Jeremy taught elementary school for 18 years in in the United States and in Switzerland. He has a Masters in Education from Rollins College in Winter Park, Florida. He's taught grades 2, 3, 4, 5 and 8. His strength is in educational content writing and technology in the classroom
What is a Galaxy?
A galaxy is a large cluster of stars, planets, star clusters, gas and dust all gathered and held together by gravity. Amazingly, scientists estimate that there could be over 100 billion galaxies in the observable universe. That means if you tried to count them all, you couldn't do it even if you spent your entire life counting! Galaxies come in different shapes and sizes. Some are small, called dwarf galaxies, and contain 10 million stars, while others are massive, holding more than 100 trillion stars. They can have different shapes, too. They can be spiral, like the Milky Way, elliptical, lenticular (disc shaped) or irregular.
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The Milky Way
The Milky Way is a large galaxy that has a spiral shape. Its actual shape is called a barred spiral galaxy. There is a bar in the center and many arms that extend out from the center. Our own solar system lies in one of the arms of the Milky Way, making a complete rotation in around 200 million years. The center of the Milky Way cannot be seen due to a heavy amount of gases, however, scientists believe that the center is a super massive black hole. The black hole may be the source of gravity that holds the galaxy together.
The Milky Way is part of a cluster of galaxies near each other that is called the Local Group. The Local Group also includes another large galaxy called the Andromeda Galaxy. The Milky Way is about 13 billion years old and contains over 200 billion stars. To imagine how big the entire galaxy is, you'd have to imagine that light would take 100 thousand years to pass from one side to another.
Cool Facts about the Milky Way
Alright, before we wrap up, let's take a closer look at some cool facts about the Milky Way. Some of them might surprise you!
- The Milky Way was named because it has a milky look at night when you look up at the sky.
- Because we are part of the Milky Way, we don't have any pictures of what it really looks like. We can only use other similar galaxy images to make a guess.
- Based on current observations, the Milky Way will collide with the neighboring galaxy of Andromeda in less than 4 billion years.
- It wasn't until the year 1924 that we knew that other galaxies besides the Milky Way even existed.
- The oldest star in the Milky Way is over 13 billion years old, which many scientists believe is almost as old as the universe itself.
- Since our solar system is under 5 billion years old, it has only rotated with the Milky Way about 20 times.
Okay, let's take one last moment to review the important information we learned in this lesson.
We first learned that galaxies are large clusters of stars, planets, star clusters, gas and dust all gathered and held together by gravity. The Milky Way is a large galaxy in the Local Group of galaxies that is home to our solar system. It is a barred spiral galaxy that contains more than 200 billion stars and is 100,000 light years across. The center is believed to contain a black hole that is responsible for the gravity that holds the Milky Way together.
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Milky Way Facts: Lesson for Kids
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