2. Coming Down to Earth… Antares – a huge red giant Betelgeuse – a large red giant Aldebaran – a red giant Rigel – blue star Arcturus – red giant

3. Arcturus – a large yellow star Pollux – a medium- large yellow star Sirius – a white star The Sun – an average size yellow star Coming Down to Earth…

4. The Sun compared to the planets of the solar system

5. What We Know About Our Solar System

6. A. 1 Sun and 8* 8* planets spread across a flat disk B. All of the planets orbit in the same flat plane as the sun. C. All of the planets orbit in the same direction as the sun rotates. *See “What about Pluto?” at the end.

7. Planets all orbit in the same flat orbital plane.

8. D. The sun rotates more slowly than expected. (Usually there is an increase in angular momentum near the center of a spinning system.) E. The solar system is loaded with rare elements (Pb, Au, U, Pt, etc.) What We Know About Our Solar System

9. The Terrestrial Planets F. The four inner planets are small and rocky and have very thin atmospheres.

10. The Terrestrial Planets

11. F. The four inner planets are small and rocky and have very thin atmospheres.

12. The Asteroid Belt Where Meteorites Come From

14. The Jovian Planets G.The outer planets are large, with thick, dense atmospheres.

15. The Jovian Planets …are also called the “Gas Giants”

16. Comparison of the Size of the Planets Jovian Planets Terrestrial Planets

17. The Jovian Planets G.The outer planets are much larger than the inner planets.

18. ***Any good hypothesis has to explain all of these facts.***

19. Is Pluto Really a Planet??

20. Pluto’s Orbit is Tilted Out of the Solar System’s Equatorial Plane

21. The Kuiper Belt Home to Pluto and the Dwarf Planets

22. Planet Eris – The Tenth Planet?? Time lapse of Eris against the background of the Constellation Orion. Eris is circled in each photo.

23. Planet Eris – The Tenth Planet?? Eris with the Sun in the far distance. Eris is a little bigger than Pluto, but 3 times as far from the sun.

24. Is Pluto Really a Planet??

25. Object 2003 UB 313 was officially named Eris on September 13, 2006. (for the Greek goddess of “Strife and Discord”) is Pluto’s moon, but is over half as big as Pluto. is the largest object in the asteroid belt. “Pluto & the 3 Dwarfs”

26. The Final Decision – August 24, 2006 - The International Astronomical Union decides that Pluto is no longer a planet. Pluto, Eris, and Ceres are classified as Dwarf Planets. (Sedna is the next likely candidate to be added.)

27. More dwarf planet candidates As of September 17, 2008, Eris, Pluto, Makemake, Haumea and Ceres are classified as Dwarf Planets. (Ceres is in the Asteroid Belt.) Sena, Orcus, Quaoar and Varuna are all likely to be named dwarf planets. There are 40 other known possible dwarf planets.

28. The New Solar System 8 Planets 5 Dwarf Planets (so far…) Eris

29. The Oort Cloud Where Comets Come From

30. Comet Halley – due back in 2061

31. Excellent, Excellent!! Excellent photos and illustrations courtesy of NASA

32. Comparison of the Size of the Planets Jovian Planets Terrestrial Planets Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto