Question 1

The eastern elongation of Mercury's orbit:

Accepted Answer

The eastern elongation of Mercury's orbit depends on both the positions of Earth and Mercury in their orbits. When Mercury is at its closest point to the Sun and Earth is at its furthest point, Mercury's eastern elongation will be at its greatest. However, when Mercury is at its furthest point from the Sun and Earth is at its closest point, Mercury's eastern elongation will be at its smallest.

Question 2

Which of the following planetary configurations is IMPOSSIBLE for an inferior planet?

Accepted Answer

An inferior planet, such as Mercury or Venus, cannot be at opposition because it orbits closer to the Sun than Earth does, and opposition requires the planet to be on the opposite side of Earth from the Sun.

Question 3

When Saturn is at its farthest distance from Earth,it is at:

Accepted Answer

The answer of When Saturn is at its farthest distance...

Question 4

What is the angle between the line from Earth to Mercury and the line from Mercury to the Sun when Mercury is at greatest elongation?

Accepted Answer

When Mercury is at greatest elongation, it is at a right angle with respect to the Sun as seen from Earth. Therefore, the angle between the line from Earth to Mercury and the line from Mercury to the Sun is 90°.

Question 5

The synodic period of a planet is defined as the time between two successive:

Accepted Answer

The synodic period of a planet is the time it takes for the planet to return to the same position in the sky relative to the Sun, as observed from Earth, such as from one opposition to the next for outer planets or from one conjunction to the next for inner planets. This involves the Earth's position changing relative to the planet and the Sun, making option D correct.

Question 6

When Jupiter is at opposition,it will rise at:

Accepted Answer

When a planet is at opposition, it is opposite the sun in the sky, which means it will rise at sunset, be highest in the sky at midnight, and set at sunrise.

Question 7

When Saturn is closest to Earth,it is at:

Accepted Answer

When Saturn is closest to Earth, it is at opposition, which means it is on the opposite side of Earth from the Sun and appears fully illuminated in the night sky.

Question 8

At what position in its orbit does an inferior planet appear to be moving (for a day or two)more or less directly toward Earth? (See Figure 2-4 in Comins,Discovering the Essential Universe,6th ed.Draw a diagram if it will help.)

Accepted Answer

The answer of At what position in its orbit does...

Question 9

An inferior planet moves more or less directly toward Earth at greatest eastern elongation.What does this mean when you are watching the night-by-night motion of this planet against the background stars?

Accepted Answer

The answer of An inferior planet moves more or less...

Question 10

The time period between two successive passages of a planet through the position of opposition is:

Accepted Answer

The time period between two successive passages of a planet through the position of opposition is its synodic period. This is the time it takes for the planet to return to the same apparent position in the sky as viewed from Earth. It is slightly longer than the planet's sidereal period due to the motion of the Earth in its orbit around the Sun. For example, the synodic period of Mars is approximately 780 days, while its sidereal period is approximately 687 days.

Question 11

When a planet is seen at opposition,it is always at its:

Accepted Answer

When a planet is seen at opposition, it is directly opposite the Sun in the sky, which means that it is at its closest point to Earth.

Question 12

What is the angle between the line from Earth to Jupiter and the line from Earth to the Sun when Jupiter is at opposition?

Accepted Answer

When Jupiter is at opposition, it is directly opposite the Sun from Earth's perspective, meaning the angle between the line from Earth to Jupiter and the line from Earth to the Sun is 180°.

Question 13

Where and when would Venus be seen from Earth when it is at greatest elongation?

Accepted Answer

When Venus is at greatest elongation, it is at its maximum angular distance from the Sun as seen from Earth. If it is at greatest eastern elongation, it will be visible in the evening sky just after sunset in the west.

Question 14

The planet Venus can NEVER reach which planetary configuration when viewed from Earth?

Accepted Answer

The answer of The planet Venus can NEVER reach which...

Question 15

When Mars is at opposition,it is:

Accepted Answer

The answer of When Mars is at opposition,it is:
...

Question 16

The sidereal period of a planet is defined as the time between two successive:

Accepted Answer

The sidereal period of a planet is the time it takes to orbit the Sun and return to the same position against the background stars as seen from the Sun, not from Earth. This definition focuses on the planet's movement relative to distant stars, rather than its position as observed from Earth or its configuration in relation to the Sun and Earth.

Question 17

Where and when would Jupiter be seen from Earth when it is at opposition?

Accepted Answer

When Jupiter is at opposition, it is directly opposite the Sun from Earth's perspective, meaning it rises as the Sun sets and is visible all night, reaching its highest point in the sky at local midnight.

Question 18

In which part of the sky does Venus appear at sunset when it is at greatest elongation?

Accepted Answer

When Venus is at greatest elongation, it appears in the western part of the sky at sunset. This is because Venus is orbiting closer to the Sun than Earth, and when it is at greatest elongation, it has reached its maximum angular separation from the Sun as seen from Earth. As a result, it appears to be in the west at sunset, and can be seen for a short period of time after the Sun sets before it too dips below the horizon.

Question 19

Jupiter will be at which configuration when it is at the middle of its retrograde motion?

Accepted Answer

Jupiter, being a superior planet, undergoes retrograde motion when it appears to move backwards in the sky from our perspective on Earth. During retrograde motion, the planet appears to slow down, stop, and change direction relative to the background stars. The middle of retrograde motion occurs when the planet appears to stop moving backwards and transition back to direct motion. This occurs when the planet is at opposition, which is the point in its orbit where it is closest to Earth and directly opposite the Sun in the sky.

Question 20

Which of the following planetary configurations is NOT possible for the planet Mercury?

Accepted Answer

Opposition is not possible for Mercury as it is an inferior planet, meaning that it orbits closer to the Sun than Earth does. Therefore, it can never be in opposition, which is when a planet is on the opposite side of the Earth from the Sun. The other options, inferior conjunction, superior conjunction, and greatest elongation, are all possible configurations for Mercury.

Quiz 2: Gravitation and the Waltz of the Planets