1 / 35

Structure of the Solar System

Structure of the Solar System. Where and why it is what it is. Laws of motion. Planets move around Sun Not always a given, Anthropic Earth-centered Ptolomaic cosmology Copernicus published his seminal work on his deathbed (1543) A case of publish and perish

jerold
Download Presentation

Structure of the Solar System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Structure of the Solar System Where and why it is what it is

  2. Laws of motion • Planets move around Sun • Not always a given, • Anthropic Earth-centered Ptolomaic cosmology • Copernicus published his seminal work on his deathbed (1543) • A case of publish and perish • De revolutionibus orbium celestium • Conservation of angular momentum • v1r1 = v2r2 = constant (for constant mass) • The two body problem

  3. Kepler’s Laws • Planets move around the Sun in elliptical orbits, with Sun as one of the foci • A radius vector sweeps out equal area in equal time • Squares of the periods of the revolutionof the planets are proportional to the cubes of their distance from the Sun

  4. Titius-Bode Law • Distances of planets from Sun • 0.4, 0.7, 1.0, 1.6, 2.8, 5.2, … • Can be formulated • R = 0.4 + 0.3k • K = 0, 1, 2, 4, 8, 16, 32 • 0.4, 0.7, 1.0, 1.6, 2.8, 5.2, … • Titius 1729-1776, Bode 1747-1826

  5. Titius-Bode Law Planet missing between Mars and Jupiter • At 2.8 au • Ceres discovered in 1801 at 2.77 au • Pallas, Juno, Vesta by 1804 • Exploded planet • No common origin point • Failed planet

  6. Titius-Bode Law • Okay for Uranus, not so good for Neptune (38 predicted vs 30 actual au) • No other correlation with planetary properties • Secondary effect after formation • Related to stable resonances of orbital periods • Planets have moved

  7. Asteroids • Total mass less than 5% of Moon • 1-2 Million asteroids with size > 1km • Asteroid belt • Gaps/concentrations due to resonances with Jupiter (Kirkwood Gaps) • Gaps at 2:1 (3.28 au) and 3:1 (2.50 au) • Concs at 1:1 3:2 (3.97 au) 4:3 (4.2 au) Vesta, Ceres, Moon

  8. 3:2 1:1 2:1 Orbital resonances • Fractional orbital periods have greater orbital stability to perturbation • Constructive or destructive interference • Gaps or concentrations

  9. Asteroids • Resonances and gaps

  10. Asteroids • Trojan Asteroids • Lagrange points • Gravitation = centripetal • L4 and L5 ± 60° • Equal gravity to Jup & Sol L1, L2, L3 unstable; L4,L5 stable

  11. Asteroids • Several hundred thousand discovered • 26 > 200 km • Solid rock bodies • Rubble piles • Visits by NEAR, Hayabusa • NEAR landed on Eros • Hayabusa landed on Itokawa • Plus flybys of other missions on way to Jupiter

  12. Asteroid Spectral Classes • Definition • Based on light reflectance (Albedo) • Spectral features • Spectral shape • Mineralogical features • e.g. olivine, pyroxene, water, … • Chapman 1975 • 3 types (C-carbonaceous, S-stony, and U) • Tholen 1984 • used spectra 0.31-1.06 µm • Types A-X (23)

  13. Mathilde Spectral Class • C-type (Most abundant 75 %) • Low albedo (0.03-0.10) • Strong UV absorption below 0.4 µm • Longer wavelengths featureless • Reddish • Water feature at 3 µm • Type 10-Hygeia • 4th largest asteroid

  14. Spectral Class • S Class (17%) • Moderately bright • Albedo 0.10-0.22 • Metallic Fe-Ni + magnesium silicate • Spectrum has steep slope < 0.7µm • Absorption features around 1 and 2 µm • Largest is 15 Eunomia (330 km diam) Ida + Dactyl

  15. Spectral Class • M class (3rd abundant) • Metallic Fe-Ni • Moderately bright (0.10-0.18) • Spectrum is flat to reddish • Absorption features at 0.55 and 0.75 µm • 16 Psyche (330 km) 16 Psyche

  16. Asteroids • Compositional trends? • Igneous inside 2.8 au (S class) • Metamorphic around 3.2 au (M class) • Primitive outside 3.4 au (C class)

  17. Origin of asteroid belt • Failed planet • Meteorites • Iron meteorites from core • Pallasites show mantle olivine • Igneous achondrites • Crustal carbonaceous chondrites • But not from single body • Oxygen isotopes, chemistry

  18. Origin of asteroid belt • Planetoids form in early SS • Coalesce to form planets • Presence of Jupiter • Pumped up the eccentricities • Limits growth • Many small bodies • No planet at 2.8 au

  19. Near-Earth asteroids • Apollos, Atens and Armors • Few thousand > 1km • 107 10-100m • 1036 Ganymed, 433 Eros • Source of meteorites? • Eros could survive 50-100 Myr • 5% chance of hitting Earth

  20. Spectrophotometric Paradox • Most common meteorites are chondrites • Parent body apparently absent • 3628 Boznemcová • 8km body with Ord-chondrite spectrum • Of 35 NEA, 6 have Ord-chondrite spectra • Plus 10% of Main Belt asteroids of size ≈1km • Chondrites dominate meteorites, • But not asteroids

  21. Asteroids to Meteorites • Relative frequency of meteorites depends on efficiency of delivery • Meteorites unlikely to be sourced from deep within asteroid belt • Asteroids must be close to resonances to supply meteorites into Earth-crossing orbit • 6 Hebe near 3:1(2.50 au) • Source of H-Chondrites + IIE Irons

  22. Missing Olivine Meteorites • Iron Meteorites • Cores • Pallasites • Core-mantle • Achondrites, Chondrites • Crust • Where’s the mantle olivine?

  23. Individual asteroids • 1 Ceres • Largest 933 km diameter • 2.7 g/cm3 • 2.77 au • C class • 9/13 largest asteroids similar

  24. Individual asteroids • 4 Vesta • Irregular shape (460 km across) • 3.7 g/cm3 • Intact differentiated crust (basalt) • Source of HED meteorites (4.560 Gyr) • 460 km crater, 13 km deep • Two more large craters (100 km+)

  25. Individual asteroids • 433 Eros • S class • 2nd largest NEA • 33x13x13 km • Density 2.5 ± 0.8 km • Coherent rather than rubble pile

  26. Individual asteroids • NEAR Lands on Eros - 2001 • Boulders on surface from 250 m 5 m

  27. Individual asteroids • 25143 Itokawa (1998) • S class • 500 m long • 2.0 g/cm3 • Rubble pile Hayabusa (Muses-C)

  28. Individual asteroids • Visits to Mathilde, Gaspra, Ida • Ida has satellite (Dactyl) NEAR Mission

  29. Interplanetary dust • Sources • Asteroids (5 km/s) • Comets (20-60 km/s) • Interstellar grains? • 10,000 tons/year to Earth • Fluffy grains can survive atmospheric entry • Many carbonaceous

  30. Moving Giant Planets • Jupiter moved sunwards depleting asteroid belt beyond 4 au • Saturn, Uranus, Neptune move out • Saturn now in 2:1 resonance with Jupiter • Produced by bombardment of centaurs

  31. Centaurs • Between Saturn and Uranus • 2060 Chiron - 1977 • 182 km • Dark-grey-black object (albedo 0.1) • Similar in size and colour to Phoebe (Sat Moon) • Orbit 8.5 - 19 au • Fits definition of comet • 5145 Pholus - 1992 • 185 km, red • Nessus, Asbolus, Chariklo

  32. Moving Giant Planets • Neptune plows into and depletes inner zone of Kuiper Belt (30-35 au) • Pluto swept into a 3:2 orbital resonance at high eccentricity and inclination

  33. Moving Giant Planets • can throw KBO out to the Oort Cloud • Only few % retained from Jupiter • Rest lost • 5-10% from Saturn • 10-40% from Uranus • 40% from Neptune • Can throw out Rocky and Icy bodies • Oort cloud primitive? • Throws objects in • The late heavy bombardment for inner SS

  34. Solar System • Dynamic • Many time scales • 4 Vesta has survived 4.56 Gyr • But Exposure ages of HED meteorites 5-80 Myr • Survival time of some asteroids • 50,000 years

  35. Near Earth Asteroid Orbits • http://neo.jpl.nasa.gov/orbits/

More Related