Question 1

When Galileo first discovered the large moons of Jupiter in 1610, he called them:

Accepted Answer

Galileo named the moons he discovered the Medicean stars in honor of his patron, Cosimo II de' Medici and the Medici family.

Question 2

What can we say about the observations of the four large satellites of Jupiter before Galileo's telescopic observation of 1610?

Accepted Answer

The four large satellites of Jupiter (Io, Europa, Ganymede, and Callisto) have magnitudes ranging from 4.6 to 5.6, which is technically visible to the naked eye. However, their proximity to bright Jupiter would have made it difficult to resolve them individually without a telescope, so it is unlikely they were observed before Galileo's telescopic observations in 1610. Therefore, choice B is the best answer.

Question 3

The four major satellites of Jupiter are collectively named after which early astronomer?

Accepted Answer

The four major satellites of Jupiter (Io, Europa, Ganymede, and Callisto) are collectively named the Galilean moons after Galileo Galilei, who discovered them in 1610 using an early telescope.

Question 4

How many satellites of Jupiter were seen by Galileo?

Accepted Answer

Galileo saw four satellites of Jupiter: Io, Europa, Ganymede, and Callisto.

Question 5

It has been known that Jupiter has satellites since:

Accepted Answer

Jupiter's four largest moons, known as the Galilean moons, were first discovered by Galileo Galilei in 1610 using his telescope. Therefore, the correct choice is C.

Question 6

How many large, spherical satellites are in orbit around Jupiter?

Accepted Answer

Jupiter has four large, spherical satellites known as the Galilean moons: Io, Europa, Ganymede, and Callisto.

Question 7

Which spacecraft reached Jupiter most recently?

Accepted Answer

Juno is the most recent spacecraft to reach Jupiter, having entered orbit in July 2016.

Question 8

Which of the following motions is seen to be characteristic of the four Galilean satellites of Jupiter?

Accepted Answer

The Galilean satellites of Jupiter are known for their synchronous rotation, meaning that they keep the same face towards the planet at all times. This is a characteristic motion that sets them apart from other moons in the solar system.

Question 9

Because of mutual gravitational forces between the satellites and the planet, the orbital periods of the three inner Galilean satellites of Jupiter are in the ratio:

Accepted Answer

The orbital period is proportional to the 3/2 power of the semi-major axis, so the ratio of the two should be (a/b)^(3/2)=2, and (b/c)^(3/2)=2. Solving these equations, we get a:b:c=1:2:4, giving us choice D as the correct answer.

Question 10

If the orbital period of Io, the innermost Galilean satellite of Jupiter, is 1.77 days, what is the rotation period around its own axis?

Accepted Answer

Io is in synchronous rotation with Jupiter, meaning that it rotates on its own axis at the same rate that it orbits around Jupiter. Therefore, its rotation period is the same as its orbital period, which is 1.77 days.

Question 11

What is the relationship between the orbital periods of the four Galilean satellites of Jupiter?

Accepted Answer

The correct relationship between the orbital periods of Io, Europa, and Ganymede is a near 1:2:4 resonance, known as a Laplace resonance. Callisto does not participate in this resonance, thus there is no simple integer relationship between Callisto and Ganymede.

Question 12

Three of the Galilean satellites of Jupiter have orbital periods that are in the ratio 1:2:4. The Galilean satellite that does NOT have such a relationship is:

Accepted Answer

Callisto does not fit into the 1:2:4 orbital resonance pattern shared by Io, Europa, and Ganymede. This resonance is known as a Laplace resonance.

Question 13

Io, Europa, and Ganymede have orbital periods in the ratio 1:2:4. At some time all three satellites are lined up on the same side of Jupiter as seen from Earth. After Europa goes once around Jupiter:

Accepted Answer

Since Ganymede's orbital period is twice that of Europa, Europa and Ganymede will always be on opposite sides of Jupiter. When Europa completes one orbit, it will be on the same side of Jupiter as Io, but Ganymede will be on the opposite side. Therefore, all three satellites will be lined up, but Ganymede will be on the opposite side of Jupiter as seen from Earth.

Question 14

If the orbital period of Jupiter's satellite Ganymede is 7.15 days, what would be the view from a point on its surface at the equator?

Accepted Answer

From a point on Ganymede's equator, Jupiter would always be at the same point in the sky (assuming it is visible), but the Sun would appear to rise and set with a period of approximately 7.15 days due to Ganymede's orbital period.

Question 15

In terms of the relationship between the periods P and semimajor axes a of their orbits around Jupiter, how do the satellites of Jupiter behave?

Accepted Answer

The satellites of Jupiter follow the Keplerian relationship P² = ka³, in which k is a constant that is different from the constant governing planetary motion around the Sun, because they orbit Jupiter and not the Sun. The constant k depends on the mass of Jupiter and the semimajor axis of the satellite's orbit.

Question 16

In describing the observations of the movements of the satellites of Jupiter, what is the difference between an occultation and an eclipse?

Accepted Answer

An occultation occurs when a satellite of Jupiter passes behind the planet and disappears from view, whereas an eclipse occurs when a satellite passes into the planet's shadow and may partially or completely disappear from view. Therefore, option D is the correct answer.

Question 17

It is rare to see Jupiter's Galilean satellites occult one another. Why is such an event seen only rarely?

Accepted Answer

The orbits of Jupiter's Galilean satellites are almost in the same plane, but Earth only occasionally aligns with this plane, making occultations rare events observable from Earth.

Question 18

Suppose you have calculated the speed of Ganymede in its orbit from Kepler's laws. You time the interval between when Ganymede first begins to disappear into Jupiter's shadow and when it is totally occulted by Jupiter. What can you calculate from this information?

Accepted Answer

The time it takes for Ganymede to be totally occulted by Jupiter, combined with its orbital speed, can be used to calculate the radius of Ganymede.

Question 19

Of the spacecraft that have visited Jupiter, which was placed in orbit around the planet?

Accepted Answer

Galileo was the only spacecraft that was placed in orbit around Jupiter, allowing it to make multiple close observations and measurements of the planet and its moons. Pioneer and Voyager provided flyby views as they traveled to other planets.

Question 20

Which of the following properly lists the planets and satellites of planets in order of decreasing density?

Accepted Answer

Mercury, being a planet, has a higher density than the moons listed due to its large metallic core. Among the moons, Io, being the most geologically active due to tidal heating from Jupiter, has a higher density than the Moon and Europa, which are less geologically active. Europa, being primarily composed of water ice over a possible subsurface ocean, has the lowest density among the listed bodies.

Quiz 13: Jupiter and Saturns Satellites of Fire and Ice