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Chapter 11, 12,13. Comets, Asteroids, Meteors. Minor Body Comparisons. Property ___Asteroids _________ Comets. Orbit ShapeCircular to Highly elliptical elliptical. Size 0.5 km to 625 kmNucleus 1 to 10 km. - PowerPoint PPT Presentation
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Chapter 11, 12,13Chapter 11, 12,13 Comets, Asteroids, MeteorsComets, Asteroids, Meteors
Minor Body ComparisonsProperty ___Asteroids _________ Comets
Orbit Shape Circular to Highly elliptical elliptical
Size 0.5 km to 625 km Nucleus1 to 10 km
Composition Iron or Rocky Ice and Rock
Named? Named by their Named after theirdiscoverers discoverers
Asteroids• a.k.a Minor Planets
• Belt Asteroids - are those found between the orbits of Mars and Jupiter.
• Trojan Asteroids - share Jupiter's orbit about the Sun
• Apollo Asteroids – have orbits that cross Earth’s orbit
• NEO – Near Earth Objects
Kirkwood Gaps
Asteroids• The are empty regions in the asteroid belt
called Kirkwood Gaps.• (Created by Jupiter’s gravity)
Blink Comparison
Minor Planet
Asteroids• The asteroids are probably fragments of
planetesimals, the bodies from which planets were built.
• Over 100 “new” asteroids are discovered every year.
• There are over 7,000 known asteroids.• Examples:
– Ceres (diameter = 625 miles)
– Gaspra (3 by 12 miles)
– Toutatis (0.5 by 2 miles)
Goldstone Deep Space Communications Complex
Toutatis
• A strange binary asteroid imaged with radar from Earth.
2.5 and 1.6 miles
Gaspra
• The first asteroid to be imaged at close range.
• This was done with the Galileo spacecraft.
12 miles
Ida
• The second asteroid imaged with the Galileo spacecraft.
• It has a moon!
Satellite!
36 x 14 miles
Methilde
• The spacecraft NEAR made a flyby of Mathilde on June 27, 1997.
Vesta
• Vesta has been studied recently with Hubble Space Telescope.
Diameter = 165 miles
Comets• There are two reservoirs for comets
• Kuiper Belt • Oort Cloud
• The solar wind produces two tails on comets: the dust tail and the ion tail.
• Examples: • Halley's Comet• Hale-Bopp• Shoemaker-Levy 9
The Oort Cloud
Structure of a Comet
To Sun
Ion Tail
Dust Tail
Coma
Comet Halley
• It orbits the Sun every 76 years.
• It was imaged in 1986 at close range by Giotto, a European satellite.
Comet Halley 1910
•Pope Callixtus III excommunicated Halley's Comet in 1456
•In 1910, charlatans sold "comet pills"
Comet Nucleus
Hyakutake
Hale-Bopp
Comet West
Comet Shoemaker-Levy 9
Comet Shoemaker-Levy 9
The End.
Comet Shoemaker-Levy 9
• Was shatter by Jupiter’s gravity in 1992.
• All pieces hit Jupiter in the summer of 1994 leaving dark impact scars.
Meteors
• meteoroid - small debris moving though space
• meteorite - space debris found on Earth• Types
• iron meteorites• chondritic meteorites
Iron Meteorites
Chondritic Meteorites
Meteors• Sporadic Meteor
• Random meteors with various compositions
• Bolides• Leave trails (trains) that last for a few minutes
• Sometimes make noise
• Fireball• Sometimes take over half a minute to cross the sky
• Sometimes have magnitudes brighter than Venus
Meteors• How can you determine the composition of
a meteor?• Take its spectra.
• How can you tell how high it vaporizes?• Triangulation from two observers.
Sporadic Meteors
Irons Stony-Irons
Chondrites Carbonaceous Chondrite
Achondrite
Meteors• meteor
• a.k.a. “shooting star”
• A small bit of rock that is heated by friction in the Earth’s atmosphere and gives off light
• meteor shower• Results from the Earth passing though a comet's path
• Can result in 100’s of meteors per minute
• Are named after the radiant constellation
Meteor Shower
The 1833 storm
The Cause of Meteor Showers
P55/Tempel-Tuttle
Earth Impacts and Near Misses
• Arizona Meteor Crater• measures 1 mile across
• from an impact 50,000 years ago
• by a 50 meter meteoroid
• Tunguska Event• in 1908
• an asteroid broke up in our atmosphere
• leveled trees for some 30 kilometers
• Chicxulub Event /cheek-shoo-loob/• 65,000,000 years ago
• 10 kilometer asteroid
• is thought to have caused a mass extinction of dinosaurs
How are asteroids and comets discovered?
• Two pictures are taken of the same region of the sky at different times.
• If any object in the pictures has moved then it could be…
• an asteroid• or comet• or a planet• or a UFO.
How Much Damage?
The End...
Live long and prosper.