Chapter 11 Flashcards
rings (planetary)
The collections of numerous small particles orbiting a planet within its Roche tidal zone.
jovian nebulae
The clouds of gas that swirled around the jovian planets, from which the moons formed.
Io torus
A donut-shaped charged-particle belt around Jupiter that approximately traces Io’s orbit.
Galilean moons
The four moons of Jupiter that were discovered by Galileo: Io, Europa, Ganymede, and Callisto.
moonlets
Very small moons that orbit within the ring systems of jovian planets.
Cassini division
A large, dark gap in Saturn’s rings, visible through small telescopes on Earth.
metallic hydrogen
Hydrogen that is so compressed that the hydrogen atoms all share electrons and thereby take on properties of metals, such as conducting electricity. It occurs only under very high-pressure conditions, such as those found deep within Jupiter.
shepherd moons
Tiny moons within a planet’s ring system that help force particles into a narrow ring; a variation on gap moons.
gap moons
Tiny moons located within a gap in a planet’s ring system. The gravity of a gap moon helps clear the gap.
belts (on a jovian planet)
Dark bands of sinking air that encircle a jovian planet at a particular set of latitudes.
tidal heating
A source of internal heating created by tidal friction. It is particularly important for satellites with eccentric orbits such as Io and Europa.
orbital resonance
A situation in which one object’s orbital period is a simple ratio of another object’s period, such as 1/2, 1/4, or 5/3. In such cases, the two objects periodically line up with each other, and the extra gravitational attractions at these times can affect the objects’ orbits.
Great Red Spot
A large, high-pressure storm on Jupiter.
Roche tidal zone
The region within two to three planetary radii (of any planet) in which the tidal forces tugging an object apart become comparable to the gravitational forces holding it together; planetary rings are always found within the Roche tidal zone.
The energy in the atmospheres of most of the jovian planets comes ___________,
both the Sun and their interiors, in roughly equal proportions
Overall, Jupiter’s composition is most like that of ______.
the Sun (Both are made mostly of hydrogen and helium.)
How do typical wind speeds in Jupiter’s atmosphere compare to typical wind speeds on Earth?
They are much faster than hurricane winds on Earth.
What is the Great Red Spot?
a long-lived, high-pressure storm on Jupiter (It has been seen ever since telescopic observations of Jupiter began some 400 years ago.)
What atmospheric constituent is responsible for the blue color of Uranus and Neptune?
methane (The low temperatures of these distant planets allow for the formation of methane clouds that contribute to the blue color.)
How does the strength of Jupiter’s magnetic field compare to that of Earth’s magnetic field?
Jupiter’s magnetic field is about 20,000 times as strong as Earth’s.
Which moon has a thick atmosphere made mostly of nitrogen?
Titan
The Huygens probe took numerous pictures as it descended to Titan’s surface in 2005. What did the pictures show?
features or erosion, including what appeared to be dry river valleys and lakebeds (Titan is far too cold for liquid water, so these features probably were carved by liquid methane or ethane.)
Suppose you could float in space just a few meters above Saturn’s rings. What would you see as you looked down on the rings?
countless icy particles, ranging in size from dust grains to large boulders
Jupiter and the other jovian planets are sometimes called “gas giants.” In what sense is this term misleading?
They actually contain relatively little material in a gaseous state.
