Solar System

Venus rotates in the opposite direction from all other planets in the solar system.

Venus is the brightest planet in the Earth's sky. Its yellow clouds are composed of sulfuric acid and reflect the sun's light.

The solar system is composed of eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The commonly accepted ninth planet, Pluto, was downgraded to a dwarf planet in 2006.

The outer planets of Jupiter, Saturn, Uranus and Neptune are primarily composed of hydrogen, helium, and other gases.

The moons of Uranus are named for fairies such as Titania, Oberon, and Ariel.




The inner planets of Mercury, Venus, Earth, and Mars are terrestrial and composed of metal and rock.

The Hubble Telescope is a multi-billion dollar device set into orbit that helps astronomers and scientists discover more information about the solar system and beyond.

The Earth has one satellite: the moon.

The downgrade of Pluto to a dwarf planet confused generations of school children who grew up memorizing the solar system's nine planets. Since that downgrade, scientists have identified more than 13 planetary-like bodies within the solar system.

Saturn is the second largest planet in the solar system. Its rings are composed of a moon's remnants.

Pluto, the dwarf planet, has three known moons -- Charon, Hydra, and Styx.

Pluto and Neptune trade places in their orbits to be closer to the sun.

Olympus Mons on Mars is the largest volcano in the solar system.

Neptune's moons are named for beings associated with the God of the Seas, including Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton, Nereid, Halimede, Sao, Laomedeia, Psamathe, and Neso.

Neptune is on the outer rim of the solar system and was discovered in 1846.

Mercury and Venus have no satellites.

Mars has two moons: Phobos and Deimos. They are believed to be captured asteroids and are named for the children of Ares in Greek mythology.

Many of the planets have multiple moons, including Saturn with 60, Neptune with 13, and Uranus with 27.

Many of the planets are named for gods in Roman and Greek mythology, including Mars (the Roman name for Ares), Venus (the Roman name for Aphrodite), Mercury (the Roman name for Hermes), and Jupiter (the Roman name for Zeus).

Jupiter is the largest planet in the solar system. The red spot on the gas giant is a storm center that is larger than Earth.

Jupiter has a whopping 63 moons. The four largest moons are Ganymede, Callisto, Europa, and Io.

In 2005, astronomers discovered a planetary body beyond Pluto, which they named Eris. It is actually larger than Pluto.

Haumea is a pair of dwarf planets identified beyond Eris, but still within the solar system.


Ganymede would qualify for planetary status if it were not trapped in Jupiter's orbit.

Famous astronomers who helped define human understanding of the solar system include Johannes Kepler, Isaac Newton, Nicolaus Copernicus, and Galilelo Galilei.

Earth's surface is covered by three-quarters water.

Discovered in 1801, a dwarf planet exists between Mars and Jupiter named Ceres.

Beyond Pluto and Eris is a planetoid named Sedna. It takes more than 10,000 Earth years to orbit the sun.

An asteroid belt lies between Mars and Jupiter's orbits.

A planet is defined as a body that orbits on the same plane, but Pluto's shifting orbit helped downgrade it from planet to dwarf planet.