There are billions of other galaxies in the Universe. All of this adds up to give us a picture of the Milky Way, even though we can't get outside to see the whole thing. Astronomers measure the amount of dust in the Milky Way and the dominant colors of the light we see, and they match those we find in other typical spiral galaxies. Robert Hurt, the Spitzer Science Center Robert Benjamin)Īdditional clues to the spiral nature of the Milky Way come from a variety of other properties. This artist's conception of the Milky Way's spiral structure is based on the measured distances of young, hot stars (shown in red) and ionized clouds of hydrogen gas (shown in blue). Since we can't get outside the Milky Way, we have to rely on markers of spiral arms like young, massive stars and ionized clouds. If we lived in an elliptical galaxy, we would see the stars of our galaxy spread out all around the sky, not in a single band. The concentration of stars in a band adds to the evidence that the Milky Way is a spiral galaxy. Several different telescopes, both on the ground and in space, have taken images of the disk of the Milky Way by taking a series of pictures in different directions a bit like taking a panoramic picture with your camera or phone. That band comes from seeing the disk of stars that forms the Milky Way from inside the disk, and tells us that our galaxy is basically flat. This band of stars can be seen with the naked eye in places with dark night skies. The first clue to the shape of the Milky Way comes from the bright band of stars that stretches across the sky (and, as mentioned above, is how the Milky Way got its name). Why do we think it is a barred spiral galaxy, then? There are several clues. We can only take pictures of the Milky Way from inside the galaxy, which means we don't have an image of the Milky Way as a whole. Read a NASA Blueshift blog post about how many stars there are in the Milky Way.It takes 250 million years for our Sun and the solar system to go all the way around the center of the Milky Way. Just as the Earth goes around the Sun, the Sun goes around the center of the Milky Way. Our Solar System is about 25,000 light years away from the center of our galaxy – we live in the suburbs of our galaxy. These stars form a large disk whose diameter is about 100,000 light years. Our best estimates tell us that the Milky Way is made up of approximately 100 billion stars. It is very difficult to count the number of stars in the Milky Way from our position inside the galaxy. Our galaxy is called the Milky Way because it appears as a milky band of light in the sky when you see it in a really dark area. All the stars we see in the night sky are in our own Milky Way Galaxy. The Milky Way is a large barred spiral galaxy. They come in a variety of shapes and sizes. A galaxy is a large group of stars, gas, and dust bound together by gravity. Our Sun (a star) and all the planets around it are part of a galaxy known as the Milky Way Galaxy. Here it is seen with several Atacama Large Millimeter/submillimeter Arra (ALMA) antenna. The band of the Milky Way galaxy can be seen at night in areas with dark skies.
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