THE MILKY WAY GALAXY BACKGROUND READING FOR MIDDLE AND HIGH SCHOOL SCIENCE
The Milky Way Galaxy The Milky Way is a huge collection of stars, dust and gas. It s called a spiral galaxy because if you could view it from the top, it would look like a spinning pinwheel. The Sun is located on one of the spiral arms, about 25,000 light years away from the center of the galaxy. Even if you could travel at the speed of light (186,000 miles per second), it would take you about 25,000 years to reach the middle of the Milky Way from Earth. Massive Black Massive Hole Black Hole The Milky Way gets its name from a Greek myth about the goddess Hera who sprayed milk across the sky. In other parts of the world, our galaxy goes by other names. In China it s called the Silver River, and in South Africa it s called the Backbone of Night.
Here is a real picture of what the Milky Way Galaxy looks like from Earth: If you could see our galaxy from the side, it would look like a huge, thin disk with a slight bump in the center. This flat shape is caused by the galaxy spinning around and around. Everything in our spinning galaxy would fly off into space if it weren t for the force of gravity.
Without a telescope, we can see about 6,000 stars from Earth. That may seem like a lot of stars, but it s actually only a small part of the whole. If you think of the entire galaxy as a giant pizza, all of the stars you can see from Earth fall within about one pepperoni on that pizza. In fact, for every star you can see, there are more than 20 million you cannot see. Most of the stars are too faint, too far away or blocked by clouds of cosmic dust. How do we know all of this? We have no real images of the Milky Way Galaxy because we have never sent a spacecraft outside of our galaxy. In place of a camera, scientists used large telescopes to determine the brightness of stars and the speed at which stars are moving. Based on these measurements, astronomers were able to figure out the size of the Milky Way Galaxy and map it out. An example of one of these special telescopes can be found at the Mount Wilson Observatory in California. Before scientists began using these large telescopes, it was thought that our sun was located at the center of the galaxy. This is another example of how ideas change over time as we get more and more evidence.
Other Interesting Facts Scientists have evidence that there is a massive black hole at the center the Milky Way Galaxy. A black hole is a region of space that has so much mass concentrated inside of it that there is no way for nearby objects to escape its gravitational pull. Not even light can escape the pull of a black hole. Black holes form when large stars run out of fuel and collapse on themselves. Our sun is just one star of an estimated 200 billion stars found within the Milky Way Galaxy! Some of these other stars also have planets rotating around them. Our sun is traveling around the center of the Milky Way Galaxy at a velocity of 136 miles per second! References http://www.amnh.org/ology/features/milkyway/ http://www.enchantedlearning.com/subjects/astronomy/solarsyste m/where.shtml http://www.fi.edu/learn/case-files/shapley/reading.html# http://www.astrophys-assist.com/educate/mmw/mmw.htm http://cosmology.berkeley.edu/education/bhfaq.html http://science.nationalgeographic.com/science/photos/galaxiesgallery/#/milky-way_1090_600x450.jpg http://www.atlasoftheuniverse.com/milkyway.html
Check out this incredible video to get a perspective of the Universe: http://www.amnh.org/news/2009/12/the-known-universe/
MILKY WAY GALAXY COMPREHENSION QUESTIONS 1. What is the Milky Way Galaxy made up of? 2. Draw a sketch of the Milky Way Galaxy and label the location of our Sun. 3. What is located at the center of our galaxy? 4. What force keeps everything in our galaxy from flying off into space? 5. What tools do scientists use to help them understand what our galaxy looks like?
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