Galaxies are vast systems of stars, gas, dust, and dark matter bound together by gravity. They come in various shapes and sizes, ranging from dwarf galaxies with just a few billion stars to giants with a hundred trillion stars or more. The Milky Way, our home galaxy, is a barred spiral galaxy, meaning it has a central bar-shaped structure surrounded by spiral arms.The discovery of galaxies began in the early 20th century. Before that, astronomers believed the Milky Way was the entire universe. In 1920, Edwin Hubble made a groundbreaking discovery using the Hooker Telescope at the Mount Wilson Observatory. By observing the Andromeda Nebula (now known as the Andromeda Galaxy), Hubble identified Cepheid variable stars, which allowed him to calculate the distance to Andromeda. His findings showed that it was far beyond the Milky Way, proving that other galaxies existed.Hubble's work didn't stop there. He went on to classify galaxies into different types—spiral, elliptical, and irregular—based on their shapes. His research laid the foundation for modern astronomy, expanding our understanding of the universe's vastness. Today, with advanced telescopes like the Hubble Space Telescope and upcoming projects like the James Webb Space Telescope, we continue to explore galaxies, learning more about their formation, evolution, and the role they play in the cosmos.
