The Solar System is a collection of planets, moons, comets and asteroids all traveling around a central star, the Sun.
Our sun is 4.6 billion years old and its gravity holds all the objects in orbit. This solar system is diverse and complex.
What is a planet?
A planet is a body that orbits a star. They are formed from clumps of rock and debris that collide and stick together as they orbit the star.
In 2006 the International Astronomical Union (IAU) adopted a definition of planethood that included two main criteria, including that they must be in orbit around the Sun and that they must be round. However, this definition did not clearly state what it meant to “clear the neighborhood” around their orbits.
What is a moon?
A moon is a natural satellite that orbits a planet or dwarf planet. There are more than 140 known moons in our Solar System.
The largest known moon is Ganymede on Jupiter. Its diameter is nearly twice as large as either Mercury or Pluto.
Saturn has two ocean moons – Enceladus and Titan, which have seas of liquid ethane and methane. They are the only moons with surface oceans in our Solar System.
What is a comet?
A comet is an icy object that forms out in the outer parts of our solar system. These objects are left over from the formation of our sun 4.6 billion years ago, and many of them exist in a wide disk beyond Neptune called the Kuiper belt.
As comets near the Sun they heat up, causing their frozen ice to change into gas. This gas is composed of water vapor, carbon monoxide and other trace substances. The escaping gas is then swept into the distinctive tail of a comet.
What is a nebula?
A nebula is a cloud of gas, dust, plasma and hydrogen that can be seen in space. Nebulae are often considered “stellar nurseries,” the location where stars form and grow.
Many nebulae are dark clouds, formed when gases and particles in the interstellar medium are pulled together by gravity. The resulting density causes them to collapse.
These types of nebula are typically called emission nebulae. They emit ultraviolet light because they have ionized gas in their cloud.
What is a asteroid?
Asteroids are the leftover chunks of rock and metal that formed our solar system billions of years ago. When lumps of rock and metal bumped into each other, they stuck together to form bigger lumps that had stronger gravity.
They then moved around the Sun in orbits shaped by gravity. Most asteroids orbit between Mars and Jupiter in a ring called the asteroid belt.
Asteroids vary in size from hundreds of miles to a few feet across. They are usually lumpy and shapeless, but some of them are round.
What is a meteorite?
A meteorite is a piece of rock that has come from space and hit Earth. They are very rare and usually don’t make it to the ground, but people often find rocks or pieces of metal that they think might be meteorites.
Meteorites are classified according to their petrology (how they formed) and origins. The majority of meteorites are stony type, such as chondrites and achondrites. Others are metallic, such as iron meteorites or stony-iron meteorites. Some come from the Moon or Mars.
What is a meteor?
Meteors are streaks of light in the sky, typically caused by a space rock that enters Earth’s atmosphere. These meteors are usually visible during nighttime, but especially bright ones can be seen during daylight hours.
Meteors are primarily composed of small bits of rocky or metal space junk that travel around in the solar system. Some of these particles are leftover from comets, while others are fragments from planets or asteroids.