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Comets

Comets. 30 October 2015. Introduction. The history of comet watching dates back to 1000 BC from the Chinese records and Chaldea, a place in present Iraq. Comets have been regarded as omen, even as recently as 1986. Battle of Hastings – 1066 – Bayeau Tapestry

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Comets

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  1. Comets 30 October 2015

  2. Introduction • The history of comet watching dates back to 1000 BC from the Chinese records and Chaldea, a place in present Iraq. • Comets have been regarded as omen, even as recently as 1986. • Battle of Hastings – 1066 – Bayeau Tapestry • Today Astronomers study Comets from scientific perspectives, and our understanding of these fascinating objects have grown tremendously.

  3. Dirty Snowballs • Comets are dusty chunk of ice • During each orbit around the sun they partially vaporize • Have elliptical Orbits Courtesy: Calvin J. Hamilton

  4. Orbits of Comets • Elliptical in Shape • Randomly oriented Aphelion distance Comet Sun Earth Perihelion distance

  5. Comet Hunters • Comet are named by International Astronomical Union (IAU) after the person who first discovers them. • Many comets are discovered by amateur astronomers. • Charles Messier, E. E. Bernard, Shoemaker and Levy, Hale and Bopp, Ikeya, Seki and Hayakutake are popular comet hunters.

  6. Origins of Comets • Comets are thought to be the left over debris from during the time of formation of the solar system. • The elliptical orbits of comets suggest that they underwent gravitational pull from the giant planets. • This all lead us to infer two possible locations where comets could start their journey towards the sun: Oort Cloud for long period comets; Kuiper Belt for short period.

  7. Comets Tails • Ludwig Biermann propose the idea of solar wind to explain comet tails. Mariner 2 spacecraft captured the one such event in 1962.

  8. Comet Collisions Courtesy: NASA/JPL

  9. Kohoutek

  10. Comet West

  11. Shoemaker-Levy 9

  12. Shoemaker-Levy hits Jupiter

  13. Hale-Bopp Ion tail & Dust tail

  14. Halley from Giotto

  15. Hyakutake

  16. Deep Impact Tempel 1

  17. Comet ISON 4 October 2013

  18. Comet ISON 10 April 2013

  19. Comet ISON 8 October 2013

  20. ISON’s path through the sky

  21. ISON approaches the Sun

  22. ISON is only debris cloud after passing Sun

  23. Comet Hartley jets

  24. Comet McNaught 2007

  25. Siding Spring at Mars October 2014

  26. MER PanCam

  27. MAVEN IUVS Siding Spring

  28. Latest Rosetta Images: Landing, 12 Nov 2014 Perihelion: 13 August 2015

  29. Rosetta Target: 67P C-G

  30. Boulder ‘Cheops’

  31. Approaching Perihelion

  32. Outburst in Action

  33. View through Camera 4

  34. P67 Rotation and Regions

  35. Active Pits

  36. Key Concepts • Kuiper Belt, exterior to Neptune is the primary source of short period (P<200yr) comets • Oort Cloud, 10,000 AU from Sun, reservoir of long period comets, stored there billions of years • Small objects much more abundant • Cometary activity is triggered by sunlight • Comet tails: dust, shaped by solar radiation; ion or plasma tail shaped by solar wind • Comet grains: CHON + refractory matter • Comet nucleus: dirty snowball

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