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Earth

Planet Type: Terrestial
Year Length: 365 Earth Days

The only place we know of so far that’s inhabited by living things
Also the only planet with liquid water on the surface.

Venus

Planet Type: Terrestial
Year Length: 225 Earth Days

Venus spins slowly in the opposite direction from most planets
Venus spins slowly in the opposite direction from most planets

Mars

Planet Type: Terrestial
Year Length: 225 687 Earth Days

Mars is a dusty, cold, desert world with a very thin atmosphere
There is strong evidence Mars was, years ago,wetter and warmer.

Mercury

Planet Type: Terrestial
Year Length: 88 Earth Days

The smallest planet, only slightly larger than Earth's Moon.
Also the fastest planet circling the Sun every 88 Earth days.

Jupiter

Planet Type: Gas Giant
Year Length: 4333 Earth Days

Twice as massive than the other planets of our solar system combine.
The giant planet's Great Red spot is a centuries-old storm bigger than Earth.

Saturn

Planet Type: Gas Giant
Year Length: 10,759 Earth Days

Adorned with a dazzling, complex system of icy rings, Saturn is unique in our solar system.
The other giant planets have rings, but none are as spectacular as Saturn's.

Uranus

Planet Type: Ice Giant
Year Length: 30,687 Earth Days

Uranus is about four times wider than Earth.
Uranus is an ice giant. Most of its mass is a hot, dense fluid of "icy" materials – water, methane and ammonia

Neptune

Planet Type: Ice Giant
Year Length: 60,190 Earth Days

Neptune is the most distant major planet - is dark, cold and whipped by supersonic winds.
The first planet located through mathematical calculations, rather than by telescope.

What is a Planet?

This seemingly simple question doesn't have a simple answer. Everyone knows that Earth, Mars and Jupiter are planets. But both Pluto and Ceres were once considered planets until new discoveries triggered scientific debate about how to best describe them—a vigorous debate that continues to this day.

The most recent definition of a planet was adopted by the International Astronomical Union in 2006. It says a planet must do three things

  • It must orbit a star (in our cosmic neighborhood, the Sun)
  • It must be big enough to have enough gravity to force it into a spherical shape
  • It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun
  • Planets in our Solar System

    There are more planets than stars in our galaxy. The current count orbiting our star: eight. The inner, rocky planets are Mercury, Venus, Earth, and Mars. NASA's newest rover — Perseverance — landed on Mars on Feb. 18, 2021.

    The outer planets are gas giants Jupiter and Saturn and ice giants Uranus and Neptune. Beyond Neptune, a newer class of smaller worlds called dwarf planets reign, including longtime favorite Pluto. Thousands more planets have been discovered beyond our solar system. Scientists call them exoplanets (exo means "from outside").

    Dwarf Planets

    The key difference between a planet and a dwarf planet is the kinds of objects that share its orbit around the Sun. Pluto, for example, has not cleared its orbit of similar objects while Earth or Jupiter have no similarly-sized worlds on the same path around the Sun. Dwarf planets are generally round (Haumea looks like an overinflated football) and orbit the Sun.

    There are likely thousands of dwarf planets waiting to be discovered beyond Neptune. The five best-known dwarf planets are Ceres, Pluto, Makemake, Haumea, and Eris. Except for Ceres, which lies in the main asteroid belt, these small worlds are located in the Kuiper Belt. They’re considered dwarfs because they are massive, round, and orbit the Sun, but haven't cleared their orbital path.