AST 101 Exam 2 Orosz
The most likely formation mechanism for the solar system is that the a. Sun and planets slowly condensed to their present form from a gas and dust cloud. b. Sun captured the planets as they drifted through space. c. solar system was once a galaxy from which the Sun and planets are the remnants, after evolution. d. planets were spun out of the Sun as smaller gas clouds and subsequently condensed.
A
The nebular hypothesis of the formation of the solar system assumes that the material that became the solar system began as a large spherical cloud of gas and dust, rotating slowly. As the solar system formed, most of this material was transformed into a compact, flattened disk, rotating more rapidly. What is the explanation for this change in shape and rate of rotation? a. conservation of angular momentum. b. influence of nearby stars. c. differentiation of meterials easily vaporized and not easily vaporized. d. alignment with the plane of the Milky Way Galaxy.
A
The surface of Venus is best studied using a. radar. b. an Earth-based telescope. c. X-rays. d. visible light. e. infrared light.
A
What process formed the long underwater mountain range (the Mid-Atlantic Ridge) that extends along the center of the Atlantic Ocean? a. Solidification of molten lava from Earth's interior after being forced upward between two separating tectonic plates. b. Upthrusting caused by the collision of two separate tectonic plates on Earth's surface. c. Tidal forces when the Moon was much closer to the Earth than it is now. d. Erosion of the seabed by opposing deep ocean currents, southward on the west side and northward on the east, leaving the ridge between the two.
A
Which of the following categories of solar system objects does NOT include at least one dwarf planet? a. Oort cloud objects. b. asteroids. c. Kuiper belt objects. d. trans-Neptunian objects.
A
A meteor is a. an icy object in space, sometimes accompanied by a long, tenuous tail. b. a small, rocky or metallic object in orbit around the Sun. c. a flash of light as an object from space hurtles through our atmosphere. d. an object from space that has landed on the surface of the Earth.
C
Along a line where two tectonic plates collide, such as the North Pacific rim, you might expect to find each of the following except one. Which is the exception? a. subduction b. earthquakes c. seafloor spreading d. mount building e. volcanoes
C
The source of heating that melts the ice of a comet as it moves inward in the solar system is a. electric and magnetic currents produced in the comet by its interaction with the solar magnetic field. b. frictional heating as the comet moves through the interplanetary medium and the solar wind. c. intense solar radiation. d. tidal distortion of the comet's nucleus by the opposing gravitational forces from the Sun and the major planets, particularly Jupiter.
C
Titan, the largest moon of Saturn, is able to maintain an atmosphere because a. volcanoes continuously resupply gases that evaporate into space. b. cometary bombardment replenishes gases that evaporate into space. c. it has a relatively large mass and surface gravity, and its atmospheric temperature is low. d. it is rotating very slowly and is rather small.
C
What process had the greatest influence on the features of the Moon during the first billion years of its existence? a. erosion by an early, short-lived atmosphere b. volcanoes c. impacts from space d. mountain-building from geological activity
C
Why is it that terrestrial planets are thought to have dense iron cores? a. Thermonuclear reactions produced iron as a fusion product in the earlier phases of planetary evolution (e.g. thermonuclear accretion). b. During the formation of the planets, heavy elements accumulated first, followed by the accretion of lighter elements onto them (e.g. bomodal accretion). c. The planets were molten early in their life, and the heavy elements sank and lighter materials floated to the surface (e.g. planetary differentiation). d. Magnetism in the iron was sufficiently powerful to pull iron atoms to the center as the planet formed (e.g. magnetic sorting).
C
Earth and Mars are very similar planets in many ways. Which of the following pairs of physical charac- teristics are most alike for these planets? a. Overall mass and diameter b. Planet diameter and inclination of spin axis to the ecliptic plane c. Length of solar day and diameter d. Length of solar day and inclination of spin axis to the ecliptic plane
D
How was the mass of Pluto accurately determined? a. By measuring its apparent brightness (as seen from Earth). b. By measuring its average density. c. By measuring the effect of its gravity on Jupiter and Saturn. d. By measuring the orbit of one of its moons Charon. e. By observing its effect on the motion of an unmanned space probe that went near Pluto.
D
Neptune was discovered a. by accident while an astronomer was looking for comets. b. in antiquity, but it moves so slowly that people did not realize it was a planet. c. as it passed in front of a distant and bright star, blocking its light. d. by looking at a position on the sky predicted by calculations.
D
The San Andreas fault in California is an example of a. two tectonic planets pushing directly against one another. b. an upthrust due to a hot spot in the Earth's mantle. c. a spreading center, where two tectonic plates are being pushed away from each other. d. two tectonic plates sliding past each other.
D
The density of Pluto is about 2 grams per cubic centimeter, and its mass is 1/500 that of the Earth's mass. From this we conclude that a. Pluto has an iron core. b. Pluto is composed mostly of gaseous material. c. Pluto is composed almost entirely of water ice. d. Pluto is composed of a mixture of rocky material and water ice. e. Pluto is composed mostly of rocky material.
D
The heat energy in the interior of the Earth is due to a. gravitational contraction. b. chemical reactions. c. the Earth's magnetic field. d. natural radioactivity.
D
The moving plates on the Earth's surface a. have boundaries that are easily traced by only the study of seismic waves. b. are powered by the tidal pull of the Moon. If the Earth did not have a moon, it would not have plate tectonics. c. have boundaries that are mainly found on land and not in the oceans. d. have boundaries clearly mapped out by the locations of earthquakes and volcanoes.
D
The surface of Europa shows evidence of geologic activity. What is believed to be the source of the energy for this activity? a. gravitational energy released in the Kelvin-Helmholtz contraction. b. tidal forces from other nearby satellites, in particular Io, Ganymede, and Callisto. c. residual heat left over from its formation. d. tidal forces from Jupiter.
D
The word albedo refers to the a. fraction of the surface or atmosphere of a planet that is covered by cloud. b. ratio of infrared radiation to visible radiation emitted by a planet or other object. c. amount of light absorbed by a planet or other object. d. amount of light reflected by a planet or other object.
D
What is the typical distance between asteroids in the asteroid belt? a. 6000 km b. 1.2 Astronomical Units c. 25 km d. 1 to 10 million km
D
______________is by far the largest and most massive planet in the solar system.
Jupiter
Pluto, recently reclassified as a dwarf planet, is one of the larger known objects in the ____________belt.
Kuiper
Compared to the Earth, the atmosphere of Venus has a lot more a. carbon dioxide. b. oxygen. c. nitrogen. d. water vapor.
A
Do either of a comet's tails ever point towards the Sun? a. No. Comet tails must always point away from the Sun. b. Yes. The gas tail can point towards the Sun at times. c. Yes. Both the dust and gas tails can point towards the Sun at times. d. Yes, but it depends on the comet. e. Yes. The dust tail can point towards the Sun at times.
A
Some of the following features of the solar system overlap. But which objects, on average, are farthest from the Sun? a. Oort cloud objects. b. Kuiper belt objects. c. trans-Neptunian objects. d. planets. e. plutinos.
A
The asteroid belt formed in part because a. Jupiter's gravity prevented the asteroids there from coalescing into a planet. b. the protoplanet originally there broke up into fragments. c. Mars one orbited at that distance and stirred or churned it up, prevent accretion into a planet. d. The temperature at that distance was too cold for asteroids to stick together when they hit.
A
The average density of a planet is a. its total mass divided by its total volume. b. the amount of mass in unit volume of the material on its surface. c. another way of describing its total mass. d. the mass of a unit volume (1 cubic meter) of the material at its core.
A
Give a definition of "planet". What are the two main types of planets found in our solar system? Explain why these two types of planets are different, and give at least one example (e.g. the name) of each type.
A planet is a spherical body that orbits the Sun directly (that is it is not a satellite). There are a total of 8 planets in the solar system. 4 innermost planets are the so-called ''terresterial'' planets (Mercury, Venus, Earth, Mars). They have high densities and are mixtures of rock and metal. The so-called ''Jovian'' or Jupiter-like planets are massive and large. However, they have low densities and are composed of gases such as methane and ammonia and hydrogen. Jupiter, Saturn, Uranus and Neptune are examples.
Jupiter is composed mainly of a. iron and rocky material. b. hydrogen and methane. c. carbon dioxide. d. water ice.
B
Kuiper belt objects are a. the remains of comets that have been "burned up" by the Sun. b. dark icy objects with orbits beyond that of Neptune. c. objects with orbits that cross the Earth's orbit. d. all of the above e. none of the above.
B
The most common elements in the universe are a. about equal amounts of all elements up to iron but very little of any heavier elements. b. hydrogen and helium, with small amounts of heavier elements. c. nitrogen and oxygen, with smaller quantities of hydrogen, helium, and heavier elements. d. heavy elements, with smaller quantites of hydrogen and helium.
B
The reason tides occur on Earth is that the a. the rotation of the Earth makes the water "slosh" around. b. gravitational force exerted on Earth by the Moon decreases with increasing distance from the Moon. c. gravitational forces of the Sun and the Moon on Earth sometimes act together and sometimes cancel each other. d. gravitational force exerted on the Moon by Earth decreases with increasing distance from Earth. e. Moon exerts a gravitational force on Earth, pulling the water into a bulge on one side of Earth.
B
There is very little hydrogen or helium in the inner part of the solar system today. We believe the reason for this is that a. all the light elements went into the formation of the Sun itself and little were left over for the rest of the solar system. b. the intense radiation from the early Sun drove the light elements out of the inner solar system. c. heavier elements were attracted in from the outer part of the solar system, displacing the light elements originally in the inner part. d. the light elements underwent chemical reactions and were locked up in chemicals in the inner solar system.
B
What conclusion can you draw when you compare the density of materials found on Earth's surface (about 3 grams/cm3) with the density of Earth as a whole (about 5.4 grams/cm3)? a. The Earth is remarkably uniform throughout. b. The interior of the Earth must contain materials like iron and nickel. c. The Earth's interior is hollow. d. The Earth's interior is molten.
B
Which is the most abundant gas in the Earth's atmosphere? a. oxygen b. nitrogen c. hydrogen d. carbon dioxide
B
Most of the asteroids in the solar system have orbits between_____________and _______________.
mars, jupiter
The surface of Mercury resembles that of the _____________.
moon
The protosun became the Sun after ______________started to occur in its core.
nuclear fusion
________________pass through the Earth, and are used to study the Earth's interior.
seismic waves
Mercury, Venus, Earth, and Mars are referred to as _______________planets.
terrestrial
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Multiple Choice
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Short Answers
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On the Moon, a "mare" is a(n) a. area of bright streaks, or rays, extending outward from a relatively young crater. b. a large body of water. c. heavily cratered region in the lunar highlands. d. pattern of large craters. e. lava floodplain covering the floor of an ancient asteroid impact basin.
E
The surface of Mercury most resembles the surface of a. Mars. b. Jupiter. c. Venus. d. The Earth. e. The Moon.
E
Give three classes of small solar system bodies (e.g. name them) other than satellites. For each class, state generally where in the Solar System one can find those objects, and briefly describe a typical body from that class. Give a proper name for one object out of two of the class for one bonus point.
The three classes of solar system objects are: • asteroids: These are small rocky bodies that have orbits mainly between Mars and Jupiter. Only a few asteroids are larger than 1000 km. Ceres is the largest body in the asteroid belt. Recently this object has been reclassfied as a dwarf planet. • Kuiper Belt Objects: These are small icy bodies that orbit mainly outside the orbit of Neptune up to about 50 astronomical units from the Sun. Like the asteroids, only a few of the known Kuiper belt objects are larger than about 1000 km. A few of them are classified as dwarf planets; Pluto and Eris are two such examples. • comets: Most of the comets are in the Oort comet cloud, which is a roughly spherical region that extends up to about 10,000 astronomical units from the Sun. The comets are small, icy bodies with typical sizes of a few dozen km. Some of the comets have been disturbed and sent into orbits that take them much closer to the Sun. Hally's comet is one such example. When the comets get near the Sun, the intense radiation from the Sun starts to vaporizae the ices on the surface of the comet. This produces a fairly large region of glowing gas that is called the coma. Also, the intense solar radiation drives off dust and gasses that form a comet ''tail''. These tails can be up to 100 million km long, and they always point away from the Sun.
2. Give two ways planets around other stars can be found using currently available technology. For each technique, explain how it works and what quantity is measured. Draw diagrams to support your answers.
There are 4 ways that planets around other stars can be found: • Radial velocity method: When a star has planets in orbit about it, it will ''wobble'' slightly since the star actually orbits the center of mass of the system. This will cause the radial velocity of the star to change slightly over time in a periodic way. If high resolution spectra can be obtained, then one could measure a change in the Doppler shifts of the spectral lines. • Astrometric method: Similar to above, a star will ''wobble'' about the center of mass of the system. If the star has a motion in the plane of the sky (the so-called ''proper motion''), then this wobbling motion can in principle be measured. One simply measures very precise positions of the star over time. However, in most cases, this wobbling motion is too small to measure. • Transit method: If a star has a planet in orbit about it, then that planet could pass between us and its parent star if the orbit has the correct orientation. If this happens, and little bit of the light from the star will be blocked for a few to several hours. If we can measure very precisely the brightness of a star over time, then such transit events can be indentified. • Gravitational microlensing: If two stars line up very precisely as seen from Earth, and if the distance between the stars is fairly large, then the light from the star in the back can be magnified by the star that is in between. If one measures the brightness over time of the star in the back, then one may see a brief spike in the brightness. Furthermore, if the star in between has a planet, then that planet could also magnifythe light from the star in the back, again provided that the alignment of the Earth, planet, and distant star is precise.
Outline the technique that is used to determine the age of the Moon and of the solar system.
We use a technique called ''radioactive dating''. Radioactive isotopes (the ''parent'' isotopes) will decay spontaneously and end up as different isotopes (the ''daughter'' isotopes). The rate at which the radioactive isotopes decay is related to a quantity called the ''half life,'' which is the time needed for half of a given sample to decay. If one measures very carefully the abundance of various elements in a rock sample, then one can figure out the age of that sample. One measures the ratios of various parent/daughter combinations. When one knows the various half lives of each parent isotope, then the ratios of parent/daughter elements gives the age. For example, if a rock is very old, very few atoms of the parent isotopes will be left, whereas the daughter isotopes will be somewhat abundant.
The Earth's ______________keeps it about 30◦ C warmer than it would have been otherwise.
atmosphere
Based on its low _____________, astronomers infer that Saturn is composed mostly of light elements such as hydrogen and helium.
density
The exceptionally high surface temperature of Venus is caused by an "runaway" ____________
greenhouse affect
