1. Grade 6 – Cluster 4

2. Our understanding about the universe changes over time. New information can causes us to rethink what we know and reevaluate how we understand the universe. The History of Space

4. Over time, objects categorized as planets have changed. History of Space

5. The ancient Greeks believed the Earth's moon and sun were planets along with Mercury, Venus, Mars, Jupiter, and Saturn. Earth was not considered a planet, but thought to be the central object around which all the other celestial objects orbited. History of Space

6. By the 17th century, astronomers realized that the sun was the object around which all the planets orbit, and that the moon is not a planet, but a satellite (moon) of Earth. History of Space

8. Uranus was added as a planet in 1781 and Neptune was discovered in 1846. History of Space

9. Pluto, discovered in 1930, was identified as the ninth planet. History of Space

10. What Makes a Planet According to the International Astronomical Union? PlanetDwarf Planet Is in orbit around the sun. XX Has sufficient mass to assume a nearly round shape. XX Is not a satellite (moon). XX Has cleared the neighbourhood of its orbit. X Has not cleared the neighbourhood of its orbit. X History of Space *** This will be on a test

11. The official names of planets and their moons are governed by an organization called the International Astronomical Union (IAU). The IAU was established in 1919. How did the planets get their names?

13. Our Planets - Mercury Mercury is only slightly larger than Earth's moon.

14. Like the moon, Mercury has very little atmosphere to stop impacts and it is covered with craters. Our Planets - Mercury

15. Mercury's dayside is super-heated by the sun, but at night temperatures drop hundreds of degrees below freezing. Ice may even exist in craters. Our Planets - Mercury

16. Mercury's egg- shaped orbit takes it around the sun every 88 days. Our Planets - Mercury

17. Venus is only a little smaller than Earth. Our Planets - Venus

18. One day on Venus lasts as long as 243 Earth days (the time it takes for Venus to rotate or spin once). Our Planets - Venus

19. Venus is a rocky planet, also known as a terrestrial planet. Venus' solid surface is a cratered and volcanic landscape. Our Planets - Venus

20. Venus makes a complete orbit around the sun in 225 Earth days. Our Planets - Venus

21. If the sun were as tall as a typical front door, Earth would be the size of a nickel. Our Planets - Earth

22. One day on Earth takes 24 hours (this is the time it takes the Earth to rotate or spin once). Earth makes a complete orbit around the sun (a year in Earth time) in about 365 days. Our Planets - Earth

23. Earth's atmosphere protects us from incoming meteoroids, most of which break up in our atmosphere before they can strike the surface as meteorites. Our Planets - Earth

24. Earth is the perfect place for life. Our Planets - Earth

25. If Earth were the size of a nickel Mars would be about as big as an aspirin tablet. Our Planets - Mars

26. One day on Mars takes just a little over 24 hours (the time it takes for Mars to rotate or spin once). Our Planets - Mars

27. Mars makes a complete orbit around the sun (a year in Martian time) in 687 Earth days. Our Planets - Mars

28. At this time in the planet's history, Mars' surface cannot support life. A key science goal is determining Mars' past and future potential for life. Our Planets - Mars

29. If Earth would be the size of a nickel and Jupiter would be about as big as a basketball. Our Planets - Jupiter

30. One day on Jupiter takes about 10 hours (the time it takes for Jupiter to rotate or spin once). Our Planets - Jupiter

31. Jupiter makes a complete orbit around the sun (a year in Jovian time) in about 12 Earth years (4,333 Earth days). Our Planets - Jupiter

32. Jupiter is a gas-giant planet and does not have a solid surface. However, it is predicted that Jupiter has an inner, solid core about the size of the Earth. Our Planets - Jupiter

33. Jupiter's Great Red Spot is a gigantic storm (bigger than Earth) that has been raging for hundreds of years. Our Planets - Jupiter

34. Saturn is the second largest planet, and comparable in size to Jupiter. Our Planets - Saturn

35. One day on Saturn takes 10.7 hours (the time it takes for Saturn to rotate or spin once). Our Planets - Saturn

36. Saturn makes a complete orbit around the sun (a year in Saturnian time) in 29 Earth years. Our Planets - Saturn

37. Saturn cannot support life as we know it. However, some of Saturn's moons have conditions that might support life. Our Planets - Saturn

38. Earth would be the size of a nickel and Uranus would be about as big as a baseball. Our Planets - Uranus

39. One day on Uranus takes about 17 hours (the time it takes for Uranus to rotate or spin once). Our Planets - Uranus

40. Uranus makes a complete orbit around the sun (a year in Uranian time) in about 84 Earth years. Our Planets - Uranus

41. Like Venus, Uranus has a retrograde rotation (east to west). Unlike any of the other planets, Uranus rotates on its side, which means it spins horizontally. Our Planets - Uranus

42. If Earth would be the size of a nickel and Neptune would be about as big as a baseball. Our Planets - Neptune

43. One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once). Our Planets - Neptune

44. Neptune makes a complete orbit around the sun (a year in Neptunian time) in about 165 Earth years (60,190 Earth days). Our Planets - Neptune

45. At times during the course of Neptune's orbit, dwarf planet Pluto is actually closer to the sun, and us, than Neptune. This is due to the unusual elliptical (egg) shape of Pluto's orbit. Our Planets - Neptune

46. Is Pluto a planet? Our Planets - Pluto