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An Online Guide to Outer Space!

The next time it’s dark outside, take a look up at the sky. What can you see? Well, if it’s a clear night, you might say you see stars and the moon, which is true. Most people don’t realize just how many stars they can see with their naked eye, and even fewer realize that some of the “stars” they see are actually other planets! That’s right, you can see other planets right from your backyard! So the next time you are looking up at the sky, remember you are seeing more than stars and the moon, but whole other worlds. 

Stars

When you look up at the night sky and see all the stars up there, they might all look the same. Just big bright white lights up in the sky, thousands of them shining down on you. But did you know that these stars are all different sizes and colors? There are small stars called dwarfs and gigantic ones called giants, and they are different colors too, like red, yellow, and even blue! Here are some facts about the most common kinds of stars.

Yellow Dwarf

Why start this list with the yellow dwarf star? Because the sun is a yellow dwarf! Yellow dwarf stars are small and are in the middle of their lives as stars. The sun’s surface is almost 10,000 degrees Fahrenheit. Would you believe that even though the sun is considered a dwarf, it makes up over 99.8 percent of the mass of the solar system? And Jupiter makes up most of the other .2 percent! That means you can imagine everything in the solar system weighing only a hundred pounds, the sun would weigh 99.8 pounds! The Earth would weigh less than .1 pounds!

Red Giant

Let’s keep talking about the sun. Someday, billions and billions of years in the future, the sun will get much bigger. So big in fact that it might swallow up the Earth (don’t worry, this is going to happen a very, very long time from now). At this point, it will be late in its life as a star and will become a red giant, with a surface temperature below 9,000 degrees Fahrenheit, so even though the sun will be bigger, it will be a little cooler. In addition to being a little cooler, the sun will be a lot brighter, over 1,000 times as bright! There are a few red giants you can see with your naked eye from earth, with the most famous being Betelgeuse (which is pronounced like beetle juice). In order to find it, find the constellation Orion and look at the star that makes Orion’s shoulder. That’s a red giant!

White Dwarf

After the sun becomes a huge red giant, it will come to the end of its life as a star by becoming a white dwarf. Unlike when it was a yellow dwarf, the sun will, when it becomes a white dwarf, be just a little smaller than when it was a yellow dwarf, but a whole lot hotter, up to 200,000 degrees Fahrenheit. Eventually a white dwarf star will die, but even this takes billions of years. It takes so long, in fact, that a white dwarf created when the Universe first started is still radiating heat into the Universe.

  • How Are Stars Different? – No two stars are exactly the same. See how they are different from one another.

  • What Are Stars? – A whole site describing what stars are, how they form, and much more.

  • See the Stars – Depending on where you are, you may be only seeing a few hundred stars when you look up. Here’s how to see a few thousand!

  • Learn About the Stars – Facts and interesting information about stars and other parts of the Universe.

  • Ask an Astronomer – Answers to your questions from a real astronomer.

The Solar System

The Solar System is made up of much more than just the planets that orbit the sun. All the moons, dust, gas, comets, and asteroids are part of what we call the Solar System. In our case, the sun is the center of our Solar System, and everything that orbits around the sun is considered part of this Solar System. The amount of gravity a thing has is based on its mass, and since the sun makes up 99.8 percent of the mass of our Solar System, it has the most gravity and that’s why things orbit around it. The reason things don’t just plummet into the sun is that they are moving so fast, which makes them want to move away from the sun in a straight line. At a certain distance from the sun the gravity of the sun and the fast movement of the object (like an asteroid or comet) equal out and that object begins to orbit around the sun.

The Universe

Maybe the best way to look at the universe is by starting small. In our Solar System, objects orbit around the Sun. The Sun, though, also revolves around the center of our Milky Way galaxy, which is made up of 300 billion stars. The Milky Way galaxy is part of a huge number of galaxies called the Virgo Cluster, and there are millions of galaxy clusters around the world! In short, the Universe is huge! Bigger than we can even imagine, and it contains such wonders as black holes and between 100 and 200 billion galaxies!

Black Holes

It is possible that one day after the Sun dies, it will become a black hole. But how? Eventually a star will die and get smaller and smaller because it can’t support its own weight until it gets smaller than a single atom. Because it has gotten so much smaller but still weighs the same, the gravity is much stronger. Something as big as a star being reduced to the size of an atom would create such a strong gravitational pull that even light couldn’t make its way out. When that happens, the Sun will not be a star anymore, but a black hole.

Galaxies

The Milky Way is only one of billions of galaxies in the universe, and each galaxy carries within it somewhere between a few million and 400 billion stars. They come in three different varieties: Spiral, Elliptical, and Irregular. We are actually part of a spiral galaxy, the Milky Way. It is called a spiral because the stars, dust, and gas are gathered together in spiral arms that spread out from the center of the galaxy. An elliptical galaxy looks like stretched circles and are made up mostly of old stars. An irregular galaxy does not have a particular shape, and are some of the smallest galaxies in the Universe.