The Solar System

In the Solar System Channel, you can explore the planets and celestial objects around our own sun. Learn about topics such as Mars, Jupiter and the Moon.


Some of the most interesting objects in our solar system are also the smallest or largest. In addition to the sun, planets, and moons, our solar system has a variety of small objects such as asteroids, comets, stars, meteors, and moons. These have affected what has happened on Earth in many ways.

Jupiter is the largest planet and is fifth from the sun. It is the third-brightest spot in our skies--after the sun and Venus. Jupiter is made up almost entirely of gas, which means it doesn't have a solid surface like Earth does.

The smallest and most-distant planet in our solar system is tiny, icy Pluto. It is even smaller than our moon, and wasn't discovered until 1930 — the only planet discovered in the twentieth century.

Mercury is the closest planet to the sun, and it is the second smallest. It is the fastest-moving planet, so it was named after the Roman god of speed. Like Earth, it is a terrestrial planet, meaning it has a solid surface that you could land on.

Our planet Earth is part of a solar system that consists of nine (and possibly ten) planets orbiting a giant, fiery star we call the sun. For thousands of years, astronomers studying the solar system have noticed that these planets march across the sky in a predictable way.

Neptune is the eighth planet from the sun, the fourth largest, and a gas planet. It is named after the Roman god of the sea. Neptune is four times the size of Earth, and its day lasts a little more than16 hours. Its year is about 165 Earth years. Neptune's orbit is a perfect circle. The last stop on spacecraft Voyager's epic trip through the solar system was the gas giant Neptune.

Uranus is the seventh planet from the sun, and is named for the ancient Greek deity of the Heavens, the earliest supreme god. It is the third largest planet in the solar system, and is three times as large as Earth.

Venus is the second planet from the sun, and is about the same size as Earth. It is a terrestrial planet, meaning it has a solid surface. But the harsh conditions on Venus make it very inhospitable. Two spacecraft, Pioneer Venus 1 and Magellan, were able to penetrate the thick atmosphere of this planet.

Saturn is the sixth planet from the sun and the second largest planet in the solar system. It is named for the Roman god of agriculture, one of the most important gods in the Roman world. Saturn is made mostly of hydrogen and helium, and its poles appear to be flattened because of its speedy rotation on its axis...

Saturn is the sixth planet from the sun and the second largest planet in the solar system. It is named for the Roman god of agriculture, one of the most important gods in the Roman world.

Mars, which is the fourth planet from the sun and the third smallest in size, got its name because of its rusty red color. People associated the planet's blood-red color with war, so they named it Mars, after the Roman god of war.

Since the 1960s, we've been captivated by our planetary neighbor. How different is the planet next door, and what have we learned about it so far, compliments of the Phoenix Mars Lander and other spacecraft?

The sun warms our planet every day, provides the light by which we see and is necessary for life on Earth. But what is it exactly, and what will happen when it burns itself out?

Why does the moon look so much bigger when it is near the horizon than when it is high up in the sky? This question has been pondered for hundreds if not thousands of years, and is commonly referred to as the moon illusion.

Where I live it is pretty common to see "shooting stars" -- streaks of light in the sky at night. How big is a shooting star? Do they land on earth or do they burn up? Do they land on the ground as meteorites?

The Chandler wobble is the change in the spin of the earth on its axis. Think of the wobble you see in a toy top when it first starts spinning or slows down. Its "poles" do not spin in a perfectly straight line.

If I was on the moon and the earth was black (no lights were on) and a flashlight was turned on facing the moon, would I see the light? If I couldn't, would there be any way to detect any residual matter that came from the light on Earth or does light die after a certain distance?

If "nature abhors a vacuum," then why doesn't the vacuum of space suck away all of the Earth's atmosphere?

Can the curvature of the Earth only be seen from outer space? If you didn't know that the Earth is a sphere, there are three common observations you could use to convince yourself that it is.