In terms of scale, the universe is significantly larger than both galaxies and solar systems. Here's a breakdown of each:
Universe: The universe encompasses all matter, energy, space, and time. It is vast and consists of countless galaxies, galaxy clusters, superclusters, and other cosmic structures. It is estimated to be around 93 billion light-years in diameter, although it could potentially be much larger.
Galaxy: A galaxy is a large system of stars, gas, dust, and other celestial objects bound together by gravity. Our own galaxy is called the Milky Way. Galaxies can vary in size, but they typically contain hundreds of billions to trillions of stars, along with various stellar systems, such as planets, asteroids, and comets. The Milky Way is approximately 100,000 light-years in diameter.
Solar System: A solar system is a smaller component within a galaxy. It consists of a central star (in our case, the Sun) and various celestial bodies, including planets, moons, asteroids, and comets, which orbit the star. Our solar system contains eight planets, including Earth, and their respective moons, as well as numerous smaller objects. The size of the solar system is defined by the outermost known objects, such as the dwarf planet Pluto, which is about 7.5 billion kilometers away from the Sun.
Therefore, the hierarchy, from smallest to largest, is solar system < galaxy < universe.