Astronomy Exam 4

The surface of Europa, one of Jupiter's Galilean satellites, is characterized by

A fractured crust of ice with evidence of ice rafts and areas of flooding at some earlier time.

Hydrogen is normally a gas, but we say that the hydrogen in the interior of Jupiter is "metallic" because it is

A good conductor of electricity.

One surprising result of recent observations of asteroids by radar and by spacecraft exploration is that most asteroids of greater than about 1 km in diameter consist of

A loose collection of smaller, interplanetary "rubble."

What is the difference between a meteoroid, a meteor, and a meteorite?

A meteoroid is a small solid object orbiting the Sun. A meteor is the flash of light in the sky when a meteoroid burns up in the atmosphere. A meteorite is a fragment of the original meteoroid that survives the fall through the atmosphere and reaches the ground.

Which one of the following statements about asteroids is false?

Asteroids are a significant hazard to spacecraft passing through the asteroid belt.

As of this writing (2007), how many satellites for Jupiter are known?

Between 60 and 70

How was Uranus discovered?

By accident, by an astronomer conducting a sky survey

Near Earth Objects, or NEOs, are

Capable of creating a life-threatening impact every few tens of millions of years or so.

Compared to Earth, Jupiter, and Saturn, the magnetic fields of Uranus and Neptune

Have axes tilted a long way from the spin axis of the planets.

What is the significance of the Roche Limit for a planet?

It is the minimum distance at which a moon can orbit a planet without being torn apart.

Suppose an asteroid fragment of typical size is heading straight for the Earth. What will be the expected result?

The fragment will burn up in our atmosphere.

Which of the following statements is true about Jupiter but not about Saturn?

The planet is more dense than water (1000 kg/m3).

Where are the majority of the asteroids, or minor planets, found in the solar system?

In a broad region between the orbits of Mars and Jupiter

What is liquid metallic hydrogen?

In liquid metallic hydrogen, hydrogen atoms form a crystal lattice. Electrons can flow from one part of the lattice to another, as happens in an ordinary metal.

The surfaces of asteroids are generally

Covered with rubble and small craters.

Which Jovian satellite that is thought to have an ocean of liquid water beneath an icy crust?

Europa

The surface of Europa shows evidence of geologic activity. What is believed to be the source of the energy for this activity?

Tidal forces from Jupiter

The rings of Saturn are seen by

Reflected and scattered sunlight.

Most of the meteoric material falling onto the Earth from space is composed of

Stony material.

Rings of dust and icy particles are found around which planets?

All four of the Jovian planets.

Which of the following biochemical materials has been found and identified in rocks recovered from outer space (e.g., meteorites)?

Amino acids

How big is the planet Uranus?

Considerably bigger in diameter and mass than the Earth but much smaller in both respects than Saturn

What is the cause of the immense magnetic fields of Jupiter and Saturn?

Electric currents in the region outside the planet's core, deep below the atmosphere.

What aspects of Europa lead scientists to speculate that life may exist there?

Europa may have oceans of liquid water under its surface.

The ring of material that surrounds Jupiter appears to be made up of

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

10. Shepherd satellites continually disrupt Saturn's rings, causing them to disappear and later reform.

False.

Saturn's moon Titan has a size

Intermediate between Mercury and Mars.

Neptune emits more energy into space than it receives from the Sun, whereas Uranus does not. What visible effect does this have on the appearance of Neptune compared to that of Uranus?

It causes cyclones and high-altitude ice clouds on Neptune, compared to an almost featureless appearance of Uranus.

Jupiter is the largest planet in our solar system. What is Jupiter's mass compared with that of the rest of the planets?

Jupiter contains 71% of the mass of all the planets

How does the visual appearance of Saturn compare with that of Jupiter, excluding the differences in the rings?

Jupiter has an extensive and intricate cloud system of belts, zones, storms, and eddies, whereas Saturn's features appear very subdued and hazy.

The asteroid belt formed in part because

Jupiter's gravity prevented the asteroids there from coalescing into a planet.

What are the physical characteristics of the "other" (non-Galilean) satellites of Jupiter?

Less than about 200 km in diameter and irregular in shape

What is the significance of liquid metallic hydrogen for Jupiter?

Liquid metallic hydrogen forms only at enormous pressure, and this occurs only in interiors of Jovian planets. It is the electrical conductor which produces Jupiter's large magnetic field.

Four of the moons of Saturn are

Mimas, Enceladus, Titan, and Dione.

When compared to other objects in the solar system, the Galilean satellites of Jupiter are about the size of

Our Moon or a bit larger.

What observational facts lead to the conclusion that the small outer moons of Jupiter were captured by its gravitational field rather than being formed at the same time as the planet?

They move in orbits that are steeply inclined to Jupiter's equator, many of them in a retrograde direction, opposite to Jupiter's rotation.

Which statement correctly describes our understanding of the magnetic fields on Uranus and Neptune?

They originate in the motion of underground oceans of a water-salt-ammonia mixture like the magnetic fields of some of the Galilean moons of Jupiter.

One interesting feature of the motions of the giant planets that distinguishes them from the terrestrial planets is that

They rotate more rapidly than either Mars or Earth.

Most of Saturn's rings lie inside of Saturn's Roche Limit.

True.

The amount of heat that Jupiter radiates into space is

Twice as much as it receives from the Sun, because it is still cooling down after the process of planetary formation.

Uranus has its rotation axis tilted almost in the plane of its orbital motion. What effect does this have on the seasons Uranus experiences?

Unlike the situation on Earth, the tilt of the axis of Uranus means that first one pole and then the other is pointed in the Sun's direction for a long period of time.

How do the densities of Jupiter, Saturn, Uranus, and Neptune compare?

Uranus and Neptune are more dense than Jupiter or Saturn.

Uranus and Neptune are substantially smaller than Jupiter and Saturn. Which is also considered a possible scenario for the formation of Uranus and Neptune that explain these size differences?

Uranus and Neptune formed at a location closer to the Sun and were then moved to their present hydrogen-and -helium-deficient region before they could accumulate much hydrogen and helium.

Enceladus, one of Saturn's icy moons, is unusual in the solar system because it has

Volcanic activity that ejects plumes of icy particles into space.

Neptune was discovered

While looking for the body whose gravity was affecting the orbit of Uranus.

Saturn's rings are composed of

Myriads of icy particles, ranging from dust grains to boulders, moving in Keplerian orbits in the planet's equatorial plane.

What is the structure of Saturn's rings?

Saturn's rings are composed of thousands of ringlets that are organized into the major rings.

What is the evidence that some asteroids are made of a loose conglomeration of smaller particles?

Some asteroids show large impact craters. Such an impact would have shattered a solid asteroid. But an asteroid that is a loose conglomeration held together by gravity would be able to absorb such an impact. The asteroid might come apart and then be pulled back together again.

What precautions have been taken to prevent contaminating Europa with Earth organisms?

The Galileo spacecraft was sent to a fiery death in the Jovian atmosphere to avoid contaminating the surface of Europa with Earth organisms.

The composition of the atmosphere of Jupiter is most similar to the composition of the atmosphere of

The Sun.

Why are Uranus and Neptune distinctly blue-green in color, whereas Jupiter and Saturn are not?

The atmospheres of both Uranus and Neptune contain substantial amounts of methane, whereas the atmospheres of Jupiter and Saturn do not. Methane absorbs the long wavelength part of the Sun's visible spectrum, allowing the blue and green to pass through.

What evidence is there that ring particles do not migrate significantly between ringlets?

The ring particles are not all the same color. Different colors are caused by chemicals, and they tend to segregate with different colors in different ringlets. These colors have remained constant, suggesting that particles do not migrate significantly between ringlets.

What is the probable origin of the other (non-Galilean) satellites of Jupiter?

The satellites inside the orbits of the Galilean satellites probably formed from the Jovian nebula. Those outside the orbits of the Galilean satellites are probably captured asteroids.

In general, how do the asteroids compare with the trans-Neptunian objects?

The trans-Neptunian objects are larger and have more ice and less rock.

Ganymede and Callisto, two of the Galilean satellites of Jupiter, have mean densities of about 1900 kg/m3. What does this tell us about the probable composition of these two satellites?

They are a mixture of roughly equal quantities of rock and ice.

The source of heat that drives the volcanic eruptions of sulfur and sulfur compounds on Io, the giant moon of Jupiter, is

Tidal distortion and flexing caused by gravitational effects from Jupiter and other moons.

Uranus and Neptune are substantially smaller than Jupiter and Saturn. Which of the following are considered possible scenarios for the formation of Uranus and Neptune that explain these size differences?

Uranus and Neptune formed at their present locations directly from condensation of the solar nebula. The excess hydrogen and helium was then taken away by ultraviolet radiation from a nearby hot star.

How (if at all) do the interiors of Uranus and Neptune differ from the biggest Jovian planets, Jupiter and Saturn?

Uranus and Neptune have a thick layer of water between the rocky core and the liquid hydrogen mantle, whereas Jupiter and Saturn are mostly liquid hydrogen.

The spacecraft that successfully photographed Neptune on a 1989 flyby mission was

Voyager