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“So what’s in your solar system that’s so interesting?”

Even without a telescope, on a clear dark night you can see many amazing sights with your naked eye. Shooting stars streak across the night sky and the Big Dipper glows brightly. You can even spot planets, comets, and thousands of stars.

Just like everything else on Earth we are moving at an amazing speed through space. Earth is spinning on its axis at 1,000 miles per hour, and it is spinning around the Sun at 67,000 miles per hour. Even the whole solar system is moving. It is moving towards a star named Vega at 43,000 miles per hour, and it is spinning around the center of the Milky Way Galaxy at 540,000 miles per hour. Now that is fast! The reason we don’t feel this movement is because the ground, the atmosphere, and everything else is moving with us.

Our Moon

Atmosphere

If it weren’t for Earth’s atmosphere we might not be living. Earth’s atmosphere protects us from meteors because it burns them up when they enter the Earth’s atmosphere. It creates wind and rain that erodes our mountains and covers most of our lava beds with water and soil. The moon does not have an atmosphere so meteors can crash into it, leaving deep craters behind which can be as wide as the state of Connecticut. The weather does not erode the Moon’s huge mountains, and its dry lava beds are left undisturbed.

Revolution and Rotation

Just as the Earth revolves around the Sun, the moon revolves around the Earth. It takes 29.5 days for the moon to make one revolution around the Earth. The Earth takes 365 1/4 days to complete one revolution around the Sun. We have leap years every four years because if you add 1/4 of a day four times you will get one whole day, so then we just add the extra day to our year.

The moon rotates on an axis just like the Earth, and it takes 29.5 days for it to complete one rotation. The Earth takes 24 hours (one day) to complete one rotation.

It takes the moon the same amount of time to complete one rotation as it does to complete one revolution. It takes the Earth 365 1/4 days to complete one revolution and 24 hours to complete one rotation.

Moon Phases

Even though the moon does not produce its own light it is the brightest object in our night sky. We see the moon in the night sky because the Sun's light reflects off half of the moon's surface. The other half that faces away from the Sun is in complete darkness because there is no light to reflect off of it. As the moon revolves around the Earth we see different parts of its lighted side. The different shapes we see in the night sky are called phases.

Stars

Even though when you look at the night sky the stars seem to be about the same distance away, they really aren't. Some of the stars are hundreds of light-years (a light year is about 6 trillion miles) farther away than their neighbors. Since all of the stars are so far away from Earth, we can't make out the distances between them right away, not even when we look through a telescope.

Even though light can travel 700 million miles per hour, it takes a very long time for the light of any star in space to reach Earth. The Sun is 93 million miles away from Earth, so by the time the light reaches Earth it is 8 minutes old. The star Altair is 1,260 trillion miles away from Earth. It takes 210 years for the light from Altair to reach Earth. Can you imagine that? When the light gets here, we are seeing light that is 210 years old! The light we see today from a star Deneb left it 1,500 years ago. That was when Columbus sailed to the New World in 1492!

Planets

Early sky-watchers noticed that in the night sky some objects seemed to wander among the stars. They called these weird moving objects "planets," which means wanderers. Now, we know that planets are very different from stars. The reason they shine is because the light is reflected off of them from the Sun. They are much closer to Earth than the next-nearest star, too.

Milky Way Galaxy

When we look up at the night sky we can see part of the Milky Way galaxy stretching across the night sky even though we are part of the Milky Way. That is because we are located at one small part of the Milky Way Galaxy and from our position we can see the dense cloud of stars forming another piece of the Milky Way.

Meteors

When meteors enter the Earth’s atmosphere they burn up. During certain times of the year, the path of the Earth’s orbit around the Sun crashes into billions of tiny rocks that are usually leftovers from a comet or asteroid. When this happens we usually have what is called a meteor shower, when billions of the tiny rocks (meteors) burn up as they crash through the Earth’s atmosphere.

Comets

Spotting comets in the night sky is not something you see everyday. Some comets orbit the Sun so far away from Earth that we can never catch sight of them without using a telescope. Also some comets take a very long time to complete their orbit and are sometimes longer than the average human life. We are lucky enough for some comets to come close enough to the Earth for us to get a good look at them, like Halley’s Comet. As these comets approach the Sun, part of their frozen ice and gas surface evaporates, releasing long "tails" of dust and gas.

Asteroids

Although they are rare, killer asteroids are real possibilities and have actually hit Earth in the past.  Most asteroids are harmless, but some are so large they could do enough damage to end life on Earth.  Asteroids are thought to be remains of a planet that tried to form millions of years ago.

Galactic Slide Show

We found a great galactic slide show.  Click on the galaxy to the right to open a new window where you can view the slide show.  When you're finished, just close the window and you'll come right back here to learn lots more!

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Unless otherwise noted, all images courtesy of NASA. Permission for use at http://www.nasa.gov/gallery/photo/guideline.html.

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