Astronomy Chapter 7

What are the characteristics of a Jovian planet?

large diameters (five or more times Earth), contain much hydrogen and helium, low average densities

Which of the following are among the seven giant satellites?

Ganymede, Io, titan, the moon, triton,

What is a Trans-Neptunian Object?

A Trans-Neptunian Object is a small body of rock and ice that orbits the Sun beyond the orbit of Neptune.

Which of the following best describes the orbits of the inner planets?

All of the planets orbit counterclockwise.

Which of the following best describes the orbits of the outer planets?

All of the planets orbit counterclockwise.

What is an asteroid?

An asteroid is a small rocky body orbiting the Sun in the inner part of the solar system. Asteroids are debris left over from the original formation of the solar system.

The surfaces of Mercury, the Moon, and Mars are riddled with craters formed by the impact of space debris. Many of these craters are billions of years old. By contrast, there are only a few conspicuous craters on Earth's surface, and these are generally less than 500 million years old. Why this difference?

Earth is a geologically active planet, and the surface also experiences erosion. Plate tectonics, in particular, have resurfaced the planet and removed the older craters. The other bodies have been geologically inactive for billions of years.

Which planet is moving fastest?

Jupiter

Mercury rotates once on its axis every 58.646 days, compared to one day for Earth. Based on this information, how would you expect Mercury's magnetic field to compare with Earth's magnetic field?

Magnetic fields in a body are produced by electric currents, which are created when the body rotates. The faster it rotates, the larger the current, and the stronger the magnetic field. So Earth's magnetic field is much larger than Mercury's.

Which planet has the longest year?

Mars

Which planet is moving fastest?

Mercury

Are all the planetary orbits circular?

Most of the planetary orbits are nearly circular.

Which planet has the longest year?

Neptune

They all lie extremely close to the plane of the ecliptic (the plane of Earth's orbit).

The solar system formed from a single rotating disk of gas and dust.

Which of the following best describes the planes of the planets' orbits?

They all lie extremely close to the plane of the ecliptic (the plane of Earth's orbit).

In what ways are asteroids and Trans-Neptunian Objects like and unlike planets?

They are both like planets in that they orbit the Sun in prograde orbits, but they are unlike planets in that they are small, very numerous, and have not "cleaned out" their neighborhood of the solar system.

Could you use a compass to find your way around Venus?

Venus has no magnetic field, so a compass would not be useful.

Do all the planets orbit the Sun in the same direction?

Yes. All the planets orbit the Sun in the same direction.

Which of the following characterize terrestrial planets?

composed primarily of rocky materials, high average densities, relatively small (size of Earth), have a definite surface

At least some of the largest satellites have characteristics that are dissimilar to characteristics of the terrestrial planets. Which of the following are among them?

composition includes much ice, low average densities

The largest satellites have some characteristics that are similar to characteristics of the terrestrial planets. Which of the following are among them?

have a definite surface, Similar sizes