Our solar system consists of the Sun and everything that orbits around the Sun. This includes the eight planets and their moons, dwarf planets, countless asteroids, comets, and other small, icy objects. However, even with all these things, most of the solar system is empty space.
The solar system itself is only a small part of a huge system of stars and other objects called the Milky Way galaxy. The solar system orbits around the center of the galaxy about once every 225 million years. The Milky Way galaxy is just one of billions of galaxies that make up the universe.
How the Solar System Was Formed
The solar system was formed about 4.7 billion years ago. It probably started as a loose cloud of gas and dust. Scientists think that gravity pulled parts of the cloud together into clumps. The largest clump was squeezed together so tightly that it got very hot. This clump eventually became the Sun. Over millions of years the other clumps became the planets. The Sun’s strong gravity eventually pulled the planets into their orbits.
The Sun and the Planets
At the center of our solar system is a star called the Sun. It is the largest object in the solar system. Its diameter, or distance through its center, is 1,392,000 kilometers. The sun is so large that it makes up more than 99% of the entire mass of the solar system. The Sun is a very hot ball of hydrogen and helium gasses. It has a temperature, at its core, of more than 15,600,000°C. The Sun gives out huge amounts of radiation. Living things on Earth depend on this energy, in the form of light and heat.
After the Sun, the largest objects in the solar system are the planets. In order from closest to the Sun, these planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Most of them orbit the Sun in paths shaped like circles and have at least one moon. However, different moons vary widely in size, temperature, and what they’re made of.
Scientists used to call Pluto the ninth planet. But in 2006, scientists decided that several objects in the solar system, including Pluto, should be called dwarf planets.
Adapted from “Solar System”, Britannica Kids, Encyclopædia Britannica. 23 January. 2022. kids.britannica.com/kids/article/solar-system/353789