Galaxy
What is a Galaxy? Galaxy is a collection of stars held together by their mutual galaxy. A group of billions of stars and their planets, gas, and dust that extends over many thousands of light-years and forms a unit within the universe. Held together by gravitational forces. Most of the estimated 50 billion galaxies are shaped as spirals and ellipses, with the remainder being asymmetric. We are in Milky way galaxy and it is spiral galaxy. It has a bright central core with high density of stars and then a flattened disk surrounding it – like a spinning record. The Milky Way measures about 100,000 light-years across, and is thought to contain 200-400 billion stars. But the stars we can see are just a tiny fraction of the complete galaxy. It's also surrounded by a vast halo of dark matter. This material is invisible, and doesn't interact with regular matter or give off any kind of radiation that we can detect. But astronomers can measure its effects because it does exert a ...