The universe, the galaxy, and the solar system are distinct terms used to describe different scales and structures in the cosmos. Here are the differences between them:
Universe: The universe refers to the entirety of all matter, energy, space, and time. It encompasses everything that exists, including galaxies, stars, planets, and all other forms of matter and energy. The universe is vast and is believed to be expanding since the Big Bang, the theorized event that marked the beginning of the universe as we know it.
Galaxy: A galaxy is a massive system of stars, stellar remnants, interstellar gas, dust, and dark matter, all held together by gravitational forces. Galaxies come in various shapes and sizes, ranging from spiral galaxies (like the Milky Way) to elliptical galaxies and irregular galaxies. Each galaxy contains billions to trillions of stars, as well as other celestial objects like planets, asteroids, and comets. Galaxies are distributed throughout the universe.
Solar System: A solar system is a specific astronomical system that consists of a star (in our case, the Sun), its orbiting planets, dwarf planets, moons, asteroids, comets, and other smaller celestial objects. Our solar system, called the "Solar System," is located within the Milky Way galaxy. It contains eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), their moons, dwarf planets (such as Pluto), asteroids (rocky objects orbiting the Sun), comets (icy objects that follow elliptical orbits), and various other smaller objects.
In summary, the universe encompasses everything, including galaxies like the Milky Way, which, in turn, contain solar systems like ours. Each solar system consists of a star, planets, and other celestial bodies.