How many planets are in the solar system?
There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto was reclassified as a dwarf planet in 2006.
The four inner planets, Mercury, Venus, Earth and Mars, are small and rocky. The four outer planets are much larger: Jupiter and Saturn are gas giants made mostly of hydrogen and helium, while Uranus and Neptune are called ice giants because they contain more water, ammonia and methane.
The International Astronomical Union defines a planet as a body that orbits the Sun, is massive enough to be round and has cleared its orbit of other objects. Pluto meets the first two rules but not the third, so in 2006 it became a dwarf planet.
A handy memory trick
To remember the order from the Sun, many people use the phrase My Very Educated Mother Just Served Us Nachos. Besides the eight planets, the solar system has at least five recognized dwarf planets, hundreds of moons and millions of asteroids and comets. Astronomers have also found thousands of planets orbiting other stars, called exoplanets.
Did You Know?
Jupiter is so big that more than 1,300 Earths could fit inside it. Mercury, the smallest planet, is only a little larger than our Moon.