Comets

1
Comets

• Small dusty/icy chunk of material few kms size
  (often characterized as dirty snowball)
• Originally condensed out of Solar nebula and
  still orbit Sun - primitive material
• Orbits often elliptical, large aphelion
• Partially vaporized when close to Sun - material
• (gases) then pushed by sunlight makes long
  tail
• Gas tail always points away from Sun
• Also dust tail along orbit

2
COMET IKEYA-SEKI
3
COMET WEST
4
COMET HALE-BOPP
5
PARTS of a COMET
6
COMET TAIL ORIENTATION
7
RECIPE for a COMET

• Ingredients
• Frozen methane
• Frozen water
• Frozen ammonia
• Dust grains (dirt)
• Traces of organic compounds and other chemicals
• Directions
• Mix into a ball about 10 km across containing
  100,000,000,000,000, (1014) kg of this mixture

8
COMET HALLEY
9
COMET HALLEYS ORBIT
10
COMET HALLEYS PATH 1910 and 1986
1910
11
(No Transcript)
12
Returns to Perihelion of Halleys Comet Returns to Perihelion of Halleys Comet Returns to Perihelion of Halleys Comet Returns to Perihelion of Halleys 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
13
BAYEUX TAPESTRY
14
Giotto-Adoration of the Magi
15
ORIGIN of LONG PERIOD COMETS

• Originate in Oort Cloud
• a huge reservoir
• ancient Solar System
• material far from Sun
• likely produced by
• planetesimals ejected
• by Jupiter and Saturn
• Early on from inner
• Solar System.
• Passing star perturbes
• Cloud sends lumps
• inward - see as comets
• when near Sun.

16
KUIPER BELTPlanetesimals ejected from inner
Solar System by stronggravitational 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
17
KUIPER BELT OBJECT
18
KUIPER BELT OBJECTS
Pluto 3 Moons
Sedna e 0.86 Perihelion 76 AU Aphelion 975 AU! P
12,000 years
19
METEORS AND METEORITES

• Meteors are parts of comets that pass through
  Earths orbit - burn up in Earths atmosphere
• Meteorites are ground up pieces of asteroids -
  off orbit - enter Earths atmosphere and survive
  passage

20
Meteor Shower

• Comet breakup
• near perihelion
• Material spread out
• along orbit
• If Earth passes
• through comet debris
• - shower

21
A METEOR STORM
Leonid Shower
1833 Wood Cut
22
LEONID METEOR SHOWERLong Exposure
23
Dates Some Meteor Showers
24
ANTARCTIC METEORITE
Easiest to find meteorites against snow. Most
found in Arctic or Antarctic Primitive material
- planetesimals - useful for dating Solar
System Many varieties - stony, metallic, often
contain organic material