After 75 years of research, radio, infrared and even x-ray telescopes have confirmed their existence, and found that the spiral cloud extends 100000 light-years (the diameter of the disk), with a thickness of 1000 light-years (the thickness of the disk). On this gorgeous disk, our tiny solar system lies on the inner edge of an arm, about 25000 light-years from the center.
Human beings determining the shape of the galaxy is like that a microorganism determines the shape of the earth. We can't get a good location to identify it, because this location must exist outside the galaxy. But looking at it from the outside of the galaxy gives you an overall picture of it.
In an area free from air pollution, the Milky way can be seen with the naked eye. When enjoying the beautiful scenery, the observer will notice that the twinkling stars are arranged in a narrow strip area through the darkness. There is a fuzzy bulge between this area, which is wider than the ribbon area on both sides. The appearance of such a compressed band of stars shows that we are looking at the side of a disk. The Milky way is a flat disk in which the bulge is the center of the galaxy.
Also, when we locate stars and measure their velocities, we find that this vector has a rotation component different from that of random motion. This is the characteristic of spiral galaxies. A star like the sun is formed when a huge dense cloud of hydrogen gas gathers under gravity. The remaining hydrogen dust or gas is dispersed by the new star flare. When the cloud interacts with light, it randomly scatters photons and creates light spots near the star. We can locate stars by searching for these spots, which are sun care landmarks. When astronomers located these points, they found that stars were focused on spiraling branches of light protruding from the center. We call these spiral branches "spiral arms" of spiral galaxies.
We study the properties of other spiral galaxies, such as the dust content, the order of stars and their speed, and compare them with our galaxy. Obviously, these findings are like the appearance of twins, with flat disks, gas friction, color and dust content shared by all spiral galaxies.
"Flower" in The Universe
So, some friends are curious, the universe does not exist in a void environment, why are nebulae? In fact, the nebula is not visible alone, and the universe is not without a minor gas, the nebula is through a universe of little gas and dust, slowly building an object that we now together to form a cloud lets see. - Nebula.
The trend of nebula is very large. The nebulae we see with our detectors are usually tens of light years in size, and as the name suggests, they are very low in density, like clouds on our planet, floating in space. The nebula is closely related to stars and, as described above, are clusters of dust and gas.
In fact, the nebula is not only beautiful, large nebulae are often accompanied by the birth of stars, once the size of the nebula, will continue to squeeze together, gradually forming a giant form. Increasing gravity will attract millions of millions of years or more of dust, gases and other substances, which we know are larger in size.
And the beautiful nebulae that we see, most of the planetary nebulae, are due to the fact that the center of the nebulae, or nearby, has glowing stars that reflect and refract light through the nebulae. As early as 1758, nebulae were discovered by a French astronomer, because of its unique characteristics, named nebulae, we also through the characteristics of nebulae glow, the nebulae into luminous gas clouds, dark nebulae, reflection nebulae and emission nebulae.
Stars Milky Way and colorful nebulae decorate the universe so beautifully and also enhance man's determination to explore the universe. When we look at the entire universe, the more mystery we discover, the more mysterious it feels to us, and the more awe we have. In the future, with the development of anthropology and technology, we may get more secrets!