theme 10 – leftovers: meteors and asteroids astr 101 prof. dave hanes
TRANSCRIPT
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Theme 10 – Leftovers: Meteors and Asteroids
ASTR 101Prof. Dave Hanes
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Meteors: Individual, or in Groups- not “falling stars!”
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To Be Precise
Meteoroid = the pebble out in space
Meteor = the luminous event we see (the trail of the “falling star”)
Meteorite = any surviving lump that we find on the ground
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What We Are Seeing
Most meteors are small (tiny pebbles, or even grains, of rocky material)
They enter Earth’s atmosphere at very high speed (many tens of km/sec)
Air resistance slows them and heats both the pebble and the column of air – this is what we see, not the pebble itself
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Some Can be Very Bright
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A Range of Sizes
(‘Pebbles’ burn up!)
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Ahnigito (“The Tent”) Meteorite
31 tonnes; fell ~ 10,000 years ago
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Duck!
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Finding Them on the Ground
Various types:
stony (undistinguished!)
carbonaceous chondrites,
iron (very distinctive!), …
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Meteor Showers
Not all meteors come in singly.
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Remants of Evaporated Comets
A comet breaks up The rubble gets spread out
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Moving ‘Gravel Pits’- and a trick of perspective
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The Shower has a‘Radiant’ - hence the name (e.g. the Perseids, in
August)
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The Leonids in1833 and 2001
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Asteroids
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We Can Visit Them(Vesta and Ceres)
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Finding New Ones
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‘Earth-Crossing’ Orbits
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We Do Get Hit![here, about 30,000 years ago]
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The Speed is the Key Factor
All of the kinetic energy (the energy of motion) is released when the moving object hits the target.
A 1-gram pebble moving 100 km/sechas as much kinetic energy as a10-ton truck moving along the highway at 100 km/hour
http://www.popularmechanics.com/technology/engineering/gonzo/behold-the-900-mph-supersonic-ping-pong-bazooka-15097897
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The Same Basic Physics!http://www.youtube.com/watch?v=Pi-NIeJ26BI
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Local Examples
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Relatively Recently, in Russia
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Very Recently in Chelyabinsk, Russia
Even a ‘miss’ can be quite destructive
http://www.youtube.com/watch?v=dBvotWfR3j4/
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Back to Tunguska
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How aboutbigger still?