1. The Planets SPACE

2. Learning Goals  To be able to describe the planets of our solar system

3. Classifying a Planet  To be considered a planet, a celestial object must: 1. Orbit a star (such as the Sun) and no other celestial object 2. Contain enough mass so that its gravity pulls it into a round or spherical shape 3. Be able to clear other celestial objects out of its orbit

4. Planetary Motion - Revolution  All of the planets revolve, or travel around the Sun  The orbits are elliptical, or oval-shaped  Earth completes one revolution around the Sun in about 365 days, which we call 1 year  The other planets take different amounts of time to complete one revolution (Mercury – 88 days; Neptune – 164 years)

5.  Discovered in 1930

6. Planetary Motion - Rotation  Planets also rotate, or spin or turn on an axis  An axis is an imaginary line around which an object rotates  Earth’s axis runs from pole to pole  Most planets rotate in a west-to-east direction, similar to Earth  Venus rotates in the opposite direction

7. Planetary Motion - Rotation  Earth’s rotation causes our day and night  Earth completes one rotation every 24 hours, which is one day  The amount of time a planet takes to rotate is equal to the length of one day on that planet

8. Mercury

9.  Closest to the Sun  Hot days ( 430 °C ); Cold nights ( -170 °C )  Mercury is 0.38 AU from the Sun  Revolution of 88 days (= 1 year)  Rotates once every 59 days (= 1 day)  No moons  Temperatures range from -170 °C at night to 430 °C during the day  Mariner 10 first visited in 1974 & 1975, Messenger began orbiting in 2011

10. Venus

11.  Volcanoes (toxic atmosphere)  Brightest in night sky after Moon  Hottest planet (450 °C, max 480 °C)  Venus is 0.72 AU from the Sun  Revolution of 224.7 days  Rotation of 243 days  Diameter is 0.95 times Earth’s  No moons  Opposite rotation to Earth

12. Earth

13.  Liquid water  Sustains life  Earth is 1 AU from the Sun  Revolution of 365 days  Rotation of 24 hours  Diameter is 12, 740 km  1 moon (the Moon)  Temperatures range from -85 °C to 65 °C

14. Mars

15.  Red soil ( red planet )  Most studied planet  Evidence of water, volcanoes, glaciers in the past  Mars is 1.52 AU from the Sun  Revolution – 687 days (1.88 years); Rotation 24.6 hours  Diameter is 0.53 times Earth’s  2 moons (Phobos and Deimos)  Temperatures range from -133 °C to 27 °C  Mariner 4 flyby in 1965, 2 Viking landers in 1976, Mars Pathfinder in 1997, Mars Surveyor (2000’s), Mars Science Laboratory (2012)

16. Terrestrial Planets Relative Sizes

17. Jupiter

18.  Largest planet  Great Red Spot – giant hurricane  63 known moons (Io, Europa, Ganymede, Callisto)  Jupiter is 5.20 AU from the Sun  Revolution of 11.9 years  Rotation of 9.9 hours  Diameter is 11.0 times Earth’s  Temperature around -153 °C

19. Jupiter  Visited by Pioneer 10 in 1973, then Pioneer 11, Voyager 1 and 2, Ulysses, Cassini-Huygens, and Galileo orbited it for 8 years  1994, comet Shoemaker-Levy 9 was torn apart and pieces crashed into Jupiter

20. Saturn

21.  Over 1000 rings  62 known moons (Titan)  Saturn is 9.5 AU from the Sun  Revolution of 29.46 years  Rotation of 10.2 hours  Diameter is 9.4 times Earth’s  Temperature around -185 °C  Visited by Pioneer 11 (1979), Voyager 1 and 2, Cassini (recent)

22. Uranus

23.  Rotates on its side  Strong winds  Uranus is 19.2 AU from the Sun  Revolution of 83.75 years  Rotation of 17.2 hours  Diameter is 4 times Earth’s  27 moons and some rings (1977)  Temperature around -210 °C  Visited by Voyager 2 in 1986  Discovered as a planet in 1781

24. Neptune

25.  Predicted and then discovered in 1846  Neptune is 30 AU from the Sun  Revolution of 164.8 years  Rotation of 16.1 hours  Diameter is 3.9 times Earth’s  13 Moons and some rings  Temperature around -220 °C  Visited by Voyager 2 in 1989

26. Relative Size of Jovian Planets

27. Distances from Sun

28. Tilt of Planets

29. Dwarf Planets  A dwarf planet is a celestial object that orbits the Sun and has a spherical shape, but does not clear its orbit  Five recognized dwarf planets: Ceres, Pluto, Haumea, Makemake, Eris  Scientists estimate another 70 000 icy objects beyond Neptune  Pluto takes 248 years to orbit Sun, Eris takes twice as long

30. Asteroid Belt  An asteroid belt is located between the orbits of Mars and Jupiter  The dwarf planet Ceres is located in the asteroid belt

31. The Moon

32.  Earth’s only natural satellite  About 384,000 km from Earth  The moon revolves around Earth and rotates on its axis every 27.32 days  For this reason, we always see the same side of the moon  Diameter is 0.27 times Earth’s  Gravity is 1/6 of Earth’s  The Moon is responsible for tides on Earth

33. Success Criteria  I CAN describe the similarities and differences among the planets in our solar system