There are many different types of astronomical bodies in the universe, from huge stars to tiny particles of dust. In terms of size, the largest astronomical bodies are stars, while the smallest are subatomic particles. Here is a list of some common astronomical bodies from largest to smallest:
Stars: Stars are massive balls of gas that produce their own energy through nuclear fusion. Our Sun is an average-sized star and is about 1 million times the size of Earth. There are much larger stars in the universe though, with some reaching sizes up to 100 times that of our Sun.
Planets: Planets orbit around stars and range in size from small rocky worlds like Mercury and Mars, to giant gas giants like Jupiter and Saturn. Earth falls somewhere in between, making it a so-called “terrestrial†planet. In terms of size, planets can range from less than 1000 kilometers across (for example, Mercury) to over 150 thousand kilometers (for example Jupiter).
Moons: Moons orbit around planets and come in all shapes and sizes. Some moons are little more than chunks of rock or ice (such as our own Moon), while others have thick atmospheres and could even be considered mini-planets in their own right (such as Saturn’s moon Titan). The largest moon in our solar system is Jupiter’s Ganymede which has a diameter slightly larger than that of Mercury!
Asteroids & Comets: Asteroids are small rocky or metallic objects that orbit around the Sun; comets are similar but also have a “dirty snowball†composition including water ice and other frozen materials. Both asteroids and comets can vary greatly in size; for example Ceres –the largest asteroid– has a diameter close to 1000 kilometers while comet 67P/Churyumov-Gerasimenko –one of the most famous comets– only measures about 4 kilometers across at its widest point!
