Astronomy

Astronomy is a broad discipline covering all facets of astrophysics. In this section you can learn about the origins of the universe, black holes and other astronomical phenomena.

Topics to Explore

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What and where is the dark side of the moon?

The changing phases of the moon have given us an enduring curiosity about the dark side of the moon. But is there really a dark side of the moon? What would we see there?

Constellation Pictures

As every fledgling and seasoned astronomer knows, groups of stars that form some sort of arrangement are known as constellations. Peer at some of the most famous constellations that humans use to navigate, divine the future and tell stories.

Radio Telescope Image Gallery

Radio telescopes can give us some impressive insights into the universe. This collection of pictures highlights some of the images these telescopes have captured.

Nebula Image Gallery

Some of the most amazing star making regions in space are highlighted in this collection of nebula pictures. Check out some stunning pictures nebulae in this gallery.

Is there really water on Mars?

Until recently, most people assumed that if Mars had liquid water, it no longer did and hadn't for quite some time. But scientists have recently noticed some anomalies in photos of Mars that may suggest there is water. Could there be life, too?

What if I looked straight at an eclipse of the sun?

You've probably heard that staring at the sun is bad — even a few seconds can damage your eyes. But what if you looked at a solar eclipse?

How Asteroid Belts Work

Asteroid belts aren't quite the dense fields of gigantic spinning rocks that you may have seen in a "Star Wars" film, but they're still fascinating. In fact, the main asteroid belt may tell us how our entire solar system came into existence.

How the Moon Works

The moon is often the largest object in the sky outside of the sun. What is the moon made of, how did it form -- and why do people blame it for their strange behavior?

How the Milky Way Works

A look at the night sky at any time of year will reveal a faint band of light stretching across the sky -- our solar system's home, the Milky Way. How much do we really know about it?

How did a meteor make hundreds of people sick?

A ball of fire blazed through southern Peru and left a huge crater -- and then villagers started getting sick. Early reports said the groundwater boiled and the air filled with sulfur. What happened?

10 Memorable Meteor Crashes

Hundred of meteors fly across the sky every night, but only a few make it to Earth. Meteors are best known for the brilliant streaks of light they make as they burn up in the atmosphere. Learn about 10 memorable meteor crashes that left an impression.

How Solar Eclipses Work

A total solar eclipse is a rare event that can be an amazing thing to witness. Learn about solar eclipses and how to observe one safely.

Where did the moon come from?

We know it's not made of green cheese, but what are the origins of the moon? Learn astronomers' theories about where the moon came from.

Our Amazing Solar System

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 Explained

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.

Pluto Explained

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 Explained

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.

The Solar System Explained

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 Explained

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 Explained

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 Explained

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 Explained

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...

Earth Explained

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 Explained

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.

How do I build a telescope at home?

There are all kinds of telescopes, but you can make a simple one on your own. You'll need a few basic supplies and this step-by-step article. Get ready to star-gaze!


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