Solar System and Planets Notes

Terrestrial Planets

  • The first four planets (Mercury, Venus, Earth, and Mars) are called terrestrial planets because they are similar to Earth.
  • The inner planets in order from the sun are Mercury, Venus, Earth, and Mars.
  • Compared to the outer planets, the inner planets are much smaller in size.
  • The structure of the inner planets includes a crust, mantle, and core.
  • All inner planets have a rocky surface.
  • Inner planets do not have rings.
  • The inner planets are generally warmer in temperature than the outer planets.
  • The inner planets have few moons, ranging from 0 to 2.
  • Mercury is the closest planet to the sun.
  • Venus is called "Earth's twin" because it is similar in size to Earth.
  • Mars is known as "the red planet" due to the rocks on its surface.
  • Earth is the perfect planet for life because of its distance from the sun and its perfect atmosphere.
  • Mars has the tallest volcano in the solar system, Olympus Mons.
  • Venus has the hottest surface of any planet because of the greenhouse effect.
  • Mercury is covered in craters due to meteorite collisions and lack of atmosphere.
  • Mercury has the shortest year.
  • Water exists on Mars in the form of ice caps, found at the poles.
  • Venus has a day that is longer than its year.
  • Venus is the brightest planet viewed from Earth.
  • Mars possibly had liquid water in the past.
  • Venus' atmosphere is thick with carbon dioxide.

Gas Giants

  • The area that separates the inner and outer planets is called the asteroid belt.
  • The four gas giants in order from the sun are Jupiter, Saturn, Uranus, and Neptune.
  • The gas giants are primarily made up of hydrogen and helium.
  • Gas giants do not have a solid surface.
  • Jupiter is the largest planet in our solar system.
  • The Great Red Spot is a storm on Jupiter.
  • Scientists believe the most likely place to find life in our solar system (besides Mars and Earth) is on Jupiter's moon, Europa, due to its icy crust above saltwater.
  • All four gas giants have rings.
  • Rings are made of rock, dust, and ice.
  • Saturn has the most moons.
  • Saturn has the lowest density of any planet and would float in water.
  • Saturn's rings are the most distinct.
  • Uranus and Neptune are bluish in color due to methane gas.
  • Uranus was the first planet discovered with a telescope.
  • Scientists believe Uranus is tilted on its side because it was hit by a large object.
  • The Great Dark Spot was a storm on Neptune.
  • Neptune has the longest year.

Dwarf Planets, Kuiper Belt, Exoplanets, Comets, Meteors

  • A dwarf planet is a type of planet that is too small to clear its orbit as it moves.
  • The four characteristics of a planet are:
    • Spherical shape
    • Orbits a star
    • Not a star or moon
    • Enough gravity to clear its orbit
  • There are five dwarf planets.
  • Pluto, Haumea, and MakeMake are dwarf planets found after Neptune.
  • Ceres is a dwarf planet found after Mars; it used to be considered an asteroid.
  • The area of thousands of objects beyond Neptune's orbit is called the Kuiper Belt.
  • Exoplanets are planets orbiting a star other than the sun; they are detected by studying the gravity of the star.
  • The largest of the rocky bodies that orbit the sun is an asteroid.
  • Comets are small bodies of ice, rock, and dust that give off gas in the form of a tail.
  • Halley's Comet is the most famous comet that passes Earth every 76 years.
  • The core of a comet consists of rock, metal, and ice.
  • The coma is the cloud of dust that surrounds the nucleus of a comet.
  • The tail is formed when sunlight causes ice within the comet to change to gas.
  • The Oort cloud is a spherical region of billions of comets that surrounds our solar system.
  • Long-period comets take more than 200 years to orbit the sun.
  • Short-period comets take less than 200 years to orbit the sun.
  • A meteoroid is a small rocky body in the solar system (smaller than asteroids).
  • A meteor is also called a "shooting star" and burns up in Earth's atmosphere.
  • A meteorite is any part of a meteor that doesn't burn up and ends up hitting Earth.

Planets in Order and Their Roman God Namesakes

  • The planets in order from the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune (Mnemonic: "My Very Educated Mother Just Served Us Nachos").
  • Planets named after Roman gods:
    • Mercury: Messenger god
    • Venus: God of love and beauty
    • Mars: God of war
    • Jupiter: King of the gods
    • Saturn: God of agriculture
    • Uranus: God of the sky
    • Neptune: God of the sea