Astro 103 Chapter 12

Who was the first person to report seeing the rings of Saturn although he did not realize that they were rings? A. Johannes Kepler B. Galileo Galilei C. Christiaan Huygens D. We do not know—the rings have been known since ancient times.

B. Galileo Galilei

Evidence of volcanism (lava outflow, etc.), either active or ancient, is not found on A. Venus. B. Jupiter. C. Earth. D. Mars.

B. Jupiter.

Suppose Mimas orbited further out from Saturn than it does now. What differ-ence, if any, would this make to the Cassini division? A. The orbit of Mimas has no effect on the Cassini division. B. The Cassini division would also move further out. C. The Cassini division would disappear (fill in with ring particles) and not re-form else-where. D. The Cassini division would move inward toward Saturn.

B. The Cassini division would also move further out.

The Roche limit around a planet is defined as A. the distance inside which a solid satellite (e.g., a fragment of rock) will be pulled apart by tidal forces. B. the distance beyond which the orbital velocity of a body in a Keplerian orbit is greater than the escape velocity and matter is no longer captured by the planet. C. the distance inside which relative tidal forces will overcome the mutual gravitational forces of a group of particles. D. the outer extent of the magnetic field of the planet, or the magnetospheric boundary.

C. the distance inside which relative tidal forces will overcome the mutual gravitational forces of a group of particles

The particles in Saturn's rings are composed of A. a mixture of iron and nickel. B. rocks with the reflectivity of dark asphalt. C. water ice or rock coated with water ice. D. ammonia and methane ice, possibly with rocky centers.

C. water ice or rock coated with water ice.

How do we know the nature of the brown ovals in Jupiter's atmosphere? A. The brown color matches other features at that level, so we know they form a continuous part of that atmospheric layer. B. They glow brightly in infrared, thus we know they are holes in the atmosphere that allow the escape of infrared from warmer, deeper layers. C. They glow brightly in infrared, thus we know they are warm, high-altitude clouds. D. They glow dimly in infrared, thus we know they are actually at higher, colder levels in the atmosphere.

B. They glow brightly in infrared, thus we know they are holes in the atmosphere that allow the escape of infrared from warmer, deeper layers.

The ring of material that surrounds Jupiter appears to be made up of A. gas vapor of individual molecules of hydrogen sulfide and sulfur dioxide from Io's vol-canoes. B. extremely fine dust particles, about the size of smoke particles, of average diameter 1/1000 mm. C. pure ice crystals, similar to those in high cirrus clouds on Earth. D. icy, reflective rocks, averaging about 1 cm in diameter but with wide variation in size.

B. extremely fine dust particles, about the size of smoke particles, of average diameter 1/1000 mm.

Jupiter's Great Red Spot A. has changed color dramatically more than once, becoming white or brown. B. has changed its size significantly during the past three and a half centuries. C. has remained virtually unchanged during the three and a half centuries it has been ob-served. D. has disappeared (for decades at a time) and then re-emerged several times in the past three and a half centuries.

B. has changed its size significantly during the past three and a half centuries.

The reason for the slightly flattened or oblate shape of Jupiter is A. its cloud cover, more clouds forming over the equator on average. B. its rapid rotation rate. C. the gravitational pull of the Sun and the other planets in the ecliptic. D. that it was formed that way in the beginning and has maintained this shape.

B. its rapid rotation rate

The interesting feature of Jupiter's rotation is that A. its axis of rotation lies almost in the plane of its orbit. B. regions at different latitudes appear to rotate at different rates. C. it rotates in a direction opposite to that of most of the planets and opposite to its direction of revolution around the Sun. D. its rotation rate has slowed down significantly since it was first observed through tele-scopes in the 1600s.

B. regions at different latitudes appear to rotate at different rates.

Jupiter's ring was discovered by A. visual observations by Galileo. B. spacecraft photography. C. direct, ground-based photography. D. momentary occultation of starlight as the planet and the rings moved in front of a star.

B. spacecraft photography.

The large-scale atmospheric circulation pattern on Jupiter is characterized pre-dominantly by A. isolated cyclones (low-pressure areas) and anticyclones (high-pressure areas), as on Earth. B. strong winds blowing parallel to the equator but in opposite directions at different latitudes. C. strong winds blowing eastward at all latitudes so that the entire atmosphere rotates faster than the planet. D. strong winds blowing westward at all latitudes so that the entire atmosphere rotates more slowly.

B. strong winds blowing parallel to the equator but in opposite directions at different latitudes.

The reason why boulder-sized moonlets are able to orbit within the Roche limit in Saturn's rings without being destroyed is that A. the gravitational forces between the different parts of the moonlet are greater than the tidal forces pulling them apart. B. the chemical bonds between their atoms and molecules are greater than the tidal forces pull-ing them apart. C. they are too small for tidal forces to operate on them effectively. D. billions of years of alternate freezing and thawing as they pass from sunlight into Saturn's shadow and out again has given them an iron-hard crust of ice.

B. the chemical bonds between their atoms and molecules are greater than the tidal forces pull-ing them apart.

The major gaps in the rings of Saturn are most likely caused by A. the intervention of a massive body, which moved through the rings in their early history, leaving the gaps. B. the combined gravitational forces of Saturn and its major moons, which deflect the paths of particles that stray into the gaps. C. mutual gravitational interactions between the multitude of particles in the rings. D. the major moons of Saturn, which move in these gaps and sweep out the ring material.

B. the combined gravitational forces of Saturn and its major moons, which deflect the paths of particles that stray into the gaps.

No heavy materials (iron, nickel, etc.) have been found in the atmosphere of Ju-piter. This is because A. there were no heavy materials in that part of the solar system where Jupiter was formed. B. they have sunk to the center. C. they have evaporated away. D. of impacts early in the history of the solar system that ejected these materials to form satellites.

B. they have sunk to the center.

The rotation periods for the Jovian planets—Jupiter, Saturn, Uranus, and Nep-tune—are A. reasonably long—on the order of several Earth days. B. very short—about 10 to 20 hours. C. very long—on the order of years because of the sizes. D. very short—between 1 and 2 hours.

B. very short—about 10 to 20 hours.

How was the Cassini division created in Saturn's rings? A. A small moon orbited within the division, clearing particles from the gap. B. The rings simply formed that way in the ancient past. C. One of Saturn's satellites exerted a resonant pull on particles in the division, clearing a gap. D. An intense region of high-energy electrons in Saturn's magnetosphere at that distance eroded the particles from the gap.

C. One of Saturn's satellites exerted a resonant pull on particles in the division, clearing a gap.

Saturn's magnetosphere contains many fewer charged particles than does Jupiter's magne-to-sphere. Which one of the following is not part of the reason for this difference? A. Saturn does not have a geologically active satellite within its magnetosphere. B. Saturn has a smaller magnetic field than does Jupiter. C. Saturn has a much slower rotation rate than Jupiter. D. Saturn's rings absorb charged particles.

C. Saturn has a much slower rotation rate than Jupiter.

Other than the rings, how does the appearance of Saturn differ from that of Jupi-ter? A. Saturn has many more belts and zones than Jupiter, with large storms distorting their shapes. B. Saturn's visible surface is basically featureless, with no hint of the belts and zones of Jupiter. C. There are belts and zones on Saturn, but they are very faint and hazy compared to Jupiter's. D. Saturn shows an ever-changing system of dark storms and light eddies, without the belts and zones of Jupiter.

C. There are belts and zones on Saturn, but they are very faint and hazy compared to Jupiter's.

The Cassini division is A. a gap between two groups of asteroids in the asteroid belt. B. the division between terrestrial and Jovian planets. C. a major division in the rings of Saturn that is visible from Earth. D. a gap between two mountain ranges on the Moon.

C. a major division in the rings of Saturn that is visible from Earth.

Rings of dust and icy particles are found around which planets? A. all four of the terrestrial planets B. only Saturn C. all four of the Jovian planets D. all planets that have moons associated with them

C. all four of the Jovian planets

The rings of Saturn are composed of very many small particles because they A. are made up of ice and ice-coated rocks, which break up easily in sunlight. B. were spun out of the planet under its rapid rotation over a long period of time. C. are inside the Roche limit of Saturn, where tidal forces are stronger than the mutual grav-itational forces between particles. D. were formed by the impact of a fast-moving asteroid on a large moon, which broke up into very many pieces.

C. are inside the Roche limit of Saturn, where tidal forces are stronger than the mutual grav-itational forces between particles.

Saturn appears to emit heat as infrared radiation in excess of the energy absorbed from sun-light and also the Kelvin-Helmholtz Contraction. The most likely major cause of this excess heating is A. the radioactive decay of naturally occurring isotopes in the atmosphere and interior of Saturn. B. remnant heat from the original formation of the planet. C. energy released from the continuous shrinking and condensation of this fluid planet. D. the condensing of helium into droplets that fall into the planet, releasing gravitational energy as heat.

D. the condensing of helium into droplets that fall into the planet, releasing gravitational en-ergy as heat.

What is the Cassini division? A. the boundary between the bright B ring and the faint C ring in Saturn's rings. B. a major gap in the asteroid belt. C. the layer of relatively clear air separating Saturn's upper cloud deck from the middle cloud deck. D. a wide, dark gap in Saturn's rings.

D. a wide, dark gap in Saturn's rings.

The presence of helium in the atmosphere of Jupiter was first established by A. precise spectrophotometry of infrared emission lines of helium from Earth. B. direct sampling of Jupiter's atmosphere by the Galileo Probe. C. detection of weak absorption bands of molecular helium by the Ulysses spacecraft. D. careful observation of the spectrum of hydrogen by spacecraft.

D. careful observation of the spectrum of hydrogen by spacecraft.

What conditions are considered necessary for a planet to be able to generate an intense mag-netic field? A. solid iron core into which a magnetic field was induced early in the planet's history B. electrically conducting material in its interior and slow rotation, because rapid rotation will destroy a magnetic field C. ionized and electrically conducting layer in its atmosphere D. relatively rapid rotation and electrically conducting material in its interior

D. relatively rapid rotation and electrically conducting material in its interior

The white ovals seen on Jupiter appear to be A. clouds of ammonia ice crystals that condense when Jupiter's atmosphere flows over fixed obstacles such as mountains. B. upwelling gas that then descends in the brown ovals. C. descending masses of gas within the dark belts. D. vortices (whirlpools) created between regions of oppositely directed winds.

D. vortices (whirlpools) created between regions of oppositely directed winds.

A spacecraft is moving directly toward a large planet, and a rock rests on the side of the craft nearest the planet, held only by its gravitational attraction to the craft. As the planet is ap-proached, we will observe A. that at a certain distance the rock will be forced into an orbit around the planet. The space-craft will remain intact. B. no change. The spacecraft and rock will remain together. C. that at a certain distance the rock will begin to accelerate toward the planet. The space-craft will be left behind, but it will remain intact. D. that at a certain distance tidal forces will pull the rock off the craft and also destroy the craft.

C. that at a certain distance the rock will begin to accelerate toward the planet. The space-craft will be left behind, but it will remain intact.

Jupiter and Saturn each have the same three basic cloud layers, but the spacing of the layers differs on the two planets. Why is this? A. Jupiter's greater gravity has compressed the layers, so they are closer together there. B. Jupiter's greater rotation rate has flung the layers outward, so they are separated more there. C. Jupiter's warmer temperature has expanded the atmosphere, so they are more separated there. D. On Saturn, the "rain" of helium condensate has forced the lower layers downward, so they are more separated there.

A. Jupiter's greater gravity has compressed the layers, so they are closer together there.

Why do the rings of Saturn alternately appear very distinct and then almost dis-appear when viewed from Earth over periods of a few years? A. The plane of the rings is tilted with respect to the ecliptic plane and thus appear edge-on at times. B. Earth is very much closer to Saturn at opposition than at conjunction; hence the rings are more easily seen at this time. C. The ice crystals from which they are made melt and refreeze as the planet approaches and recedes from the Sun. D. The solar wind occasionally blows away the ring particles when the Sun is particularly active.

A. The plane of the rings is tilted with respect to the ecliptic plane and thus appear edge-on at times.

Saturn is less massive than Jupiter but has almost the same size. Why is this? A. The smaller mass exerts less gravitational force and is unable to compress the mass as much as in Jupiter. B. Saturn's interior is hotter than that of Jupiter. C. Saturn is rotating faster than Jupiter, and the increased centrifugal force results in a larger size. D. Saturn is composed of lighter material than is Jupiter.

A. The smaller mass exerts less gravitational force and is unable to compress the mass as much as in Jupiter.

Assuming all objects listed are visible, on a clear, moonless night the brightest object in the sky is A. Venus. B. Jupiter. C. Saturn. D. Sirius.

A. Venus.

The high-speed winds observed on Jupiter occur mainly A. at the boundaries between the dark belts and the light zones. B. near the centers of the dark belts. C. in a north-south direction from the dark belts toward the light zones. D. near the centers of the light zones.

A. at the boundaries between the dark belts and the light zones.

The darker-colored bands that encircle the high atmosphere of Jupiter and are visible through telescopes from Earth are known as A. belts. B. white spots. C. rings. D. zones.

A. belts.

The circulation pattern in and around the Great Red Spot on Jupiter is A. counterclockwise between two sets of winds flowing in opposite directions. B. outward (away from Jupiter's center) inside the Great Red Spot and back down (into Jupiter's interior) outside it, like a convection cell. C. clockwise between two sets of winds flowing in the same direction but with different speeds. D. from west to east, rising and falling like air flowing over a mountain.

A. counterclockwise between two sets of winds flowing in opposite directions.

The source of excess heat emitted by Jupiter, above that which is absorbed as sunlight and reemitted, is thought to be A. gravitational potential energy released as heat during its formation stages, still being re-leased. B. heat caused by friction between oppositely directed winds at mid-latitudes. C. heat generated in the interior by the same electrical currents that generate the planet's mag-netic field. D. chemical reactions between methane, ammonia, and water in the planet's atmosphere and clouds.

A. gravitational potential energy released as heat during its formation stages, still being re-leased.

The deepest central cores of the interiors of Jupiter and Saturn are thought to be composed of A. rock. B. methane, ammonia, and water vapor. C. magnetized iron. D. liquid metallic hydrogen

A. rock.

How does the composition of Saturn's atmosphere compare to that of Jupiter, which is the same as that of the Sun? A. They are almost equivalent, with the same proportions of hydrogen, helium, and heavier ele-ments. B. Saturn's atmosphere has far less hydrogen than does that of either Jupiter or the Sun. C. Saturn's atmosphere contains far more heavy elements than does that of either Jupiter or the Sun. D. Saturn's atmosphere contains less helium than does that of either Jupiter or the Sun.

D. Saturn's atmosphere contains less helium than does that of either Jupiter or the Sun.

The Saturnian satellite Pan moves along the Encke gap. Suppose a rock is or-biting within the gap at an orbital radius slightly smaller than that of Pan. Which one of the following is a correct description of the interaction between Pan and the rock? A. The rock catches up to and passes Pan. As it does so Pan pulls itself forward, making it move faster and causing it to move into an orbit with a larger radius. B. Pan catches up to and passes the rock. As it does so it pulls back on the rock, slowing it and causing it to move in an orbit with a smaller radius. C. Pan catches up to and passes the rock. As it does so it pulls back on the rock, slowing it and causing it to move in an orbit with a larger radius. D. The rock catches up to and passes Pan. As it does so Pan pulls itself forward, making it move faster and causing it to move into an orbit with a smaller radius.

D. The rock catches up to and passes Pan. As it does so Pan pulls itself forward, making it move faster and causing it to move into an orbit with a smaller radius.

Why is the F ring much narrower than the main rings? A. The ring is constrained by Saturn's strong magnetic field. B. The ring is in a stronger part of Saturn's gravitational field and cannot spread out any farther. C. There are not enough particles available to make a wider ring. D. Two "shepherd" satellites focus the particles into a narrow ring.

D. Two "shepherd" satellites focus the particles into a narrow ring.