The Side of the Milky Way looks like a large disk with a slightly bulging center, the entire disk is about 100,000 light-years in diameter, and the solar system is located in the Milky Way Appreciation (20 photos) about 26,000 light-years from the center of the Milky Way. The bulging place is a dense area of stars, so it looks like a white expanse. The Milky Way is conduitous, with 4 spiral-shaped spiral arms extending evenly and symmetrically from the center of the Milky Way. The center of the Milky Way and the 4 spiral arms are all places where stars are densely packed
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(There are 4 larger spiral arms, but recent studies have shown that there are only two main spiral arms, and the other two are not fully developed) there are 946080000 billion kilometers. The thickest part of the middle is about 12,000 light-years.
The Sun sits on an arm called the Orion Arm, about 26,400 light-years from the center of the Milky Way, and rotates counterclockwise (it takes about 250 million years for the Sun to rotate around the galactic center). The discovery of the Milky Way has gone through a long process
After the invention of the telescope, Galileo first observed the Milky Way with a telescope and found that the Milky Way is composed of stars. Later, T. Wright, I. Kant, J.H. Lambert, and others believed that the Milky Way and all stars could converge into a vast star system.
In the late 18th century, F.W. Herschel began observations of star counts with a homemade reflecting telescope to determine the structure and size of the star system, asserting that the star system was flattened and that the Sun was not far from the center of the disk. After his death, his son J.F. Herschel succeeded his father and continued his in-depth research, extending the work of stellar counting to the southern heavens. In the early 20th century, astronomers referred to star systems with the Milky Way as a superficial phenomenon as the Milky Way. J.C. Kaptane applied the method of statistical parallax to determine the average distance of stars, combined with the star count, to obtain a model of the Milky Way.
In this model, the Sun is centered and the Milky Way is disk-shaped, with a diameter of 8 kilosecs and a thickness of 2 kilosecsecs. H. Shapley applied the weekly light relationship of Cepheids to determine the distance of globular clusters and study the structure and size of the Milky Way from the distribution of globular clusters.
The model he proposed was that the Milky Way was a lens-like star system with the Sun not in the center. Shapley concluded that the Milky Way is 80 kilosecscal in diameter and the Sun is 20 kilosseccicci from the galactic center. These values are too large because Shapley did not count interstellar extinction when calculating distances. In the 1920s, after the discovery of the rotation of the Milky Way, Shapley's model of the Milky Way was recognized. The Milky Way is a giant barred spiral galaxy (a type of spiral galaxy), Sb-type, with a total of 4 spiral arms.
Contains one to two hundred billion stars. The Milky Way as a whole rotates poorly, with the Sun spinning at a rate of about 220 km/s and the Sun orbiting the galactic center for about 250 million years. The Milky Way has a visual absolute magnitude of -20.5, and the total mass of the Milky Way is about 1 trillion times the mass of our Sun, roughly 10 times the mass of all stars in the Milky Way. This is strong evidence of the existence of dark matter in our Galaxy that extends far beyond the disks of bright stars.
Regarding the age of the Milky Way, the current dominant view is that the Milky Way was born shortly after the Big Bang in which the universe was born