Transcript How Did We Get a Solar System?

Formation of Our Solar System
Modified presentation originally created by the Lunar and Planetary
Institute
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 (counterclockwise viewed from above)
Lunar and Planetary Institute image at
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=175
Some more data to explain:
4. Most planets rotate in this same direction
Mercury 0°
Jupiter 3°
Venus 177°
Saturn 27°
Earth 23°
Mars 25°
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
Huge cloud of cold, thinly dispersed
interstellar gas and dust – threaded
with magnetic fields that resist
collapse
Hubble image at
http://hubblesite.org/newscenter/archive/releases/nebula/emission/2006/41/image/a/
How Did We Get a Solar System?
Image: LPI
The cool nebular gas contained about five hydrogen
molecules for every helium atom (H - 71%, He - 27%
by mass). The temperature in the outer solar system
was cold enough for H2 molecules to form.
How Did We Get a Solar System?
Image: LPI
Other elements C, N, O bond with H to form CH4, NH3
and H2O. Astronomers call these “ices” because they
can condense into solids in a cold nebula. There may
have also been small amounts of CO and CO2. About
0.5% of the nebula was metal and silicate rock.
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 protosun 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 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
O 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?
• 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
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?)
Image: LPI http://www.lpi.usra.edu/education/timeline/gallery/slide_5.html
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!!
How Did We Get a Solar System?
Comets
• Dirty snowballs - small objects of ice, gas, dust,
tiny traces of organic material
Image from: http://antwrp.gsfc.nasa.gov/apod/ap000805.html
Early in the Life of Planets
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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
When did Our Solar System Form …
How do We Know?
Image: Lunar and Planetary Laboratory:
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=178
When Did the Solar System Form?
• 4.56 billion years ago
• How do we know? (evidence for formation)
•Lunar samples - 4.5 to 4.6 Ga
•Meteorites - 4.56 Ga
•Earth – 3.9 (or 4.4 Ga)
Lunar meteorite at
http://meteorites.wustl.edu/lunar/stones/mac88105.htm
Meteorite photo by Carl Allen at
http://ares.jsc.nasa.gov/Education/Activities/ExpMetMys/..%5C..%5CSlideSets/ExpMetMys/Slides1-9.htm
How Do We Know
How Our Solar System Formed?
Solar System
Samples
Meteorites
Image: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=2093
And http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-asteroids.html
We Can Also Look Around ….
Close-up of "Proplyds" in
Orion
Thanks Hubble!
Hubble images at
http://hubblesite.org/newscenter/archive/releases/nebula/emission/1994/24/image/a/ and
http://hubblesite.org/newscenter/archive/releases/nebula/emission/1994/24/image/b/
We Can Also Look Around ….
This dusty disc around a
newly formed star has a gap,
thought to have been carved
by newly forming gas giant
planets clearing out their
orbits as they circle the star.
ALMA images at
http://www.almaobservatory.org/en/visuals/images/main.php?g2_itemId=3991 and
http://www.almaobservatory.org/en/visuals/images/main.php?g2_itemId=3984
artist’s impression
We Can Also Look Around ….
artist’s impression
This shows a dust trap in the disc that
surrounds the system Oph-IRS 48.
The dust trap allows tiny dust
particles to clump together and grow
to larger sizes. The green area is the
dust trap, where the bigger particles
accumulate.
ALMA images at
http://www.almaobservatory.org/en/visuals/images/main.php?g2_itemId=4974 and
http://www.almaobservatory.org/en/visuals/images/main.php?g2_itemId=3984