Astronomy HW 8
Select all the terrestrial planets that have atmospheres.
Mars Earth Venus
The image shows a representation of a planetary disk surrounding a star. Identify the materials that will condense at the indicated location in the figure.
Metals only
The image shows a representation of a planetary disk surrounding a star. Identify the materials that will condense at the indicated location in the figure.
Metals, rock, and water
Which of the following features of the Solar System are explained by the solar nebula theory?
Most planets rotate about their axes in the same direction. All estimates of the age of the Solar System are approximately the same. The composition of the outer planets is similar to the Sun's.
For many years, Pluto was called a planet. What did astronomers discover that led to revising its status?
Objects as large as Pluto had been discovered farther out.
What characteristics made Pluto difficult to categorize as a normal terrestrial or gas giant planet? (Select all that apply.)
Pluto is made of ice as well as rock. Pluto's orbit is tilted by a significant angle relative to the ecliptic plane. Pluto is much smaller.
Identify the indicated objects in this image.
Protostars Disks of gas and dust
Arrange the sentences to describe how astronomers use a spectrum from a planet.
1. An astronomer observes a planet with a telescope. 2. The light collected is passed through a spectrometer, dispersing the spectrum. 3. The astronomer measures the wavelengths. 4. Absorption features are compared to lab results to determine what chemicals are present in the planet's atmosphere.
Arrange these substances in order of increasing density. (Put the least dense at the top.)
1. Helium gas 2. Water ice 3. Silicate rock 4. Iron and nickel
Use the table to help you rank the elements from most common (top) to least common (bottom) in the Solar System.
1. Hydrogen 2. Helium 3. Oxygen 4. Carbon 5. Iron
Rank the terrestrial planets by the mass of their atmospheres, putting the one with the most atmosphere at the top.
1. Venus 2. Earth 3. Mars 4. Mercury
According to the ages of rocks from Earth, the Moon, and meteorites, the Solar System formed approximately ____ years ago.
4.6 billion
Which is the best scientific estimate for the age of the Solar System?
4.6 billion years
The Sun contains more than ____ the mass of all the other bodies in the Solar System combined. Choose the largest answer that is true.
700 times
How much of the mass of the Solar System is in the planets, asteroids, and comets?
A very small fraction of it
The image shows the result of what method of exoplanet detection?
Direct imaging
Which among the following are terrestrial planets? (Select all that apply.)
Earth Mars Venus
Select all of the following that are evidence of collisions late in the planet-forming process.
Earth's moon Craters on the Moon and Mercury Venus's and Uranus's retrograde rotations
Select the reasons it is easier to take a picture of a young exoplanet using infrared wavelengths than visible light.
Forming exoplanets are hot and generate their own light. Stars are dimmer in infrared than visible wavelengths.
Select all the chemicals likely to be found in interstellar grains in the solar nebula.
Frozen water Silicates Carbon compounds Iron compounds
Which features are typical of Jovian planets in our solar system? (Select all that apply.)
Gaseous composition Thick atmosphere Large mass and radius
Why is iron concentrated in the cores of planets?
Iron was able to sink to the core when forming planets melted in impacts.
Identify the Jovian planets in the following list. (Select all that apply.)
Jupiter Uranus Neptune
Which of the following are inner planets in our Solar System?
Mars Earth
What were the impacts of leftover planetesimals on larger planetary bodies? (Select all that apply.)
Mercury may have lost much of its crust in a collision with a large planetesimal. Mercury, the Moon, and other terrestrial planets and satellites were battered by collisions. Venus's and Uranus's unusual spin axes may have resulted from collisions with planetesimals.
Identify the composition of planets that form at the indicated locations.
Metals and rock: A Metals, rock, and water: B Metals, rock, water, and other gases: C
Identify the composition of a planet that will form at the indicated location in the figure.
Metals and silicates
Is the Sun the only star with planets?
No, we have found hundreds of planets around other stars.
Most comets orbit far from the Sun in the _______ cloud.
Oort.
Select all the choices that can be true of asteroids.
Small rocky bodies Orbit the Sun between Jupiter and Mars Small metallic bodies
Which features are typical of terrestrial planets in our solar system? (Select all that apply.)
Spherical shape Rocky composition Small mass and radius
What processes are involved in the accretion of grains and gases to form planetesimals?
Static electrical charges Collisions Gravity
What can tell from the spectrum of a planet?
The composition of the atmosphere or the surface, if there is no atmosphere
The Jovian worlds grew more rapidly and larger than their terrestrial counterparts and have thicker atmospheres. What factor(s) allowed this to happen?
The larger protoplanets had a higher escape velocity. There were additional condensed materials to build planetesimals from. Gas particles at low temperatures move more slowly than those at high temperatures.
Which of the following are the same, or nearly the same, for the planets in our Solar System?
The plane of their orbits The direction they orbit The orientation of satellites' orbits around planets
Why do outer planets have deep atmospheres compared to the inner planets? (Select all that apply.)
Their atmospheres don't escape. Their stronger gravity allowed them to pull in hydrogen and helium. They were able to grow to much larger size because ammonia, water, and carbon compound ices were in the solar nebula in the outer Solar System.
According to the solar nebula theory, gas giants should form far from a star, where hydrogen-rich compounds can condense. How is it that we find gas giants orbiting very close to their parent star?
These giants formed far from their stars and migrated in.
Which of the following are planets in our Solar System?
Venus Saturn Uranus Mercury
The interstellar cloud that formed our Solar System was ____. (Select all that apply.)
a few light-years in diameter an enormous collection of gas and dust made mostly of hydrogen and helium
Compared to the Kuiper belt, the Oort cloud is ____. (Select all that apply.)
about 2000 times farther from the Sun more nearly spherical colder
This image shows an example of ____.
an interstellar cloud
A planet that orbits a star other than the Sun is called an _________.
exoplanet
You could characterize the arrangement of planets' orbital planes in the Solar System as basically ____.
flat
One type of observation astronomers have made that supports the solar nebula theory is of ____.
gas and dust disks in the Orion nebula
Young terrestrial planets were frequently melted by the kinetic energy of impacts with planetesimals This allowed denser materials (iron) to sink to their cores and less dense ones (rock) to rise. The source of this energy was _______ potential energy.
gravitational
Studying the atmosphere of a terrestrial planet, which gases would you expect to be rarest?
hydrogen helium
The Kuiper belt ____. (Select all that apply.)
is a broad region of space extending from Neptune's orbit out to 50 AU is home to dwarf planets such as Pluto, in addition to other icy bodies is similar to the asteroid belt, with mostly icy bodies rather than rocky ones is where some comets come from
The four giant planets contain substantial amounts of hydrogen and helium, whereas Earth or Mars don't, mostly because ____.
planets that formed in the outer Solar System could collect more mass (in the form of ice) early on and developed strong gravity
A comet would best be described as a ____.
small object made of ice and orbiting the Sun along a highly elliptical path
An asteroid would best be described as a ____.
small object made of rock and metal orbiting the Sun at a distance between 2 and 4 AU
The moons of Jupiter, Saturn, and Uranus all lie in flat planes oriented with the planet's equators. This is evidence that ____.
the moon systems formed with the planets like a smaller solar system
Uranus and Neptune differ from Jupiter and Saturn in that _____. (Select all that apply.)
they have a blue appearance they have substantial amounts of liquid water (ice giants)
Match the statements to explain the features of the graph of an exoplanet detection using the gravitational lensing method.
1. A: Relatively little light is seen when the exoplanet's host star is not aligned with the background star. 2. B: The exoplanet's host star crosses between us and the distant star and its gravity bends the distant star's light, magnifying it. 3. C: The exoplanet crosses between us and the distant star, and it magnifies the light from the distant star..
Organize the materials by the temperature at which they condense and can be incorporated into planets, from the ones that condense at the highest temperature (top) to the ones that condense at the lowest temperature (bottom).
1. Iron 2. Silicates 3. Water 4. Ammonia and methane
Model the formation of planets via accretion by placing the following steps in their correct order.
1. Iron, rock, and/or ice condense from the solar nebula 2. Flakes of condensed materials stick together by electrostatic forces 3. Smaller planetesimals collide and stick together. 4. Larger planetesimals are pulled together by gravitational forces.
Match each giant planet to its description.
1. Jupiter: The most massive gas giant. 2. Saturn: A gas giant with prominent rings. 3. Uranus: An ice giant. 4. Neptune: The farthest giant, also an ice giant.
Assess the relationship of each of the following to the Solar System.
1. Mars: A planet in the Solar System. 2. Polaris, the North Star: A star in our galaxy but not part of the Solar System. 3. Sun: The most massive object in the Solar System. 4. Milky Way Galaxy: Includes the Solar System.
Match the exoplanet feature with how it affects our ability to detect the planet.
1. Massive: Makes Doppler shifts in the star's spectrum bigger. 2. Far from the parent star: Takes more time to detect motion and find the period. 3. Orbital plane is face-on (perpendicular to the line of sight): Minimizes the Doppler effect and eliminates any chance of transits. 4. Large radius: Increases the probability and effect of transits.
Order the following planets from closest (top) to farthest (bottom) from the Sun.
1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter 6. Saturn 7. Uranus 8. Neptune
Place these planetary compositions in order of average density (lowest at the top):
1. Molecular hydrogen, helium, a small amount of water (Saturn). 2. Mostly water, with some rock and iron (Uranus). 3. Mostly rock and ice (Pluto). 4. Mostly rock, with a small amount of iron (Mars). 5. Mostly iron, with a small amount of rock (Mercury).
Match the atmosphere to the planet.
1. No atmosphere: Mercury 2. Nitrogen and oxygen: Earth 3. Carbon dioxide: Mars 4. Hydrogen and helium: Saturn 5. Hydrogen, helium, and methane: Neptune
Match the exoplanet detection method to the description.
1. Radical Velocity: We measure changes in the wavelength of the star's light due to its velocity in response to the planet. 2. Transit: We measure a decrease in the brightness of a star's light when a planet passes in front of the star 3. Direct Imaging: We take infrared images of a star and carefully subtract as much of the light of the star as possible to reveal any nearby glowing planets. 4. Gravitational Lensing: As a planet and star pass in front of a background star, we measure the increase in brightness of the background star.
Match the kind of planetesimal to its ultimate fate in the final stages of Solar System formation.
1. Rocky planetesimals disturbed by tidal forces from Jupiter: Asteroids in the asteroid belt 2. Icy planetesimals hurled away from the Sun by gravitational forces from the Jovian planets: Oort cloud comets 3. Rocky and/or icy planetesimals gravitationally captured by planets: Small satellites of Mars and the Jovian planets
Match the density with the type of material.
1. Silicate rock: About 3 g/cm3 2. Water or ice: About 1 g/cm3 3. Iron: About 7.9 g/cm3
Select the mechanisms that we think created the atmospheres of the terrestrial planets.
Comets and icy planetesimals hit the planets after they formed. Volcanoes outgassed materials such as water and carbon dioxide previously trapped in rock.
Select the mechanism that we think created the atmospheres of the Jovian planets.
Gravity allowed the planets to capture gas from the solar nebula.
Select all the choices that can be true of a comet.
Has a highly elliptical orbit Small icy body Has a diameter of about 10 km (6 miles)
A region between the orbit of Neptune (about 40 AU from the Sun) and 50 AU that contains mainly small, icy bodies on irregular orbits is called the _______ belt.
Kuiper
The image shows the result of what method of exoplanet detection?
Radial velocity
Match the average planetary density to either terrestrial or Jovian categories of planets.
Terrestrial: 3.9 g/cm3; 5.5 g/cm3 Jovian: 0.7 g/cm3; 1.6 g/cm3
Identify the true statements with regard to the direct imaging of exoplanets. (Select all that apply.)
The exoplanet is young. The exoplanet is a gas giant. The exoplanet is far from the star. Use an infrared telescope and camera.
We have detected many exoplanets, but we do not have many images of these planets. What is most prevalent reason why not?
The exoplanets are much dimmer than the stars. This makes them difficult to see.
What observations must be predicted by our model of the formation of the Solar System? (Select all that apply.)
The planets orbit the Sun in the same direction. Rocky planets are closer to the Sun, gaseous and icy ones farther out. The orbits of the planets are all approximately in the same plane.
Water is common in the universe, but it does not make up a major fraction of the inner planets. Why?
Water cannot condense close to the Sun, so it was not available.
A puzzling result of the discovery of exoplanets has been that in many other planetary systems ice and gas giants orbit closer to their stars than the _______ line beyond which they should have formed. One explanation is called planet _______, in which gravitational interactions between a planet and the protoplanetary disk alter a planet's orbit.
frost; migration
Cratered surfaces on Mercury or the Moon are evidence of impacts during the later stages of planet formation, when many of the planetesimals had been incorporated into planets, because ____.
impacts were far enough apart in time or space that the surfaces didn't melt enough to destroy the craters
One advantage of using gravitational lensing to detect exoplanets is that ____.
it can detect Earth mass exoplanets at a few AU from a star
Most satellites of the outer planets ____. (Select all that apply.)
orbit in the same direction their parent planet spins have density indicating a mixture of ice and rock
Anything that ____ is part of the Solar System.
orbits the Sun
