The universe encompasses various systems, including: *solar systems, galaxies, and cosmological models*. A solar system consists of a star and the objects gravitationally bound to it, like planets and asteroids. Galaxies are massive collections of stars, gas, and dust. Cosmological models are mathematical representations of the universe, explaining its origin, characteristics, and evolution. Where Does the Solar System End? | Scientific American Here's a more detailed look at these systems: 1. Planetary Systems (including Solar Systems): Definition: A planetary system is a collection of gravitationally bound non-stellar bodies orbiting a star or star system. Examples: Our Solar System, which includes the Sun, planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), moons, asteroids, and comets. Exoplanetary Systems: These are planetary systems found outside of our Solar System, with astronomers discovering thousands of them. 2. Star Systems (including Binary Stars): Definition: A star system is a group of stars that are gravitationally bound to each other. Types: Binary stars (two stars), multiple-star systems (triple, quadruple, etc.). Significance: A significant portion of stars exist in binary or multiple-star systems. 3. Galaxies: Definition: A galaxy is a large collection of stars, gas, and dust, held together by gravity. Examples: Our galaxy, the Milky Way, contains billions of stars and their planetary systems. Structure: Galaxies can have various shapes and structures. 4. Cosmological Models: Definition: Mathematical representations of the universe, used to understand its origin, properties, and evolution. Significance: They help scientists understand the universe's expansion, the distribution of matter, and the role of dark matter and dark energy. 5. The Universe: Definition: The universe encompasses all of space, matter, energy, and time. Scale: The universe is vast, with galaxies clustered together in superclusters.