Sungrazing Comets

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Sungrazing Comets
(or How you can find comets without being a
professional astronomer)

• Matthew Knight
• University of Maryland

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Halleys Comet
1910
1986
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Hale-Bopp (1995)
Hyakutake (1996)
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Kohoutek (1973)
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Tempel 1 (2005)
SW3 (2006)
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What is a sungrazing comet?

• Comets that graze the Suns surface
• Orbits pass within a few solar radii of the Sun
• Typically only seen close to the Sun, when they
  get very bright
• Allows much smaller comets to be seen
• Most are part of a family which all fragmented
  from a single parent comet
• Comets spread out in a chain along the orbit
• Have similar shaped orbits
• Arrive at the Sun at slightly different times

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History of sungrazer discoveries

• Ground based discoveries (10-15)
• None since 1970
• Space based
• Solwind 1979-1985 (10)
• Solar Maximum Mission 1980-1989 (10)
• SOHO 1996-present (1137)

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Prominent sungrazing comets
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Sungrazing comets discovered by SOHO

• Kreutz (948)
• Marsden (30)
• Meyer (70)
• Kracht (28)
• Kracht II (3)
• No family (51)

Statistics as of 5/20/06
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The above movie can be downloaded
from http//lasco-www.nrl.navy.mil/mvimpg/xmas_c23
_shrt_clean.mpg Other movies can be obtained
from http//sohowww.nascom.nasa.gov/bestofsoho/Mov
ies/movies2.htmlcomets
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The above movie can be downloaded
from http//lasco-www.nrl.navy.mil/movies/980411_c
3_comet.mpg Other movies can be obtained
from http//sohowww.nascom.nasa.gov/bestofsoho/Mov
ies/movies2.htmlcomets
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Kreutz group

• Period 800 years
• Highly inclined 143º
• Pass the closest to the Sun
• Demonstrate the effects of higher temperatures
  and gravity than anything else in the Solar
  System
• Famous members
• C/1843 D1 The Great March Comet
• C/1882 R1 The Great September Comet
• C/1965 S1 Ikeya-Seki

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The Great March Comet (1843)
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The Great September Comet (1882)
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Ikeya-Seki (1965)
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Prominent sungrazing comets
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Prominent sungrazing comets
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Marsden Kracht groups

• Period 5 years
• Related to
• Comet 96P/Machholz
• Quadrantid (January) and Arietid (May-July)
  meteor shower
• Repeat observation allows measurement of erosion
  of comets nucleus
• Helps understand how long a comet lives

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Other sungrazing comets

• Meyer group
• Very high inclination (72º)
• Kracht II group
• Predicted to have a period of 4 years
• Next return in August 2006
• Non-group comets
• Possibly more groups could be found

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Comet discoveries in the future

• SOHO will soon be replaced by STEREO
• Scheduled to launch in summer 2006
• Two space-based coronagraphs which look at the
  Sun in stereo
• Will have a much larger field of view and will be
  sensitive to fainter comets
• Much better orbit determination than SOHO

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Comet discoveries in the future

• Next generation of surveys
• Pan-STARRS
• Four 1.8-m telescopes in Hawaii
• Large Synoptic Survey Telescope (LSST)
• 8.4-m telescope in Chile
• Discovery Channel Telescope (DCT)
• 4.2-m telescope at Lowell Observatory, AZ

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Want to get involved?

• You can search for sungrazing comets using
  publicly available data from SOHO
• http//ares.nrl.navy.mil/sungrazer/
• http//groups.yahoo.com/group/sohohunter/
• http//www.sungrazer.org/