius). The surface pressure is related to how thick the atmosphere is (thicker atmospheres have more air molecules packed into the same volume, and thus higher pressure). Given the information in this table, how would you explain the difference in greenhouse effect strength for each of the planets?
-Mars has a weak greenhouse effect because it has very low surface pressure. -Venus has a very strong greenhouse effect because it has a high percentage of carbon dioxide in its atmosphere and also a high surface pressure.
Comparing objects in our Solar System can give us important clues toward understanding their properties that we wouldn't obtain through just studying each object independently. Comparing Earth's Moon to those of the other planets may also help us understand more about it. Examine this table and choose the statements below it that match your observations.
-Only half of the inner planets have moons. -The Earth's moon is unique in that it is much larger than the moons of the other inner planets.
Once all the giant planets were discovered, scientists could compare their properties to learn something about them. Study this picture, and choose the following options that match your observations.
-Some planets differ considerably in color from one another. -The planets range from having very distinct feature details with a variety of colors to being completely featureless and monochrome.
Considering what you know of the formation of objects in the inner versus outer Solar System, and given the information in the figure, which of these statements are factors in the Moon's lack of geological activity compared to Io?
-The Moon is made of material that has a higher melting point. -Jupiter is much more massive than the Earth.
What is an accretion disk, and what are its characteristics? Select the true statements regarding accretion disks.
-The shape and motion of the accretion disk are the reason that the subsequently formed planets all orbit in or near the equatorial plane of the star. -An accretion disk's radius is typically hundreds of AU. -Conservation of angular momentum leads a cloud to form a disk rather than collapse entirely
The upper graph shows the carbon dioxide content in Earth's atmosphere as a function of time, and the lower graph shows the average yearly temperature in Antarctica, where the carbon dioxide levels were measured. Note that the units of time are in thousands of years. Study the above figure, then select all the statements below that are correct.
-There are cyclical temperature variations seen on this graph (a periodic increase, then decrease) every few 10,000 to 100,000 years or so. -The temperature is directly related to the amount of carbon dioxide in the atmosphere—an increase in one coincides with an increase in the other.
Jupiter and Saturn, despite being considerably farther from us than the inner terrestrial planets, are very bright in our sky. Which of the following choices are possible explanations for this?
-They are larger than the terrestrial planets. -They are more reflective (higher albedo) than most of the terrestrial planets.
Which of the following are characteristics of regular moons?
-They have orbits that lie nearly in the equatorial planes of their planets. -They revolve around their planets in the same direction as the planets rotate. -They are usually tidally locked to their parent planets.
What causes the auroras of the giant planets?
-charged particles -strong magnetic fields
Geologists can find the actual age of features on a world by
-radioactive dating of rocks retrieved from the world. -comparing cratering counts on one world to those on another.
How would you explain the difference in cratering between these two pictures?
The surface on the right has experienced more recent volcanism or erosion than the surface to the left.
Put the following stages of planet formation in order of occurrence.
1. An interstellar cloud collapses into a disk of gas and dusk. 2. Gas pushes smaller dust grains into larger dust grains. 3. Larger dust grains grow into clumps. 4. Clumps of dust collide and stick, forming planetesimals. 5. KM-sized planetesimals attract other objects by gravity. 6. Planets of Various Sizes form.
Rank the following events in the order that corresponds to the formation of a planetary system
1. Gravity collapses a cloud of interstellar gas. 2. A rotating disk forms and dust grains stick together by static and electricity. 3. Small bodies collide to make smaller bodies. 4. Primary atmospheres form. 5. A stellar wind "turns on" and sweeps away gas and dust, removing a primary atmospheres from planets. 6. Secondary atmospheres form.
Place in chronological order the following steps in the formation and evolution of Earth's atmosphere:
1. hydrogen and helium are captured from the protoplanetary disk 2. hydrogen and helium are lost from the atmosphere 3. volcanoes, comets, and asteroids increase the inventory of volatile matter 4. life releases co2 from the subsurface into the atmosphere 5. plant life converts co2 to oxygen 6. oxygen enables the growth of new life forms
The total mass of Earth 's atmosphere is 5.27×10^18 kg and nitrogen makes up about 75.5 percent of its atmospheric mass. What is the mass of nitrogen in Earth's atmosphere?
75.5/100 x 5.27x 10^18 answer- 3.98 x 10^18 kg
A bar is a measure of atmospheric pressure, where one bar is equivalent to Earth's atmospheric pressure at sea level. Venus's atmosphere has a pressure of 92 bars. Water pressure in Earth's oceans increases by one bar for every 10 m of depth. How deep would you have to go to experience pressure equal to the atmospheric surface pressure on Venus?
920 m deep why? Since one bar is equivalent to 10 meters of depth in water, you need to multiply the number of bars of Venus's atmosphere by 10 meters per bar. The atmospheric pressure is 92 bars. 92 bars × 10 m/bar = 920 meters
A new star is forming inside this glowing cloud of gas. The dark band in the middle is made of a disk of thick dust, which obscures the light within it and hides the forming star from view. Newly forming stars are surrounded by gas and dust. Based on this observation--and your previous observations about the relative orbits, positions, and sizes of the planets--what is the most likely scenario for the formation of the Solar System?
A cloud of gas and dust collapsed into a flattened disk, within which the Sun and planets formed.
The level of each of the surface-shaping processes that occur on a planet throughout its history will determine how its surface appears. The terrestrial planets were formed in basically the same environment, so we can assume that the average frequency of impacts for all of the terrestrial planets has been about the same. In a hypothetical scenario where impacts are the only process that ever shape planetary surfaces, how would the surfaces of the terrestrial planets compare?
All of the planets would have roughly the same number of craters per area.
Why would bringing a sample back to Earth for analysis yield a more accurate age estimate for more recent volcanic activity?
Astronomers could use radiometric dating on the rocks
What was the evidence that indicated volcanic activity ended a billion years ago?
Astronomers counted the number of craters for a given region on the surface.
Based on the relation shown here between rising carbon dioxide (CO2) concentrations and average global temperatures, what is a logical prediction about what would happen if CO2 levels were to continue to rise?
Average global temperatures would increase.
When a protostellar cloud spins faster as it collapses, it also heats up. As the protostellar gas heats up, individual particles move faster and the gas expands, potentially stopping the collapse of the cloud before it can form a star system. Whether the cloud collapses or not depends on its moment of inertia, that is, the way the mass is distributed with respect to its axis of rotation. The following figure shows how the moment of inertia varies for three different shapes.
Big round ball of gas, flatter smaller ball of gas, flat ball of gas w/ red dot
The oxygen molecules in Earth's atmosphere
are the result of life
Consider the case of a single particle within the rings that has a highly elliptical and/or highly inclined orbit, such that its orbital shape is different from the other particles in the ring. What will likely happen to that particle?
Collisions with other particles and the gravitational force of the rings will gradually nudge it into a more circular orbit within the flat plane of the rings.
On which of the following does plate tectonics occur?
Earth
Study the sizes of the gas giants shown in the image above (the distance from the Sun increases from left to right), and choose the best explanation that accounts for their differences in size.
Gas giants decrease in size with increased distance from the Sun because the Solar Nebula was less dense farther out.
The Voyager spacecraft made close-up observations of Saturn's rings that seemed to have no explanation. In particular, Saturn's F Ring appeared twisted, which apparently did not follow Newton's law of gravity and the expected orderly orbits of particles through collisions and gravitational interactions. Given this observation, what is the most logical step in the scientific process?
In keeping with the laws of physics, further observations must be made to search for previously undiscovered objects that might gravitationally influence the rings.
A clue to the process of planetary formation comes from meteorites, which are pieces of debris that have fallen from space to Earth. Most meteorites are made of materials that have remained unchanged since the time that the Solar System was first forming, which make them excellent indicators of what conditions were like during that time.
Individual particles in the nebula stick together to form larger pieces which later collide with and stick to other pieces to gradually form larger objects, which eventually grow to the size of a planet.
Of the four large Galilean moons orbiting Jupiter, Io is the closest to the planet. Considering Io's size and location in the Solar System, what is the most likely reason for Io's high level of geological activity?
Io's proximity to Jupiter provides a current source of internal heat.
Uranus is visible to the naked eye, a bit brighter than the faintest naked-eye stars. However, it was not until well after the invention of the telescope in the late 18th century that Uranus was accidently discovered. How could people have missed this naked-eye planet until then? Compare Uranus's properties in the following chart to the other planets, then select the option that could explain why Uranus was harder to discover.
It has a longer orbital period than Jupiter and Saturn
Why has the Great Red Spot been seen for only 400 years?
It was 400 years ago that Jupiter was first examined through a telescope.
Gaseous
Jupiter, Saturn, Uranus Neptune
Choose the statement that corresponds to the biggest factor that resulted in Mars having a thinner atmosphere than Earth and Venus.
Mars is less massive than Earth and Venus.
Rocky
Mercury, venus, earth, mars, ceres
What is the most likely reason for the different levels of geological activity between the Galilean moons?
Moons farther away from Jupiter experience weaker tidal heating.
Uranus's orbit did not appear to behave according to Newton's laws of motion and gravity. The most likely culprit for Uranus's misbehaving orbit was the gravitational influence of another planet. Using Newton's laws, astronomers were able to calculate exactly where they would expect this still-undiscovered planet to be. When telescopes were pointed at this position, Neptune was seen. What does this imply?
Newton's laws have been verified by yet another test, so we should use them with high confidence until and unless they are falsified by future tests.
Rank these hypothetical moons from oldest to youngest based on their cratering. You can assume the moons have never been volcanically active.
Oldest-youngest 1. a moon completely covered in craters, old and new 2. a moon partially covered in craters 3. a moon with very few craters
If all the inner planets formed from the same processes, why would Earth and Mars be the only ones with moons? One possibility is that it was difficult for the inner rocky planets to acquire moons, and Earth and Mars obtained theirs only through some lucky event. We can compare the three moons to each other and to other objects in the inner Solar System to get an idea of what might have happened. Shown below are images of the moons, with information about their sizes and densities. Also shown are the sizes and densities of some other relatively small objects in the inner Solar System.
Phobos and Deimos have properties that suggest that they are the same type of object as c-type asteroids.
Rock/Ice
Pluto, Eris
Astronomers have determined that the gas giants are made mostly of hydrogen and helium. Given what you have learned about planetesimal formation through accretion, and the types of materials that condensed at certain distances from the Sun, which of the following is the most likely way that the gas giants formed?
Rock, metal, and ices made of materials such as water, ammonia, and methane, condensed into a solid and grew large enough to gravitationally attract hydrogen and helium gas from the Solar Nebula.
The colored bands of Jupiter and Saturn are due in part to their compositions: Water and ammonia clouds reflect white light, and ammonium hydrosulfide clouds reflect brown and red light. Alternating cells of rising and falling air can bring ammonia to higher altitudes, where it can condense into visible clouds, or they can push the air down into lower altitudes, making the deeper ammonium hydrosulfide cloud layer visible. The bands of Jupiter are more obvious than those of Saturn, with brighter and more highly varying colors. Compare the cloud layers of Jupiter and Saturn shown to determine why.
Saturn's different cloud layers are deeper, making them harder to see.
It is unlikely that the Moon formed elsewhere and was captured by Earth's gravity, since it may be impossible for the Earth to capture an object as large as the Moon. It is also of note that the Moon contains an unusually low quantity of volatiles, which are materials like water that are easily vaporized at high enough temperatures. Based on this, and given the moon's density, which of the following formation scenarios of the Moon most closely matches our observations?
The Moon accreted from the debris of the impact of a large object with the surface of the Earth.
Why do Jupiter and Saturn appear red/white and brownish orange, while Uranus and Neptune are blue? From the following figures displaying the composition of the Jovian planets with depth, choose the most likely reason for this difference. Note that we are looking at/through the upper cloud layers of each planet, which gives us the perception of a visible surface. Labels of "ice" in the figure refer to clouds made of tiny ice crystals, not a solid layer of ice.
The cloud tops of Jupiter and Saturn have a different composition from the cloud tops of Uranus and Neptune.
Based on the law of conservation of angular momentum, what would happen to a collapsing cloud of gas and dust--isolated in space with no external forces--as its size decreases?
The cloud will spin faster
The following graph shows the concentrations of carbon dioxide (CO2) and methane (CH4) in Earth's atmosphere for the past few hundred thousand years along with global temperatures. How do the current levels of carbon dioxide and methane in the atmosphere compare with the values seen over the last 800,000 years?
The current concentrations of both are far higher than the rest of the graph.
Observations show that, in general, larger planets and moons have had geological activity more recently than smaller bodies have. All of the planets show past signs of volcanism, tectonics, and/or erosion, but only the larger ones are still geologically active today. Why is this? One reason has to do with the planet's interior. Most of the heat inside of Earth is left over from the accretion process during Earth's formation. What would you expect to have happened as the Earth (or any other planet) cooled after its formation?
The hard crust thickened, closing off volcanic vents, and the mantle began to solidify, slowing the motion that causes volcanism and tectonics.
If Saturn's rings are made of individual small particles at varying distances from the planet, and given what you know of the laws of physics as governed by gravity, how would you expect these particles to behave?
The particles closer to Saturn will orbit faster around the planet than those farther away.
The following graph shows the relative concentrations of carbon dioxide (CO2) and methane (CH4) in Earth's atmosphere for the past few hundred thousand years. What, if any, correlation is there between the concentrations of carbon dioxide and methane?
Their concentrations appear to rise and fall together.
Why do Jupiter and Saturn have no blue methane cloud tops?
They are too warm for methane to condense.
How do astronomers measure the size of the Great Red Spot?
They compare its dimensions to the known diameter of Jupiter.
Which of the giant planets has the most extreme seasons?
Uranus
Which of the following worlds does not show evidence of the current presence of liquid or frozen water?
Venus
Venus is hot and Mars is cold primarily because
Venus has a much thicker atmosphere
Venus and Earth are similar in size, so they should have had similar amounts of volcanic outgassing adding to the atmosphere, and similar gravities resulting in a similar loss of atmospheric gas to space. Why, then, are their atmospheres so different? This table shows the composition of the planets' atmospheres if all the carbon dioxide that exists anywhere on the planet were included. Carbon dioxide is added to the atmosphere through volcanic outgassing, and it is removed as it is absorbed by liquid water and then chemically combined with rock. Based on the text above and what you see in the table, what is the most likely reason Venus has a stronger greenhouse effect than Earth?
Venus is closer to the Sun, so any liquid water that might have existed on the surface in the distant past would have evaporated away faster than on the Earth.
The four planets closest to the Sun have similar compositions (rock/metal), and all have solid surfaces. They are therefore grouped together as terrestrial ("Earth-like") planets. Even though they formed from the same process of accretion in the Solar Nebula, you'll see here that their surfaces are significantly different from one another
Volcanism- rising mantle material erosion- wind, ice impacts- meteorites
The following graph shows the concentrations of carbon dioxide (CO2) and methane (CH4) in Earth's atmosphere for the past few hundred thousand years along with global temperatures. What is the correlation between concentrations of these two chemicals and global temperature?
When concentrations are high global temperatures are high.
According to the data, the global average temperature of the Earth is increasing. Based on the two plots below, what is likely causing this?
a sudden increase in the strength of the greenhouse effect over the past 100-200 years
The search for extrasolar planets has uncovered a phenomenon astronomers call a "hot Jupiter." If our Solar System had one, where would it orbit, relative to the other planets?
closest to farthest from sun 1. Hot jupiter 2. mercury 3. venus 4. earth 5. mars 6. jupiter
The composition of the protoplanetary disk varies with distance from the protostar due to temperature. Starting with those closest to the protostar, place these materials in order based on where they can be found predominantly in their solid states
closest to furtherest 1. Iron, silicates, carbon 2. Water 3. methane, ammonia, CO
The similarity of Mars' tiny moons to asteroids suggests that they wandered away from the nearby asteroid belt and were captured by Mars' gravity. It is difficult to explain, however, how a relatively small planet like the Earth would be capable of capturing an object as large as the Moon. If it wasn't captured, then it must have either formed simultaneously with the Earth or separated from the Earth due to some event that happened later. We can get an idea of which scenarios are reasonable by looking at the composition of the two, which we can gather from their densities. Examine the figure to the right, which shows the approximate density of the Earth's layers in g/cm3. If the density of the Moon is 3.34 g/cm3, which layer of the Earth is it most similar to?
crust
Place in order of diameter the following types of extrasolar planets.
largest to smallest -puffy jupiter -super-jupiters -mini neptunes -super earths
The AstroTour illustrates what the surface temperatures of Venus, Earth, and Mars would be without atmospheres, and it also shows the current value for each planet, with their actual atmospheres. Place the planets in order based on the discrepancy between their surface temperatures with and without their atmospheres.
least difference- most 1. mars 2. earth 3. venus
The periodic rise and fall of Earth's average temperature over 10,000s to 100,000s of years is due to the Milankovitch cycle, which is caused by periodic variations in the Earth's axis tilt and the eccentricity of its orbit. Ice ages occur when the axis tilt is low, and periods of relative warmth occur when it is high. As the amount of liquid water on Earth changes due to evaporation, precipitation, and freezing, the level of carbon dioxide removed from the air also changes, such that the greenhouse effect is strengthened during periods of intense cold and weakened during periods of intense warmth. This helps the Earth regulate its temperature and move out of periods of extreme climate without becoming like Mars or Venus. Based on the trends seen in this graph, what would you expect Earth's temperature to do over the next few thousand years?
decrease toward the next ice age
Individual cloud layers in the giant planets have different compositions. This happens because
different volatiles freeze out at different temperatures.
Which is not a reason for the large size of volcanoes on Mars compared to Earth's smaller volcanoes?
distance from the sun
The following graph shows the relative concentrations of carbon dioxide (CO2) and methane (CH4) in Earth's atmosphere for the past few hundred thousand years. Approximately how often is there an especially high peak in concentrations of both chemicals?
every 100,000 years
the seasonal variations of the terrestrial planets.
greatest-smallest 1. mars 2. earth 3. venus 4. mercury
Different materials condense into clouds at different temperatures, as shown in these plots of the temperatures of the cloud layers of Jupiter and Uranus.
highest lowest temp 1. water ice 2. ammonium hydrosulfide ice 3. ammonia ice 4. hydrogen sulfide ice 5. methane ice
If a quantity is conserved, it means that it
it does not change
If we experience a year that is much hotter than the previous year, this means that Earth is going through a global warming trend, where the temperature will now continually increase each year.
it is impossible to tell with one year of data
Why did scientists suspect that the Moon cooled quickly?
its small
Place these volatiles in order of the temperatures at which each will condense to form a cloud layer on one of the four Jovian planets.
lowest temp to highest temp 1. methane ice 2. ammonia ice 3. ammonium hyrdosulfide ice 4. water ice 5. ammonia droplets
The distinct layers of Earth's atmosphere vary in temperature in a somewhat surprising way. Arrange these four layers in ascending order, based on the temperature at the upper boundary of each.
lowest- highest temp 1. mesosphere 2. troposphere 3. stratosphere 4. thermosphere
Whether a planet has an atmosphere or not depends on a number of factors: mass, temperature, composition of the crust, volcanic activity, and complex evolutionary processes. Rank the planets according to how well they retain their atmospheres, using the following criteria: • The planet that still maintains its primary atmosphere, ranks first. • The planet that lost its primary atmosphere but retains a dense secondary atmosphere, ranks second. • The planet that lost its primary atmosphere and retains a tenuous secondary atmosphere, ranks third. • The planet that retained neither its primary nor secondary atmospheres, ranks last.
most successful- least 1. jupiter 2. venus 3. mars 4. mercury
A planet's temperature depends on its distance from the Sun as well as the strength of its greenhouse effect. Let's remove the effect of distance from the Sun by just considering how the temperature of a planet changes due to the presence of its atmosphere. From the numbers given in the animation, calculate the difference in temperature for each planet with and without its atmosphere, and then rank the planets in order of increasing greenhouse effect.
smallest- largest 1. mars 2. earth 3. venus
Imagine that a star-forming cloud collapses but retains all of its mass in a single blob. In order to conserve angular momentum, the cloud must
spin faster
Scientists determine the geological history of the moons of the outer planets from
surface features.
Correctly position these four planets within the accretion disk of our early Solar System based on the materials that were present where they formed.
temp the highest to temp the lowest- Earth- Jupiter-Saturn -Uranus
Methane gas absorbs red light, and methane clouds reflect blue light, giving Uranus and Neptune their distinctive blue colors. Why do Uranus and Neptune have methane clouds, but Jupiter and Saturn do not? Study the red curves in the following figures to determine which factor most likely plays a role in the composition of each planet's cloud tops.
temperature
How has the global climate been changing over the past 100+ years?
the climate is getting warmer with time
Zonal winds on the giant planets are stronger than those on the terrestrial planets because
the giant planets rotate faster.
Auroras are the result of
the interaction of particles from the Sun and Earth's atmosphere and magnetic field
The terrestrial planets and the giant planets have different compositions because
the terrestrial planets are closer to the Sun
angular momentum is only approximately conserved. This is because
there are small external forces acting—friction and air resistance, for example.
The diagram shown indicates the location of exoplanets orbiting their star. The light green ring represents the habitable zone for that star. Determine whether each of the planets in this system is located in a region that is too hot, too cold, or just right for liquid water to potentially exist on the surface.
too hot for liquid water- b, c, d, e just right- f
