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Why do scientists believe that Titan is losing material from the top of its atmosphere into space?

Data from the Huygens probe suggest that at one point, Titan had an atmosphere five times as dense as it is today.

The astronomer Herschel's calculations of a celestial object he was studying in 1781 showed that its orbit was nearly circular. What was the significance of that?

Herschel realized he had discovered a new planet. It was the first discovery of a new planet in recorded history.

What do astronomers speculate about Jupiter's 55 outermost moons?

Astronomers speculate that these moons are captured asteroids; that is, that they used to orbit the Sun but veered close enough to Jupiter to be captured by its gravity.

Jupiter is how many times the mass of the Earth? Volume?

318 times, 1,400 times

How was Neptune's Great Dark Spot like Jupiter's Great Red Spot?

It was as big as earth, essentially a storm system, and had extremely high wind speeds.

What's unique about Uranus's rotation?

Its axis is tilted 90 degrees to its orbital plane.

What are the four furthest planets from the sun categorized as?

Jovian planets

What is the biggest planet in the solar system?

Jupiter

What did most astronomers think when it became clear that Uranus wasn't behaving quite the way Newton's laws predicted?

Most astronomers thought another planet was somehow disturbing Uranus's orbit.

Jupiter is somewhat ___________.

Oblate

What did Galileo find out about Jupiter's atmosphere?

The Galileo spacecraft found Jupiter's atmosphere to be about 90 percent hydrogen and 10 percent helium, with small amounts of methane, ammonia, and water vapor. Galileo also found small amounts of certain heavier elements

Saturn's atmosphere is like those of which two other bodies in the Solar System? How so?

Saturn's atmosphere is like that of Jupiter and the Sun: about 96 percent hydrogen, 3 percent helium, and 1 percent heavier materials.

Why does Saturn appear so different from Earth at different points in its orbit?

Saturn's rings are in the plane of its equator, and the planet tilts 27 degrees with respect to its orbital plane. So as both Earth and Saturn orbit the Sun, earthlings will sometimes see the edge of Saturn's rings, and at other points during Saturn's orbit they will observe the rings' "top" and "underside."

What is Jupiter's differential rotation and what does it indicate?

The phenomenon of different parts of a planet having different periods of rotation is known as differential rotation. It indicates that Jupiter's visible surface isn't solid.

What makes up Saturn's rings?

The rings are made up of chunks of water ice and smaller bits of rock and organic matter.

What feature of Uranus did scientists discover in 1977 while measuring the planet? What are the key characteristics of this feature?

They were able to make the first reliable determination of its diameter. They used occupation, which measures how fast Uranus travels and how far it is from the sun.

What is unusual about the orbit of Triton? Of Nereid?

Triton revolves clockwise around the planet. Nereid has the most eccentric orbit of any moon.