science - characteristics of planets

• Nebular theory


  The sun and planets are formed from a rotating disk of dust and gases
• Nebula


  A cloud of gas and dust in space that will form heavenly bodies over time
• Planets classified by type

  • Terrestrial planets
  • Jovian planets
• Terrestrial planets


  Also called the inner planets
• Inner/Terrestrial planets


  • Mercury
  • Venus
  • Earth
  • Mars
• Mercury


  • Nearest planet to the sun
  • Has many craters due to no atmosphere
  • Has no moons
  • One rotation is 58 days 15 hours 30 minutes
  • One revolution around the sun is 88 days
  • Considered the fastest planet
• Venus


  • Second planet from the sun
  • Brightest object in the sky besides the sun
  • Commonly referred to as the morning and evening star
  • Considered the twin planet of Earth
  • Hottest planet due to thick CO2 atmosphere and greenhouse effect
  • Clouds are mostly sulfuric acid
  • Rains are acid rain
  • Surface has volcanoes and mountains
  • First planet studied with space in 1962
  • No moons
  • Gravity as strong as Earth
  • One rotation is 116 days 18 hours
  • One revolution is 225 days
  • Rotates very slowly, only twice per year
• Earth


  • Third planet from the sun
  • The only known living planet
  • Rich in liquid water to support life
  • Has an atmosphere that supports and protects life
  • Atmosphere burns most meteors before reaching surface
  • Has one large moon
  • One rotation is 23 hours 56 minutes
  • One revolution is 365.25 days
• Mars


  • Known as the red planet
  • Surface appears red/yellow due to iron oxide
  • Atmosphere is 18% and mostly CO2
  • Has water in atmosphere but not enough to form clouds
  • One rotation is 24 hours 37 minutes
  • One revolution is 687 days
  • Has the largest volcano in the solar system, Olympus Mons
  • Gravity is 2/5 as strong as Earth
  • Has two irregularly shaped moons, Phobos and Deimos
• Mercury, Venus, Earth, and Mars are called terrestrial planets because they have rocky surfaces and metal cores
• Asteroid belt


  Group of asteroids found between the orbits of Mars and Jupiter, separating the terrestrial and Jovian planets
• Outer/Jovian planets


  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• Jupiter


  • Largest gaseous planet
  • More than 11 times the size of Earth
  • Generates strong gravitational force
  • Atmosphere is hydrogen, helium, methane, ammonia, water vapor
  • Has a faint dust ring
  • Has at least 63 moons, including the 4 Galilean moons of Ganymede, Callisto, Europa, and Io
  • Ganymede is the largest moon in the solar system
  • Io has active volcanoes
  • Callisto is mostly rock and ice
  • Has a large counterclockwise rotating storm called the Great Red Spot
  • One rotation is 9 hours 56 minutes
  • One revolution is 12 years
• Saturn


  • Second largest planet
  • Lowest density of the planets
  • 9.5 times larger than Earth
  • One rotation is 10 hours 39 minutes
  • One revolution is 29 years
  • Atmosphere is hydrogen, helium, methane, water vapor
  • Has at least 31 moons, the largest being Titan
• Uranus


  • Third largest planet
  • Has a system of 11 thin dark rings
  • Atmosphere is hydrogen, helium, methane which gives it a bluish-green color
  • Radiates the same amount of solar energy it receives
  • Axis of rotation is tilted 84 degrees, so its north pole faces the sun for half its 84-year revolution
  • One rotation is 17 hours 14 minutes
  • One revolution is 84 years
  • Gravity is a little stronger than Earth
  • Has at least 21 moons, the largest being Titania
• Neptune


  • Fourth largest planet
  • Has an elliptical orbit
  • Atmosphere is mostly methane, giving it a bluish-green color
  • Has a dark storm called the Great Dark Spot
  • Has the fastest winds in the solar system
  • Has at least 11 moons, the largest being Triton
  • One rotation is 16 hours 6 minutes
  • One revolution is 165 years
• Planets in order from closest to farthest from the sun

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• Dwarf planets


  Smaller planets that do not meet the full criteria to be considered a regular planet, such as Pluto and Ceres
• Pluto


  • Was previously considered the 9th planet until 2006, when it was reclassified as a dwarf planet due to the discovery of the Kuiper Belt beyond its orbit
• Ceres


  • Largest asteroid, orbiting between Mars and Jupiter
  • Considered a dwarf planet due to its self-gravity making it round
• A person who studies the heavenly bodies is called an astronomer