CometsCometsCometsComets Small dusty/icy chunk of material few kms Small dusty/icy chunk of material few kms size (often characterized as “dirty size (often characterized as “dirty snowball”)snowball”)

Originally condensed out of Solar nebula Originally condensed out of Solar nebula and still orbit Sun - primitive materialand still orbit Sun - primitive material

Orbits often elliptical, large aphelionOrbits often elliptical, large aphelion Partially vaporized when close to Sun - Partially vaporized when close to Sun - materialmaterial

(gases) then pushed by sunlight makes long (gases) then pushed by sunlight makes long tailtail

Gas tail always points away from SunGas tail always points away from Sun Also dust tail along orbitAlso dust tail along orbit

COMET IKEYA-SEKICOMET IKEYA-SEKICOMET IKEYA-SEKICOMET IKEYA-SEKI

COMET WESTCOMET WESTCOMET WESTCOMET WEST

COMET HALE-BOPPCOMET HALE-BOPPCOMET HALE-BOPPCOMET HALE-BOPP

PARTS of a COMETPARTS of a COMETPARTS of a COMETPARTS of a COMET

Pushed by SunPushed by Sun

Dust along Dust along comet’s orbitcomet’s orbit

COMET TAIL ORIENTATIONCOMET TAIL ORIENTATIONCOMET TAIL ORIENTATIONCOMET TAIL ORIENTATION

Ion trail

Dust trail

Comet Hale-bopComet Hale-bop

Dust trail

Ion trail

RECIPE for a COMETRECIPE for a COMETRECIPE for a COMETRECIPE for a COMET

IngredientsIngredientsFrozen methaneFrozen methaneFrozen waterFrozen waterFrozen ammoniaFrozen ammoniaDust grains (dirt)Dust grains (dirt)Traces of organic compounds and other Traces of organic compounds and other

chemicalschemicals DirectionsDirections

Mix into a ball about 10 km across containing Mix into a ball about 10 km across containing 100,000,000,000,000, (10100,000,000,000,000, (101414) kg of this mixture) kg of this mixture

About the About the mass of Mt. mass of Mt. BakerBaker

COMET HALLEYCOMET HALLEYCOMET HALLEYCOMET HALLEY

COMET HALLEY’S ORBITCOMET HALLEY’S ORBITCOMET HALLEY’S ORBITCOMET HALLEY’S ORBIT

COMET HALLEY’S PATH COMET HALLEY’S PATH 1910 and 19861910 and 1986

COMET HALLEY’S PATH COMET HALLEY’S PATH 1910 and 19861910 and 1986

1910 1986

Returns to Perihelion of Halley’s Comet

239 BC March 30 989 September 9

163 BC October 5 1066 March 23

86 BC August 2 1145 April 22

11 BC October 5 1222 October 1

AD 66 January 26 1301 October 23

141 March 20 1378 November 9

218 May 11 1456 June 9

295 April 20 1531 August 25

274 February 16 1607 October 27

451 June 24 1682 September 15

530 September 25 1759 March 13

760 May 22 1835 November 16

837 February 27 1910 April 20

912 July 9 1986 February

BAYEUX TAPESTRYBAYEUX TAPESTRYBAYEUX TAPESTRYBAYEUX TAPESTRY

Giotto-Adoration of the MagiGiotto-Adoration of the MagiGiotto-Adoration of the MagiGiotto-Adoration of the Magi

ORIGIN of LONG PERIOD ORIGIN of LONG PERIOD COMETSCOMETS

ORIGIN of LONG PERIOD ORIGIN of LONG PERIOD COMETSCOMETS

Originate in Oort CloudOriginate in Oort Cloud-a huge reservoir a huge reservoir ancient Solar Systemancient Solar Systemmaterial far from Sunmaterial far from Sun-likely produced by likely produced by planetesimals ejectedplanetesimals ejectedby Jupiter and Saturnby Jupiter and SaturnEarly on from inner Early on from inner Solar System.Solar System.

Passing star perturbesPassing star perturbesCloud sends lumpsCloud sends lumpsinward - see as cometsinward - see as cometswhen near Sun.when near Sun.

KUIPER BELTPlanetesimals ejected from inner Solar System by strong

gravitational fields of Giant Planets - some interact Jupiter and Saturn flung far out to Oort Cloud, interactions Uranus and

Neptune pushed them out to Kuiper Belt

KUIPER BELTPlanetesimals ejected from inner Solar System by strong

gravitational fields of Giant Planets - some interact Jupiter and Saturn flung far out to Oort Cloud, interactions Uranus and

Neptune pushed them out to Kuiper Belt

Kuiper Belt

KUIPER BELT OBJECTKUIPER BELT OBJECTKUIPER BELT OBJECTKUIPER BELT OBJECT

KUIPER BELT OBJECTSKUIPER BELT OBJECTSKUIPER BELT OBJECTSKUIPER BELT OBJECTSSedna e =0.86Perihelion 76 AUAphelion 975 AU!P =12,000 years

Pluto + 3 Moons

METEORS AND METEORS AND METEORITESMETEORITES

METEORS AND METEORS AND METEORITESMETEORITES

Meteors are parts of Meteors are parts of comets that pass through comets that pass through Earth’s orbit - burn up Earth’s orbit - burn up in Earth’s atmospherein Earth’s atmosphere

Meteorites are ground up Meteorites are ground up pieces of asteroids - off pieces of asteroids - off

orbit - enter Earth’s orbit - enter Earth’s atmosphere and survive atmosphere and survive

passagepassage

Meteor ShowerMeteor ShowerMeteor ShowerMeteor Shower

Comet breakupComet breakupnear perihelionnear perihelion

Material spread outMaterial spread outalong orbitalong orbit

If Earth passesIf Earth passesthrough comet debristhrough comet debris- shower- shower

A METEOR STORMA METEOR STORMA METEOR STORMA METEOR STORM

1833 Wood Cut

Leonid Shower

LEONID METEOR SHOWERLEONID METEOR SHOWERLong ExposureLong Exposure

LEONID METEOR SHOWERLEONID METEOR SHOWERLong ExposureLong Exposure

Dates Some Meteor ShowersDates Some Meteor ShowersDates Some Meteor ShowersDates Some Meteor Showers

ANTARCTIC METEORITEANTARCTIC METEORITEANTARCTIC METEORITEANTARCTIC METEORITE

Easiest to find meteoritesagainst snow.

Most found in Arctic orAntarctic

Primitive material - planetesimals - useful fordating Solar System

Many varieties - stony,metallic, often containorganic material