meteors, meteorites, and meteor showers. meteor terminology meteoroids - interplanetary debris...
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Meteors, Meteorites, and Meteor Showers
Meteor TerminologyMeteoroids - interplanetary debris
Meteor - Also called “shooting star”
When a meteorite has entered the
atmosphere creating a streak of light
Meteorite - Those few meteoroids that make
it to the Earth’s surface
Types of Meteorites
• Mostly made of iron with about 9% nickel
IRONS:
STONES:• Primarily silicates
similar to Earth rocks
STONY-IRONS:• Mixture of the above
two types
Meteor Showers
• Associated with debris left behind by comets
• Typically very small meteoroids, so no meteorites are produced during a shower
• Can be as many as 100 meteors per hour in a good shower
Major Meteor Showers
• Often named for the constellation they fall from
Name When # per hour Constellation
Quadrantids Jan. 30-40 Bootes
Perseids Aug. 50-70 Perseus
Leonids Nov. 50-70 Leo
Geminids Dec. 40-50 (multi-colored) Gemini
Meteor Impacts• One catastrophic meteor impact every 26
million years• Might have been responsible for dinosaur
extinction
Barringer crater in Arizona (1200 m in diameter, 200 m deep)
Comets
Comet West
Comet Basics• Comets are mostly (~50%) water ice
• Comets are referred to as “dirty snowballs”
• They are a mixture of water ice, frozen gases, and silicate materials
• Comets have very eccentric orbits
• They only have tails when close to the Sun
• The tails are made of gas and dust released by the comet.
Anatomy of a Comet
Dust Tail
Ion TailComaDirection
of Comet’s Motion
To Sun
Nucleus
Hydrogen Cloud
Comet Halley
• Orbits Sun every 76 years
• Furthest point in its orbit is just beyond the orbit of Neptune
• Nucleus: 15 x 8 x 8 km• Rotates every 7.6 days
Recent Comets
Comet Hyakutake in March of 1996
Image taken by J. De Buizer and J. Radomski of the University of Florida Department of Astronomy
Recent Comets
Comet Hale-Bopp in March 1997
Image taken by J. DeBuizer and J.Radomski of the University of Florida Department of Astronomy
Small Bodies of the Solar System
Pluto, Comets, Asteroids,
Meteors and Zodiacal Light
PLUTOGod of the Underworld
Pluto Physical Data
• Discovered by Clyde W. Tombaugh in 1930
• Diameter: 2294 km (0.18 Dearth)
• Mass: 1.2x1025 g (0.002 Mearth)
• Density: 1.84 g/cm3
• Rotation Period: 6.39 days
• Tilt of Axis: 96o (retrograde!)
• Surface Temperature: 43 K (-382o F)
Pluto Physical Data
• Orbital Semi-Major Axis: 39.44 AU
• Orbital Period: 247.7 years
• Orbital Inclination: 17.2o
• Orbital Eccentricity: 0.250
• Surface Gravity: 0.06 Earth gravity
• Satellites: 1
• Magnetic Field: unknown
The Discovery of Planet X
• Discovered Feb 8, 1930 by then 24-year old Clyde Tombaugh
• Its existence was predicted by Percival Lowell using the same techniques that Leverrier used to find Neptune
The Discovery of Planet X
The Plates on which Clyde Tombaugh found Pluto
January 23, 1930 January 29, 1930
Pluto’s Surface• This image was taken
by the Hubble Space Telescope and is the best surface map yet made
• Only contrasts are seen, no features
• Pluto has not yet been visited by spacecraft
Pluto’s Atmosphere
• Very thin atmosphere (when closest to Sun)
• Envelopes its moon too
• Mostly made of Nitrogen and Methane
• Atmosphere condenses and snows to the surface of Pluto and its moon when they are farther from the Sun
Pluto’s Moon
CHARON:• Discovered by James
Christy in 1978• Saw a bump move from
one side of Pluto to the other about every six days
• About half the size of Pluto, orbits retrograde
One of Christy’s images
Pluto’s Moon
• As seen by Hubble Space Telescope
19,700 km
Pluto
Charon
Pluto’s Strange Orbit
• Pluto’s Orbit is highly eccentric (0.250), highly inclined to the plane of the solar system (17.2o), and its orbit crosses Neptune’s!
• Since Jan 23, 1979 and until March 15,1999 Pluto is closer to the Sun the Neptune!
Pluto’s Orgin
• Since Pluto and Charon are thought to have the same composition as Neptune’s Triton, it is suggested that they might be escaped satellites of Neptune (dynamicists say no)
• Or Triton, Pluto and Charon all formed near Neptune and only Triton was captured
Asteroids
The Asteroid BeltTheory 1:• Material between Jupiter and Mars tried to form a
planet when the Solar System was forming, but Jupiter’s gravitational influence wouldn’t let it happen
Theory 2:• A planet did form between Jupiter and Mars
(Asteroidia), and some catastrophic event destroyed the planet, leaving the asteroids
The Discovery of Asteroids
• On the first day of the 19th C. (Jan 1,1801), Ceres (the largest known asteroid) was discovered by Giuseppe Piazzi
• By the end of the 19th C., several hundred were known
• We now know of more than 7000
Particular AsteroidsCERES:• The largest asteroid by far• Diameter : 914 km• Contains 25% of the mass of all the asteroids combined
The next largest are Pallas, Vesta, and Hygiea which are between 400 and 525 km in diameter
All other known asteroids are less than 340 km across
Particular Asteroids
• Ida was encountered by the Galileo spacecraft in 1993
• Ida was found to have a small satellite, Dactyl
• Dactyl’s size is 1.6 x 1.2 km, and orbits 90 km above Ida
IIDA and DACTYL:
History of Comets
m
Zodiacal Light and Gegenschein
• Zodiacal light is due to dust, concentrated in the plane of the solar system, that reflects the light of the Sun towards our eyes
• Reflection from the dust also causes a patch of light directly opposite the Sun, called the gegenschein
Ecliptic
Sun
Horizon
ZodiacalLight