Getting to Know: Planets in Our Solar System The other night you and your mother decided to go stargazing together. You found a good spot and set up blankets to sit on. You sat down and looked at all the stars.

“What is that really bright star?” you asked. Your mother looked at the object you were pointing to.

“That’s Venus,” she said. “It’s a planet in our solar system. It looks very bright because it’s much closer to us than the stars. Some nights you can also see Mars.”You wrapped another blanket around yourself and settled in to watch.

Which objects make up our solar system? Our solar system is made up of the Sun and all of the objects that orbit it. These include the eight planets and their moons as well as asteroids and comets.

The night sky is full of stars, planets, and other objects.

What are the planets? Planets are large bodies in space that orbit stars. In our solar system, Earth is one of eight planets that orbit the Sun. The other planets are Mercury, Venus, Mars, Jupiter, Saturn, Neptune, and Uranus.

If you are standing on Earth looking at the night sky, the planets will look like stars. However, the planets will appear to change positions in the sky against the background of other stars.

What are the characteristics of planets? All of the planets in our solar system are roughly spherical in shape. They also move in orbits that are nearly circular.

Most of the planets have moons. The moons orbit the planets in the same way that the planets orbit the Sun. Mercury and Venus are the only planets that do not have a moon.

Misconception 1: I thought that all the planets have solid surfaces. Is that true?

The outer planets are mostly made of gas and debris. They are not rocky and solid like the inner planets. If you tried to stand on one of the outer planets, you would sink straight through!

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What are the inner and outer planets? The inner and outer planets are very different. The inner planets are Mercury, Venus, Earth, and Mars. They are closer to the Sun than the outer planets. These planets are small and rocky and are mostly solid.

The outer planets are Jupiter, Saturn, Neptune, and Uranus. They are much further from the Sun. These planets are much larger and are mostly made of gas.

Misconception 2: I saw a drawing in which the planets were arranged in a straight line from the Sun. Is this how they look in real life?

Diagrams often show planets in a straight line because it is a simple way to show all the planets. In real life, the planets are not in a straight line. For one thing they have different orbital paths and speeds. It would not be possible for them to line up perfectly. Even if they did, each planetary orbit is tilted slightly. The “line” they would make would be very crooked.

Besides planets, what other objects are found in the solar system?

A belt of large rocks orbits the Sun between the inner and outer planets. These rocks are known as asteroids. This area is called the asteroid belt.

A similar area exists beyond the outer planets. This is called the Kuiper belt. The Kuiper belt includes Pluto and millions of other rocky objects that orbit the Sun.

In this model of the solar system you can see the asteroid belt between the inner and outer planets.

Comets are also found in the solar system. Comets are made of ice, rock, and gas. When they come near the Sun, some of the ice melts. This causes them to leave long trails of ice and gas. This is where they get their famous “tails.”

Concept: Planets in Our Solar System Getting to Know www.discoveryeducation.com

2 © Discovery Education. All rights reserved.

Discovery Education is a subsidiary of Discovery Communications, LLC.