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Origin-of-SS.ppt
- 1. Origin of the Solar System
- 2. Stars spew out 1/2 their mass as gas & dust as they die
- 3. In the interstellar medium, dust and gas coalesces into clouds
- 4. New generations of stars (and their planets, if any) form in these clouds
- 5. • Interstellar cloud of gas & dust collapsed under its own gravity • Prediction: protoplanetary nebulae should be observed • Explains all of the major features of solar system, and also the exceptions • Observations continue to support this theory Nebular theory
- 8. Protoplanetary disks last for only about 1-10 million years
- 11. The next billion years: Debris disks • Gas and fine dust blows away after ~ 10 million years • Jupiter must have formed by then • Older stars have ‘debris disks’ around them • Need a supply of larger objects to regenerate the dust that gets blown away • evidence of planets forming around other stars • Debris disks are analogous to the Oort cloud and Kuiper belt of comets, and the asteroid belt
- 12. Debris disks around stars > 100 million years old are very common!
- 13. (artist’s drawing of a debris disk)
- 14. Zodiacal light
- 15. Any GOOD hypothesis about the origin of the solar system must explain most - if not all - of its characteristics: 1. All of the planets orbit the sun in the same direction, and in the same plane 2. The planets closest to the sun are small and rocky, have few moons 3. The planets further from the sun are large and contain more gas and icy materials 4. Most of the Moons orbit their planets in the same direction as the planets orbit the sun 5. Oldest meteorites are about 4.566 billion years old 6. Planetary surfaces are all younger than the oldest meteorites
- 16. Relative sizes of the planets
- 17. Sizes of the planets relative to Sun
- 18. Sun-planet distance (relative to Earth: AU) Mercury 0.4 AU Venus 0.7 Earth 1.0 Mars 1.5 Jupiter 5.2 Saturn 9.5 Uranus 19 Neptune 30 1 AU = 150 million km
- 19. Other residents of the solar system: 1. Dwarf planets diameter = 1000-3000 km, smaller than Moon, orbit the sun
- 20. Other residents of the solar system 2. Asteroids - rocky, d < 1000 km, orbit the sun
- 21. Asteroid belt
- 22. Asteroids are really quite rare…
- 23. 3. Comets - rock & ice, wide range of sizes (~10 m to 100 km) Other residents of the solar system
- 24. Other residents of the solar system 4. Moons - orbit planets, some are larger than Mercury
- 25. Asteroids and comets are leftover planetesimals Some moons are captured planetesimals
- 26. Other residents of the solar system 5. Meteoroids - small fragments of asteroids that enter earth’s atmosphere (dust to boulder sized)
- 27. Meteor!
- 28. Zodiacal light
- 29. Any GOOD hypothesis about the origin of the solar system must explain most - if not all - of its characteristics: 1. All of the planets orbit the sun in the same direction, and in the same plane 2. The planets closest to the sun are small and rocky, have few moons 3. The planets further from the sun are large and contain more gas and icy materials 4. Most of the Moons orbit their planets in the same direction as the planets orbit the sun 5. Oldest meteorites are about 4.566 billion years old 6. Planetary surfaces are all younger than the oldest meteorites
- 30. Protoplanetary disks last for only about 1-10 million years
- 33. H, He gas is present throughout the disk Icy compounds and rock/metal Rock & metal ice line Condensation: gas becomes solid
- 34. What are the planets made of? Element how many atoms gas or solid at (total) Earth Jupiter ________________________________________________ Hydrogen 705,700 gas gas Helium 275,200 gas gas Carbon 3,032 gas soot (solid) Nitrogen 1,105 gas ice Oxygen 5,920 H2O gas H2O ice Silicon 653 rock rock Iron 1,169 metal metal
- 35. Planet formation: Terrerstrial vs. giant planets Giant (“jovian”) 1. Lots of solids in the disk (cold > 5 AU) 2. Cores form from ice, rock and metal 3. Grow large, quickly (~1 million years) 4. Big enough to trap H and He gas from disk Terrestrial (“earth like”) 1. Very little solid material in disk at 1 AU 2. Form from rock and metal only 3. Grow slowly (~100 million years) 4. Too small to trap any gas from disk
- 36. Connecting the dots: From planet formation to early Earth Computational astrophysics meets field geology!
- 37. 1 million years 10 million years >100 million years, 3.8 billion years ago Hot+Dry (H2O gas) H2O ice Jupiter habitable zone
- 38. Terrestrial planets form by accretion of solids Dust >rocks >planetesimals >embryos >planets
- 39. The Moon-Forming Event •A protoplanet the size of Mars (1/10 Earth’s mass) struck Earth, forming t Moon 4.5 billion years ago •Oceans boiled away, silicate-vapor atmosphere for at least 1 Myr •Earth had already differentiated into core & mantle structure by this time t=0 : IMPACT! 6 minutes 20 minutes 32 minutes
- 41. But what if you don’t know: • the initial number of parent & daughter atoms? • how much of the P & D’s have entered or left the rock?
- 42. Solution: Isochron dating, requires a 4th measurement (the amount of a stable isotope of one of the elements) 48.8 Gyr Slope = D(now)/P(now)
- 43. melt solid
- 44. Make measurements for different minerals in rock. If data are linear, there is a strong correlation between: •The amount of P in each sample •The extent to which the sample has been enriched in D
- 46. Formation of Jovian Planets: Fast! (< 10 Myr) Core accretion: icy planetesimals clump together first Gravitational instability: dense clump of nebular gas forms first
- 47. The Nebular theory predicts most other sun-like stars should have planets Do they?
- 48. 358 planets have been found around other stars!!! http://www.exoplanets.org
- 49. Detecting planets around other stars: Doppler method
- 50. Transit method (Kepler Mission)