Driver's Fabulous Fourth Grade

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4.7 Solar System

  1. Early astronomers believed that Earth was the center of the universe and all other heavenly bodies orbited around Earth. 
  2. We now know that our sun is the center of our solar system and eight planets, a handful of dwarf planets, 170 moons, dust, gas, and thousands of asteroids and comets orbit around the sun.
  3. Our solar system is made up of eight planetsMercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. 
  4. Mercury, Venus, Earth, and Mars are considered terrestrial planets
  5. Jupiter, Saturn, Uranus, and Neptune are called gas giants.
  6. Mercury is closest to the sun and is a small, heavily cratered planet.  Mercury looks like our moon.  Since Pluto’s reclassification from planet to dwarf planet, Mercury is now the smallest planet in our solar system.
  7. Venus is second from the sun.  It is similar to Earth in size and mass, and has a permanent blanket of clouds that trap so much heat that the temperatures on  the surface of Venus are hot enough to melt lead.
  8. Earth is third from the sun.  Earth’s atmosphere, the liquid water found on Earth, and its distance from the sun, among many other factors, make Earth a haven for life. 
  9. Mars is fourth from the sun.  The atmosphere on Mars is thin and there is a vast network of canyons and riverbeds on the red planet.  Scientists hypothesize that Mars once supported a wet, warm Earth-like climate. 
  10. Jupiter is fifth from the sun. Jupiter is the largest planet in the solar system and is considered a gas giant.  Jupiter has no solid surface.
  11. Saturn is sixth from the sun.  Early scientists thought Saturn was the only planet with rings, but we now know that all four gas giants have rings.
  12. Uranus is seventh from the sun.  Uranus is a gas giant.
  13. Neptune is eighth from the sun.  Neptune appears blue through telescopes and is a gas giant.
  14. The eight planets sorted by size from largest to smallest are Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, and Mercury. 
  15. Pluto is no longer included in the list of planets in our solar system due to its small size and irregular orbit. 
  16. A new class of objects called “dwarf planets” was identified in 2006.
  17. A dwarf planet has not “cleared the neighborhood” around its orbit, which means it has not become gravitationally dominant and it shares its orbital space with other bodies of similar size.