Sungrazing Comets

Sungrazing Comets

Matthew Knight

University of Maryland

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

Halley’s Comet

1910 1986

Hale-Bopp (1995)

Hyakutake (1996)

Kohoutek (1973)

Tempel 1 (2005)

SW3 (2006)

What is a sungrazing comet?

• Comets that “graze” the Sun’s 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

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)

Prominent sungrazing comets

Year Comet name/discoverer

372 BC Ephorus/Aristotle

1106 Europe, China, Japan, Korea, Constantinople, Palestine

1843 Great March Comet

1880 Great Southern Comet

1882 Eclipse Comet aka. “Tewfik”

1882 Great September Comet


1945 du Toit

1963 Pereyra

1965 Ikeya-Seki

1970 White-Ortiz-Bolelli

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

The above movie can be downloaded fromhttp://lasco-www.nrl.navy.mil/mvimpg/xmas_c23_shrt_clean.mpg

Other movies can be obtained fromhttp://sohowww.nascom.nasa.gov/bestofsoho/Movies/movies2.html#comets

The above movie can be downloaded fromhttp://lasco-www.nrl.navy.mil/movies/980411_c3_comet.mpg

Other movies can be obtained fromhttp://sohowww.nascom.nasa.gov/bestofsoho/Movies/movies2.html#comets

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

The Great March Comet

(1843)

The Great September Comet (1882)

Ikeya-Seki (1965)

Prominent sungrazing comets

Year Comet name/discoverer

372 BC Ephorus/Aristotle

1106 Europe, China, Japan, Korea, Constantinople, Palestine

1843 Great March Comet


1882 Eclipse Comet aka. “Tewfik”

1882 Great September Comet


1945 du Toit

1963 Pereyra

1965 Ikeya-Seki

1970 White-Ortiz-Bolelli

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 comet’s nucleus– Helps understand how long a comet lives

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

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

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

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/

Sungrazing Comets

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