What Are the Planets in Order?
What are the planets in order from the Sun?
This guide gives the exact sequence, explains how the Solar System is organized, and highlights the differences between the rocky inner planets and the giant outer planets.
The order matters because it reflects how the Solar System formed, how the planets differ in size and composition, and why astronomers use specific definitions to classify them.
The planets in order from the Sun
The eight recognized planets, moving outward from the Sun, are:
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
This sequence is the standard used by NASA, the International Astronomical Union (IAU), and most astronomy textbooks.
A simple way to remember it is to separate the planets into two groups: the four inner rocky planets and the four outer giant planets.
Why the order starts with Mercury
Mercury is closest to the Sun, so it is the first planet in the lineup.
It is also the smallest planet in the Solar System and orbits the Sun faster than any other planet, completing one revolution in just 88 Earth days.
Because Mercury is so close to the Sun, it has extreme temperature swings and virtually no atmosphere to hold heat.
Its position helps explain why it is a small, dense, rocky world rather than a gas giant.
The inner planets: rocky worlds near the Sun
The inner planets are Mercury, Venus, Earth, and Mars.
They are often called terrestrial planets because they have solid, rocky surfaces and iron-rich cores.
- Mercury has a heavily cratered surface and almost no atmosphere.
- Venus is similar in size to Earth but has a dense carbon dioxide atmosphere and runaway greenhouse effect.
- Earth is the only known planet with liquid water on the surface and life.
- Mars is a cold, dusty planet with the largest volcano and canyon in the Solar System.
These planets formed from heavier materials that could survive closer to the young Sun, which is why they are smaller and denser than the outer planets.
The outer planets: giant worlds beyond the asteroid belt
Beyond Mars and the asteroid belt are the outer planets: Jupiter, Saturn, Uranus, and Neptune.
These worlds are much larger and contain different mixtures of gas, ice, and rock.
- Jupiter is the largest planet and has a massive magnetic field, dozens of moons, and the Great Red Spot.
- Saturn is known for its bright rings and low density.
- Uranus is an ice giant that rotates on its side.
- Neptune is the farthest planet and has some of the fastest winds in the Solar System.
Jupiter and Saturn are classified as gas giants because they are mostly hydrogen and helium.
Uranus and Neptune are called ice giants because they contain more water, ammonia, and methane in addition to hydrogen and helium.
Why Pluto is not in the planet order
Many people still ask where Pluto fits in the list of planets.
Pluto was once considered the ninth planet, but the IAU reclassified it as a dwarf planet in 2006.
Pluto does orbit the Sun and has a roughly spherical shape, but it has not cleared its orbital neighborhood of other objects.
That distinction is one of the key requirements for planethood under the modern definition.
So when people ask what are the planets in order, the correct answer today includes eight planets, not nine.
A quick memory trick for the planet order
If you need an easy way to remember the sequence, use the first letters:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
A classic mnemonic is: My Very Educated Mother Just Served Us Noodles.
It is popular because it matches the first letter of each planet in order.
How astronomers define a planet
The official definition of a planet in our Solar System comes from the IAU.
A planet must:
- Orbit the Sun
- Have enough mass for gravity to make it nearly round
- Clear its orbital neighborhood of other objects
This definition is why Earth, Mars, and the other major planets are included, while Pluto is not.
It also helps distinguish planets from dwarf planets, moons, asteroids, and comets.
Why the order of the planets matters in science
The planet order is more than a memorization exercise.
It reveals patterns in temperature, size, composition, and orbital behavior.
Inner planets are warmer and rockier, while outer planets are colder and richer in gases and ices.
It also helps explain planet formation.
In the early Solar System, lighter gases were more likely to be blown away near the Sun, while heavier materials and ices could accumulate farther out.
That is one reason Jupiter and Saturn became enormous.
Planet facts in order
- Mercury: closest to the Sun, no moons.
- Venus: hottest planet, thick atmosphere.
- Earth: liquid water and life.
- Mars: red color from iron oxide.
- Jupiter: largest planet, many moons.
- Saturn: iconic ring system.
- Uranus: tilted rotation axis.
- Neptune: farthest known planet, deep blue appearance.
If you are studying astronomy, teaching a child, or preparing for a quiz, this planet order is the standard reference to use.
It is the foundation for learning about orbits, planetary types, and the wider structure of the Solar System.