Transcript No Slide Title
Formation of Our Solar System
Image: Lunar and Planetary Laboratory: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=178
Some data to explain:
1. Planets isolated 2. Orbits ~circular / in ~same plane 3. Planets (and moons) travel along orbits in same direction…. same direction as Sun rotates (CCW)
Venus slowly rotates CW Uranus on its side Pluto on its side – captured asteroid?
Moons go CCW around planets (few exceptions)
Lunar and Planetary Institute image at http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=175
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Solar System is highly differentiated
Terrestrial planets
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Slow rotators, few or no moons Gas Giants
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Fast rotators, many moons Asteroids
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Old Different from rocky or gaseous planets Comets
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Old, icy Do not move on same plane as planets
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Planets, most moons, and asteroids revolve around the Sun in the same direction (CCW)
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They all move in ~ circular orbits
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Pluto-special case
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Orbit is highly inclined (18
°
) oval shape
Some more data to explain:
4. Most planets rotate in this same direction Mercury 0 ° 25 ° Venus 177 ° Earth 23 ° Mars Jupiter 3 ° Saturn 27 ° Uranus 98 ° Neptune 30 ° NASA images edited by LPI
And some more data to explain:
5. Solar System highly differentiated:
Terrestrial Planets (rocky, dense with density ~4-5 g/cm3) Jovian Planets (light, gassy, H, He, density 0.7 2)
Images: Lunar and Planetary Laboratory: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=178
How Did We Get a Solar System?
Image: LPI
Active region of Star formation in the Large Magellanic Cloud (LMC) – satellite galaxy of Milky Way (Hubble)
Huge cloud of cold, thinly dispersed interstellar gas and dust (mostly H & He) Hubble image at http://hubblesite.org/newscenter/archive/releases/nebula/emission/2006/41/image/a/
How Did We Get a Solar System?
Image: LPI Concentrations of dust and gas in the cloud; material starts to collect (gravity > magnetic forces) Hubble image at http://hubblesite.org/newscenter/archive/releases/nebula/emission/2005/35/image/a/
How Did We Get a Solar System?
Gravity concentrates most stuff near center Heat and pressure increase Collapses – central proto-sun rotates faster (probably got initial rotation from the cloud) Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_1.html
How Did We Get a Solar System?
• Rotating, flattening, contracting disk - solar nebula! Equatorial Plane Orbit Direction NASA artwork at http://en.wikipedia.org/wiki/Image:Ra4-protoplanetary-disk.jpg
How Did We Get a Solar System?
• After ~10 million years, material in center of nebula hot enough to fuse Hydrogen (H) • “...here comes the Sun…” NASA/JPL-Caltech Image at http://www.nasa.gov/vision/universe/starsgalaxies/spitzer-20060724.html
How Did We Get a Solar System?
• Metallic elements (Mg, Si, Fe) condense into solids at high temps. Combined with Oxygen to make tiny grains • Lower temp (H, He, CH4, H2O, N2, ice) - outer edges Planetary Compositions Hubble photo at http://hubblesite.org/newscenter/archive/releases/star/protoplanetary-disk/2005/10/image/a/layout/thumb/
How Did We Get a Solar System?
Inner Planets: • Hot – Silicate minerals, metals, no light elements, ice • Begin to stick together with dust clumps Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_3.html
How Did We Get a Solar System?
Outer Solar System • Cold – ices, gases – 10x more particles than inner • May have formed icy center, then captured lighter gases (Jupiter and Saturn first? Took H and He?) • Leave C,O, and N for the others Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_5.html
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Terrestrial planets
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Heavier elements stable at higher temperature Condensed in inner nebula
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Gas giants
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Lighter elements (H, He, C, O, N) stable at lower temperature
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Condensed in outer nebula
Where do Comets Originate?
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Orbital paths of comets
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Highly elliptical (oval-shaped) 1 complete orbit is called a period Short-period comets
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Revolve around the Sun less than 200 yrs E.g. Comet Halley Paths are close to the same plane of orbit as planets
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Orbit is the same direction as the Sun Originate from the Kuiper belt
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Long-period comets
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Longer than 200 years to go around once Orbital path is random
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Direction and plane of orbit
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E.g. Comet Hale-Bopp Originated in Oort cloud
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Spherical cloud, 20 trillion miles beyond the Sun
How Did We Get a Solar System?
• Accretion - particles collide and stick together … or break apart … gravity not involved if small pieces • Form planetesimals, up to a few km across Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_3.html
How Did We Get a Solar System?
• Gravitational accretion: planetesimals attract stuff • Large protoplanets dominate, grow rapidly, clean up area ( takes ~10 to 25 My) Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_4.html
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Smaller protoplanets (inner solar nebula)
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Unable to accrete gas because of their higher temperature
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Obtain their atmospheres from the impact of comets Largest protoplanets (outer solar nebula)
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Accrete gas because of their cooler temperature
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Strongly influence the orbits of the remaining comets
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Either send them out to the Oort cloud or Send them inward where they collide with the terrestrial planets
How Did We Get a Solar System?
The Asteroid Belt ? Should have been a planet instead of a debris belt? Jupiter kept it from forming Eros image at http://solarsystem.nasa.gov/multimedia/gallery.cfm?Category=Planets&Object=Asteroids&Page=1
How Did We Get a Solar System?
Beyond the Gas Giants - Pluto, Charon and the Kuiper Belt objects Chunks of ice and rock material Little time / debris available to make a planet – slower!!
Taken from Hubble Telescope Charon is Pluto’s moon, only a Little smaller than Pluto Pluto’s surface temp. is as low as -400
°
F From the surface of Pluto, the Sun looks like a very bright star
Early in the Life of Planets
• Planetesimals swept up debris • Accretion + Impacts = HEAT • Eventually begin to melt materials • Iron, silica melt at different temperatures • Iron sank – density layering Image from LPI: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=168
Mercury
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Average density of 5430 kg/m 3
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Second highest density of all planets
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Like Earth, has an Iron core
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2/3 to ¾ of the radius of the planet!
Iron-Nickel core
Venus
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Composition ~ to Earth Crust 10-30 km thick Mantle Core – Iron-Nickel Average density is 5240 kg/m 3
Earth
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Crust, mantle, and core Crust
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~ 30 km thick for land (granite) ~ 5 km for oceanic crust (basalt) Mantle Core, Iron-Nickel
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Liquid outer core Inner solid core Average density ~ 5520 kg/m 3
Mars
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~ ½ the diameter of Earth Crust Mantle Core ,
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Iron-Nickel and Iron sulfide Density ~ 3930 kg/m 3
Pluto
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Structure not very well understood Surface is covered with methane ice Surface temp ~ 400
°
F Frozen methane shows a bright coloration Density ~ 2060 kg/m 3
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This low of a density suggests that the planet must be a mix of rock and ice