Astronomy Chapter 11 - The Giant Planets

The planet that orbits "on its side" (i.e. has its rotation axis perpendicular to the plane of its orbit) is: a.Uranus b.Neptune c.Pluto d.Jupiter e.Saturn

Uranus

The element that can act like a metal when it is under tremendous pressure and is probably responsible for Jupiter and Saturn's magnetism is: a.gold b.helium c.hydrogen d.water e.vanallenium

hydrogen

The upper clouds in the atmosphere of Neptune are composed of: a.frozen water crystals b.liquid hydrogen c.iron crystals caught in the magnetic field lines d.carbon dioxide e.methane

methane

11.2 The Giant Planets

Jupiter is 318 times more massive than Earth. Saturn is about 25% as massive as Jupiter, and Uranus and Neptune are only 5% as massive. All four have deep atmospheres and opaque clouds, and all rotate quickly with periods from 10 to 17 hours. Jupiter and Saturn have extensive mantles of liquid hydrogen. Uranus and Neptune are depleted in hydrogen and helium relative to Jupiter and Saturn (and the Sun). Each giant planet has a core of "ice" and "rock" of about 10 Earth masses. Jupiter, Saturn, and Neptune have major internal heat sources, obtaining as much (or more) energy from their interiors as by radiation from the Sun. Uranus has no measurable internal heat. Jupiter has the strongest magnetic field and largest magnetosphere of any planet, first discovered by radio astronomers from observations of synchrotron radiation.

11.3 Atmospheres of the Giant Planets

The four giant planets have generally similar atmospheres, composed mostly of hydrogen and helium. Their atmospheres contain small quantities of methane and ammonia gas, both of which also condense to form clouds. Deeper (invisible) cloud layers consist of water and possibly ammonium hydrosulfide (Jupiter and Saturn) and hydrogen sulfide (Neptune). In the upper atmospheres, hydrocarbons and other trace compounds are produced by photochemistry. We do not know exactly what causes the colors in the clouds of Jupiter. Atmospheric motions on the giant planets are dominated by east-west circulation. Jupiter displays the most active cloud patterns, with Neptune second. Saturn is generally bland, in spite of its extremely high wind speeds, and Uranus is featureless (perhaps due to its lack of an internal heat source). Large storms (oval-shaped high-pressure systems such as the Great Red Spot on Jupiter and the Great Dark Spot on Neptune) can be found in some of the planet atmospheres.

11.1 Exploring the Outer Planets

The outer solar system contains the four giant planets: Jupiter, Saturn, Uranus, and Neptune. The gas giants Jupiter and Saturn have overall compositions similar to that of the Sun. These planets have been explored by the Pioneer, Voyager, Galileo, and Cassini spacecraft. Voyager 2, perhaps the most successful of all space-science missions, explored Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989)—a grand tour of the giant planets—and these flybys have been the only explorations to date of the ice giants Uranus and Neptune. The Galileo and Cassini missions were long-lived orbiters, and each also deployed an entry probe, one into Jupiter and one into Saturn's moon Titan.

The primary clouds in the atmospheres of Jupiter and Saturn are composed of: a.water vapor b.iron and nickel c.frozen ammonia crystals d.metallic hydrogen e.frozen alcohol 'ready to make cocktails'

frozen ammonia crystals

By far the most abundant element in the giant (jovian) planets is: a.helium b.hydrogen c.oxygen d.nitrogen e.silicon

hydrogen

What was a surprise to astronomers when they carefully examined Neptune with the Hubble Space Telescope in 1994? a.the magnetic field of the planet had reversed 'north was now south' b.new elements and compounds were found in the upper atmosphere that had not been there before c.the Great Dark Spot had disappeared d.the wind speeds had slowed considerably e.a large smiley-face had been constructed using dark clouds

the Great Dark Spot had disappeared

Which of the following does the composition of a planet like Jupiter resemble: a.the Sun b.the Moon c.the Earth d.Mars e.the asteroids

the Sun

What allowed the Voyager 2 spacecraft to make a "tour" of all four of the jovian planets in the late 1970's and the 1980's? a.NASA had developed a completely new kind of rocket that could send the craft from planet to planet b.the four planets were approximately aligned on one side of the Sun and we used the gravity of each planet to speed up the spacecraft to get to the next one in its path c.the spacecraft stopped off to collect fuel on the satellites of each planet before proceeding to the next one d.we used laser beams to propel the spacecraft into the outer solar system, where sunlight is dim e.you can't fool me, no spacecraft has ever explored four different planets

the four planets were approximately aligned on one side of the Sun and we used the gravity of each planet to speed up the spacecraft to get to the next one in its path

One reason that we have such a complex system of belts/zones/storms in Jupiter's atmosphere is that: a.the moon Io stirs up the atmosphere b.the planet rotates very rapidly c.the magnetic field is not centered inside d.ring particles "rain down" regularly e.the closeness of the asteroid belt means the planet feels a lot of gravitational tugs from nearby asteroids

the planet rotates very rapidly

At the moment when the Voyager spacecraft got closest to Uranus, the Sun was shining directly on the planet's south pole. Uranus takes about 17 hours to rotate once on its axis. If Voyager took a photo of the south pole 8.5 hours later, what would it observe? a.the south pole was in darkness b.the south pole was brightly lit, with the Sun shining down on it c.the south pole was in twilight d.the south pole was facing directly away from the Sun e.more than one of the other choices

the south pole was brightly lit, with the Sun shining down on it