Galaxies
Presentation
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Science
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6th Grade
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Practice Problem
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Easy
Standards-aligned
Michael McCrory
Used 111+ times
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18 Slides • 4 Questions
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Galaxies
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This fuzzy band of light in the night skys is the Milky Way, our Galaxy
Galileo discovered that the light in it is actually stars.
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The Shapes of Galaxies
Galaxies are huge, yet they are very unique, and there are billions of them in the universe. Galaxies are different ages, sizes, and distances from Earth. Astronomers classify galaxies by shape: spiral, elliptical, and irregular.
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Spiral Galaxies
get their name for their arms of gas, dust, and stars that spiral out from a densely packed cluster of stars in the center. Spiral galaxies typically have a mix of stars, some young and some old.
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The Milky Way
The Milky Way is a special type of spiral galaxy, called a barred-spiral galaxy. Barred-spiral galaxies have a thick bar of stars and gas passing through their centers. From Earth, the fuzzy white band of the Milky Way doesn’t look like a spiral; it looks like a stripe. That is because you are looking at the Milky Way sideways, from inside one of its spiral arms.
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Elliptical Galaxies
An elliptical galaxy has a shape like a stretched circle, or oval. Elliptical galaxies usually include only old stars. This is because they contain little gas or dust.
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Irregular Galaxies
As their name suggests, irregular galaxies have no distinct or orderly shape. Many new stars are born in irregular galaxies. This is because these galaxies contain far more gas and dust than elliptical or spiral galaxies.
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Galaxy Clusters
A group of close together galaxies is known as a galaxy cluster.
There are many of these clusters throughout space.
They seem to occur randomly, sometimes there are lots of clusters in one area, then almost none in others.
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Spinning Galaxies
Since the big bang, galaxies have been moving away from each other. Galaxies move in other ways, too. For example, spiral galaxies spin fast in the center, while their arms spin slower. Many scientists think that several, or perhaps most, galaxies rotate around the enormous gravitational pull of a massive black hole at their center.
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Black Hole
a region in space where it is theorized that no mass or light can escape
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The speed of a galaxy
The sun circles the center of the Milky Way at a speed of about a half a million miles an hour. Even at that rate, it takes the sun more than 200 million years to make one complete orbit Opens in modal popup windowaround the center of the galaxy!
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Holding it all together
How do each of these gigantic galaxies stay clumped together? What keeps everything in the universe from spinning out into space? The law of universal gravitation holds each galaxy together. This same force causes you to return to the ground after you jump into the air. In the next lesson, you will learn more about the force of gravity
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