Planetary System

1. Planetary System ASTR 1420 Lecture 15 Section 3.3

2. Solar System Overview

3. Put it on a tangible scale about 1/3 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Mercury = a quarter at the Stegeman Coliseum

4. So much of empty space… about a mile away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Earth = an apple at the intramural field

5. So much of empty space… ~3 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Asteroids = millions of planktons scattered around the Loop 10 (perimeter road)

6. So much of empty space… ~5 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Jupiter = a classroom desk near the west-end of Athens

7. So much of empty space… ~10 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Saturn= a classroom desk near Bogart on highway 316

8. So much of empty space… ~20 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Neptune = a basketball near the Gwinnett county airport (Lawrenceville)

9. So much of empty space… ~30 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Pluto = a penny at the I-85 / GA-316 intersection

10. So much of empty space… ~40-60 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA K-B objects = millions of microbes + small insects scattered around northern Georgia

11. So much of empty space… ~200,000 miles away If we scale down everything by 100 million times… Sun = a small truck at the Physics Building at UGA Nearest Star = another truck at the distance to the Moon

12. Solar System Overview

13. Features of Solar System Orderly motions of large objects Two major types of planets Lots of smaller bodies Some exceptions Venus Uranus Earth’s Moon

14. Orderly Motions All planets orbit the Sun in the same direction All planets are in the same plane All planets orbit in nearly circular orbits Most planets’ rotation direction = orbital direction

15. Two Groups of Planets • Earth-like Planets (Terrestrial Planets, rocky planets, inner planets) • Mercury, Venus, Earth, & Mars • metal and rock  average density 2-3 times higher than the density of liquid water • Solid surface and thick atmosphere • Jupiter-like Planets (Jovian Planets, Gas giant planets, outer planets) • Jupiter, Saturn, Uranus, Neptune • Gas : hydrogen, helium + methane, ammonia, ice • No solid surface • Low density : Saturn’s density < 1.0 !! • Two outer planets have higher content of metal+rock What about Pluto?

16. Small Bodies Asteroids, comets, K-B objects asteroids : metals and rocks comets : largely ices + rocks and metal K-B objects : similar to comets Oort cloud : similar to comets?

17. Kuiper Belt Objects Some larger ones = dwarf planets  large enough to be circular shaped…

18. Moons (satellites) • Objects that orbit planets or other objects. • Jupiter : 63 • Saturn : 62 (150) • Moons of jovian planets contain lots of ice  snowline! • Large moons are potential habitable worlds

19. Why? The order with well defined characteristics… • There must be a good reason. • It is related to the way of stars and their planets being formed!

20. Lots of clouds in the Galaxy

21. Formation of Planetary System (nebular theory) collapsed to a nearly 1/1,000,000 of the initial size • Contraction and disk formation Once the collapse begins, nebula would heat up, spin faster, and flatten… Conservation of Energy (heating up) : gravitational potential energy  heat energy Conservation of angular momentum (spin up)

22. Composition of Clouds

23. Formation of Planetary System • Condensation (opposite of melting) : High temperatures in the inner region  materials only with high condensation temperatures can turn to solids (metals and rocks). Outer region is much cooler  materials with lower condensation temperatures can turn to solids also (ices, rocks and metals)  more solids than the inner region! Hydrogen and Helium remain as gas everywhere in the disk.

24. Formation of Planetary System • Accretion of solids Pebbles  rocks  boulders  … planetesimals (~100 km size) … this process over a few million years… • Collisions b/w planetesimals(some stuck, some shatter) • Formation of rocky planets (inner) and some ice-rocky planets (outer) • Gas accretion in the outer area (why not inner?)  Jovian planets!

25. Formation of Planetary System • Moon formations around Jovian planets  in a disk surrounding a Jovian planet (similar to the way planets are formed)…

26. Formation of Planetary System • Clearing the Disk Remaining gas will be blown away by solar wind… Rocks remain, but gradually being cleared by planets or collide among themselves…

27. Is this happening at other stars? Yes!  many habitable worlds in the Universe!! Young stars in their early formation showing a disk (dark shade)

28. Planetary system formation simulation http://www.youtube.com/watch?v=jhYEQgLW5NM

29. In summary… Important Concepts Important Terms Terrestrial planets Jovian planets Kuiper Belt objects Oort Clouds Condensation/accretion Planetesimals • Planet formation (nebular theory) • Conservation of Energy • Conservation of angular momentum • Ordered structure of planets is a natural outcome of planet formation. • Chapter/sections covered in this lecture : 3.3 • Exoplanet Detection : next class!!