About Planets
Our solar system has eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There are five officially recognized dwarf planets in our solar system: Ceres, Pluto, Haumea, Makemake, and Eris.
Planets
Dwarf Planets
Introduction
What is a planet? The word traces back to the ancient Greek word planētēs, which means “wanderer.” A more modern definition can be found in the Merriam-Webster dictionary, which defines a planet as a large body that revolves around the Sun in our solar system.
In 2006, the International Astronomical Union (IAU)—a group of astronomers that names celestial objects—adopted a definition of a planet for our solar system. This new definition caused Pluto's famous “demotion” to a dwarf planet, and it reduced the number of planets in our solar system from nine to eight. Currently, the IAU recognizes five dwarf planets: Ceres, Pluto, Haumea, Makemake, and Eris.
Beyond our solar system, scientists have found thousands of planets, called exoplanets. Most orbit other stars, while some—called rogue planets—just float on their own. Research indicates there are more planets than stars in our galaxy, the Milky Way.
This page gives you a quick guide to the planets and dwarf planets in our solar system and introduces our Exoplanets section where you discover even more worlds.
Inner Planets
The first four planets from the Sun are Mercury, Venus, Earth, and Mars. These inner planets also are known as terrestrial planets because they have solid surfaces.
Mercury Facts
Mercury is the planet nearest to the Sun, and the smallest planet in our solar system.
Earth Facts
Earth – our home planet – is the third planet from the Sun, and the fifth largest planet.
Outer Planets
The giant planets in the outer solar system don't have hard surfaces. Instead, they have swirling gases above a core. Jupiter and Saturn are gas giants. Uranus and Neptune are ice giants.
Jupiter Facts
Jupiter is the fifth planet from the Sun, and the largest planet in our solar system.
Saturn Facts
Saturn is the sixth planet from the Sun, the second largest planet in our solar system.
Uranus Facts
Uranus is the seventh planet from the Sun, and the third largest planet in our solar system.
Neptune Facts
Neptune is the eighth and most distant planet in our solar system. It's the fourth largest planet.
Dwarf Planets
The confirmed dwarf planets include longtime favorite Pluto, along with lesser known worlds Ceres, Makemake, Haumea, and Eris.
Ceres Facts
Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter, and it's the only dwarf planet in the inner solar system.
Pluto Facts
Pluto was long considered our solar system's ninth planet. It was reclassified as a dwarf planet in 2006 by the International Astronomical Union.
Haumea Facts
Haumea was nicknamed Santa by one discovery team. It is oval-shaped, and is one of the fastest rotating large objects in our solar system.
Makemake Facts
Makemake is slightly smaller than Pluto, and is the second-brightest object in the Kuiper Belt, while Pluto is the brightest.
Eris Facts
The discovery of Eris led to the decision to clarify the definition of a planet. That new definition bumped Pluto to dwarf planet status.
Planet Sizes and Locations in Our Solar System
Our solar system has eight planets, and five officially recognized dwarf planets. Which planet is biggest? Which is smallest? What…
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Is There Another Planet in our Solar System?
It's an intriguing idea that might explain some current mysteries, but direct evidence of another planet has yet to be found.
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Temperatures Across Our Solar System
Let’s look at the mean temperature of the Sun, and the planets in our solar system.
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Exoplanets
An exoplanet is any planet beyond our solar system. Most of them orbit other stars, but some free-floating exoplanets, called rogue planets, are untethered to any star. We’ve confirmed more than 6,000 exoplanets, out of the billions that we believe exist.
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