What are the Milky Way and Extragalactic Galaxies like?

The Milky Way is the galaxy to which the earth and the sun belong. It is named because the bright band whose main part is projected on the celestial sphere is called the Milky Way in China. There are about 200 billion stars in the Milky Way. The Milky Way looks like a big disk with a slightly protruding center. The diameter of the whole disk is about 654.38+ million light years, and the sun is located 23,000 light years away from the center of the Milky Way. What bulges is a silver heart, which is a dense area of perseverance, so I look at a vast expanse of whiteness. The Milky Way looks like a huge whirlpool from the top, which is composed of four spiral arms. The solar system is located in one of the spiral arms (Orion arm) and rotates counterclockwise (it takes 250 million years for the sun to rotate around the center of the Milky Way).

Extragalactic galaxies, referred to as galaxies for short, are celestial systems located outside the Milky Way and composed of billions to hundreds of billions of stars, nebulae and interstellar matter. At present, about 654.38+billion extragalactic galaxies have been discovered. The Milky Way is just an ordinary galaxy. It is estimated that there are more than 1000 billion galaxies outside the river, which are like islands dotted in the vast ocean, so they are also called "cosmic islands".