Chapter 7: The Solar System Lesson 2: What Is the Solar System?

Why does Saturn take more time to orbit the Sun than Earth?

because it is so much further away from the Sun and so has a lot further to travel.

What are gases that make up the atmospheres of the outer planets?

hydrogen and helium

What are the main gases that make up Jupiter's atmosphere?

hydrogen and helium

Which planets have no moons?

Mercury Venus

Why do you think Mercury and Venus are so hot?

Mercury is the closest planet to the Sun; Venus has an atmosphere of thick clouds. These clouds are very hot .

How many fewer moons does Saturn have than Jupiter?

5

planet

A planet is a large round body of rocks, gases, or a combination of both that orbits a star, such as the Sun. The Sun, Earth, and Moon are parts of the solar system.

Why does Earth have a shorter year than Mars?

Because Mars spins on its axis in 24 hours and 36 minutes.

How are Earth and Mars alike and how are they different?

Differences: Mars has two small moons, while Earth has one moon. Mars has an atmosphere made up mostly of carbon dioxide and nitrogen. The air on Mars does not have enough oxygen. Similarities: Both are inner planets and have rocky surfaces.

Earth

Earth is the biggest of all inner planets. About 30 percent of its surface is covered by land and about 70 percent is covered by water. Earth's temperature, weather, and atmosphere, along with many other factors, are just right to keep people alive. There are currently almost seven billion people living on Earth. The Earth has one Moon.

What is the solar system?

It is made up of stars and anthor things in between.

Which planet has the greatest number of moons?

Jupiter has 67 moon

Jupiter

Jupiter is the largest planet in the solar system. Its atmosphere contains three layers of clouds made up of hydrogen and helium. Jupiter is stormy and has 67 known moons. It spins much faster than Earth. It completes two rotations in the time that Earth takes to complete one rotation.

Neptune

Like Uranus, Neptune has a blue color because its atmosphere is mainly made of methane gas. Neptune has a "Great Dark Spot." Scientists think that this spot is a hole in its atmosphere. Neptune has 14 known moons.

Why is Mars called the "Red Planet"?

Mars is the "Red Planet" because its soil contains iron oxide, which has a reddishbrown color

Mars

Mars is the "Red Planet" because its soil contains iron oxide, which has a reddishbrown color. It has an atmosphere made up mostly of carbon dioxide and nitrogen. The air on Mars does not have enough oxygen for living things. Mars spins on its axis in 24 hours and 36 minutes. It has two small moons.

Mercury

Mercury is the smallest and closest planet to the Sun, it is very hot and it has no moons. The surface of Mercury is dry and covered with craters. Craters are formed when rocks from space crash into the surface of a planet or moon. The temperature on Mercury's surface during the day can be 427 °C (800 °F). But at night, it can drop to under -180 °C (-290 °F).

Saturn

Saturn is the second largest planet in our solar system. In 1610, Galileo discovered that it had "lumps" on each side. In 1655, Christian Huygens discovered that Saturn actually has rings, not lumps. It is made mostly of hydrogen and helium. Saturn has 62 known moons.

orbit

The Sun's gravity pulls on the planets in the solar system. It makes each one of the planets move in nearly circular paths around the Sun called an orbit.

How are the inner and outer planets alike? How are they different?

The four inner planets have slower orbits, slower spin, no rings, and they are made of rock and metal. The four outer planets have faster orbits and spins, a composition of gases and liquids, numerous moons, and rings. The outer planets are made of hydrogen and helium, so they are called gas giants.

The Outer Planets

The four planets farthest from the Sun are called the outer planets. These planets are Jupiter, Saturn, Uranus, and Neptune. They are made up mostly of gases. These planets also have liquid inner layers and solid cores. Most of these planets are large. They have many moons and some have rings made of dust and rocks. These planets take a long time to move around the Sun.

What effect does the Sun's gravity have on the planets in the solar system?

The gravitational force of the Sun is so large that it keeps the planets in their orbits.

The Inner Planets

The inner planets, which are the closest to the sun, are Mercury, Venus, Earth, and Mars. All of these planets have rocky surfaces.

solar system

The solar system is made up of the Sun and other objects that revolve around the Sun in space. There are eight planets, including Earth.

Uranus

Uranus has rings like Saturn, although the rings are very thin. The atmosphere of Uranus is made of hydrogen, helium, and methane gas. Clouds of methane cover the whole atmosphere. This makes Uranus look bluish-green. It has 27 known moons.

Venus

Venus is about the same size as Earth. But it rotates on its axis in the opposite direction to that of Earth. On Venus, the Sun rises in the west and sets in the east. Venus has an atmosphere of thick clouds. These clouds are very hot and poisonous. It has no Moon.