1. Update 3/12/2009Modified by C. Ippolito March 2009 Rendezvous with a Comet Courtesy: Pat Rawlings - Deep Impact -NASA & JPL Page 1

2. Update 3/12/2009Modified by C. Ippolito March 2009 Introduction  1000 BC from the Chinese records  Omen, even as recently as 1986.  Battle of Hastings - 1066  Now studied from scientific aspect  1000 BC from the Chinese records  Omen, even as recently as 1986.  Battle of Hastings - 1066  Now studied from scientific aspect Page 2

3. Update 3/12/2009Modified by C. Ippolito March 2009 Dirty Snowballs  as they orbit around the sun they partially vaporize  elliptical orbits  as they orbit around the sun they partially vaporize  elliptical orbits Courtesy: Calvin J. Hamilton Page 3

4. Update 3/12/2009Modified by C. Ippolito March 2009 Structure of a Comet  Solar heat vaporizes  Coma - Hydrogen gas Envelope  Dust tail  Ion tail  Solar heat vaporizes  Coma - Hydrogen gas Envelope  Dust tail  Ion tail Courtesy: Deep Impact - NASA & JPL Page 4

5. Update 3/12/2009Modified by C. Ippolito March 2009 Orbits of Comets  Elliptical in Shape  Randomly oriented  Elliptical in Shape  Randomly oriented Sun Comet Earth Perihelion distance Aphelion distance Page 5

6. Update 3/12/2009Modified by C. Ippolito March 2009 Comet Hunters  Named by International Astronomical Union (IAU)  after discoverer  Often discovered by amateurs.  Charles Messier  E. E. Bernard  Shoemaker and Levy (hit Jupiter)  Hale and Bopp  Named by International Astronomical Union (IAU)  after discoverer  Often discovered by amateurs.  Charles Messier  E. E. Bernard  Shoemaker and Levy (hit Jupiter)  Hale and Bopp Page 6

7. Update 3/12/2009Modified by C. Ippolito March 2009 Origins of Comets  debris from formation of the solar system.  elliptical orbits influenced by gravitational pull of giant planets.  Two possible “home” locations:  Kuiper Belt  Oort Cloud  debris from formation of the solar system.  elliptical orbits influenced by gravitational pull of giant planets.  Two possible “home” locations:  Kuiper Belt  Oort Cloud Page 7

8. Update 3/12/2009Modified by C. Ippolito March 2009 Possible Homes for Comets  Kuiper Belt  Gerard Kuiper 1951)  Elliptic  30 to 500 AU  100,000 objects  Oort Cloud  Jan Oort (1950)  spherical.  50,000 AU from the Sun.  5 trillion objects.  Kuiper Belt  Gerard Kuiper 1951)  Elliptic  30 to 500 AU  100,000 objects  Oort Cloud  Jan Oort (1950)  spherical.  50,000 AU from the Sun.  5 trillion objects. Courtesy - Deep Impact - NASA - JPL Page 8

9. Update 3/12/2009Modified by C. Ippolito March 2009 Comets and their periods  Jupiter-family: Kuiper belt  20 years.  Gravitational perturbations by Neptune  Elliptical orbits close to the Sun  Or Captured by Saturn as outer satellites  Jupiter-family: Kuiper belt  20 years.  Gravitational perturbations by Neptune  Elliptical orbits close to the Sun  Or Captured by Saturn as outer satellites Page 9

10. Update 3/12/2009Modified by C. Ippolito March 2009 Comets Tails  Ludwig Biermann  solar wind causes comet tails.  Mariner 2 (1962.)  Ludwig Biermann  solar wind causes comet tails.  Mariner 2 (1962.) Page 10

11. Update 3/12/2009Modified by C. Ippolito March 2009 Comets Tails  THREE Tails.  Blue Ion Tail  ionized atoms of CN and C 2.  Dust Tail  sun photons hit dust particles  produce radiation pressure.  curved shape.  Sodium Tail  invisible to unaided eyes.  THREE Tails.  Blue Ion Tail  ionized atoms of CN and C 2.  Dust Tail  sun photons hit dust particles  produce radiation pressure.  curved shape.  Sodium Tail  invisible to unaided eyes. Page 11

12. Update 3/12/2009Modified by C. Ippolito March 2009 Comet Collisions  Earth  devastation to life on Earth.  Jupiter  Shoemaker-Levey  taped  important facts about Comet collisions.  Earth  devastation to life on Earth.  Jupiter  Shoemaker-Levey  taped  important facts about Comet collisions. Page 12