asteroidsifa.hawaii.edu/~howard/ast241/asteroids.pdf · 2014-10-28 · giant asteroids vesta...
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Astronomy 241: Foundations of Astrophysics I
18. Asteroids
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100 AU
5 AU
S
20,000 AU
Overview: Structure
Inner system: terrestrial planets, asteroids.
Outer system: giant planets and moons, “KBOs”.
Oort Cloud: comets.
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Asteroids and comets to scale
Comet Nuclei
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Samples From the Asteroid Belt
Primitive meteorites are relics of the solar system’s formation, 4.6 Gyr old.
Processed meteorites come from differentiated asteroids, later broken up by collisions.
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Element Abundances
The Solar System
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Eros
a = 1.5AU, e = 0.22 34 x 11 x 11 km S-‐type Density = 2700 kg m-‐3
Prot = 5 hr Disc. 1898 (Carl WiI) V ~ 8.1 mag (binoculars) Visited by NEAR-‐Shoemaker probe
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The Last Global Rotation Movie
Mission to Eros
Eros: The Final Approach
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Asteroid Light Curves
An Asteroid Rotation Factory
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Diameter vs Rotation Rate
Some asteroids are rubble piles: loose collections of fragmented rock held together by self-gravity.
Spin Limits of Solar System Bodies
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Diameter vs Rotation Rate
Some small asteroids rotate so fast that they must be monoliths held together by material strength.
Spin Limits of Solar System Bodies
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PIA15678: Full View of Vesta
Giant Asteroids
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Giant Asteroids
Vesta
Largest Asteroid May Be 'Mini Planet'
Ceres975 km
Large asteroids are complex objects which appear to have differentiated.
530 km
PIA14321: Vesta Full Rotation Movie PIA15510: Vesta's Internal Structure
Basaltic crust
Mantle
Iron-Nickel core
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Wikipedia: Asteroid belt
Jupiter
Hildas
Trojans
Trojans
Mars
Belt Structure 14 August 2006
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Jupiter
Hildas
Mars
Trojan Asteroids
L4
L5
Wikipedia: Asteroid belt
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Orbits starting near L4
ma/mb = 49
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Orbits starting near L1
ma/mb = 49
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Wikipedia: Hilda family
Hilda Asteroids
2:3 MMR; stable since they avoid Jupiter (e ~ 0.3).
Small inclinations (i ≲ 20°).Wikipedia: Hilda family
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Asteroid Belt Populations
Asteroid Families
Many asteroids are members of families; they have similar orbits and compositions (indicated by colors).
Inner belt asteroids (left) and families (right).
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Suspected Asteroid Collision Leaves Odd X-Pattern of Trailing Debris
A Suspected Asteroid Collision