5th SECCHI Consortium Meeting
Orsay, France
SECCHI Observations of Comets
and Minor Planets
Karl Battams (NRL)
Overview
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SOHO Recap
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Current comet status
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Comet highlight
SECCHI – Early Results
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HI-2, HI-1 and COR-2
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The COR-2 Kreutz comet problem...
Prospects For SECCHI Comets
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Science discovery potential
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New object discovery potential
Some Highlights For This Coming Year
SOHO – History's Greatest Comet
Discoverer!
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To date, SOHO has discovered
1,273 previously unknown
comets
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1,069 Kreutz
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30 Marsden
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29 Kracht
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73 Meyer
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72 Non-group (including 3 “Kracht II”;
several “pairs”)
SOHO has discovered three
well-populated comet groups
SOHO Observations of Known Objects
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Comets
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Over a dozen comets
(Machholz (twice), KudoFujikawa, NEAT, Bradfield,
McNaught, ASAS...)
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Asteroids
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Ceres and Vesta
Pleasant surprises
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Several of Jupiter's
moons!
Some SOHO Comet Highlights
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Nearly 1,300 new discoveries!!
Link between comet Machholz and the Marsden and
Kracht groups (and two meteor showers... and an
asteroid...)
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“Clusters” of comets just hours apart
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Wealth of information on the dynamics and evolution of old
comets
Information regarding pre-perihelion fragmentation of comets
CME striking the tail of comet NEAT
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Information on solar wind, comet dust tails and CME-comet
interactions
SECCHI – Early Results:
HI-2 Observations
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Stars
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Apparent limiting magnitude:
~m11
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Too many stars!
Comets and Minor Planets:
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Comet C/2006 M4 (SWAN)
(m9.6)
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Tail of comet C/2006 P1
(McNaught)
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And later, all of it!
Asteroid 15 Eunomia (m10.1)
SECCHI – Early Results:
HI-2 Observations
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Other Objects:
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M31 (Andromeda)
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M16, M17, M22,
M25, M28...
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Milky Way
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LMC, SMC
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Many more!
SECCHI – Early Results:
HI-1 Observations
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Stars:
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Apparent limiting
magnitude: almost
m14?
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m12 stars certainly
visible
Image courtesy of A.Watson, SOHO comet hunter (Australia) using
“Starry Night” software
SECCHI – Early Results:
HI-1 Observations
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Minor Planets:
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(15) Eunomia
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(10) Hygiea
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(532) Herculina
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(8) Flora
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(1) Ceres
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(29) Amphitrite
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(349) Dembowska
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(6) Hebe
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(14) Irene
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(95) Arethusa (m13.3!)
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(219) Thusnelda
And that's just in the HI-1
A data!
SECCHI – Early Results:
HI-1 Observations
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Comets:
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C/2006 M4 (SWAN) at m9.6
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Spectacular C/2006 P1
(McNaught) at m-5.5!
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High-resolution images of dust
tail and striae
Five SOHO-discovered Kreutzgroup comets
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Visible prior to their LASCO
C3 appearance!
HI-1 more sensitive than
LASCO C3
SECCHI – Early Results:
COR-2 Observations
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Apparent limiting magnitude: at
least m11
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Lots of stars
Observed comets:
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Surprisingly few!
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Over 40 “SOHO” Kreutz have
passed through COR-2
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We have seen just four of them
What's the problem?
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Exposure times? Bandpass?
Polarization?
SECCHI – Early Results:
COR-2 Observations
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SECCHI: A salt-free diet?
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Kreutz comets show up well in the sodium-D
line (589.0nm, 589.6nm)
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LASCO C3 (Clear) bandpass: 400-900nm
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LASCO C2 (Orange) bandpass: 520-640nm
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SECCHI COR-2 bandpass: 650-750nm
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SECCHI HI-1 bandpass: 630-730nm
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Sodium-D not visible in COR-2 or HI-1!
But...
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HI-1 is more sensitive to Kreutz than LASCO C3
SECCHI – Early Results:
COR-2 Observations
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So why so few COR-2 Kreutz comets?
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Polarized images?
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Exposure time?
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Kreutz still show in LASCO C2 polarized images, though
are noticeably fainter
LASCO C2 exposures are quadrupled for polarized C2
images (to 100 secs)
Answer:
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Probably both (but I think longer exposures would
really help...)
Scientific Potential
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Discoveries of new comet populations would add to
what is known from SOHO of the end life of a comet
HI observations of “SOHO” comets will extend light
curves to much greater distances
Greatly improved orbit determinations
Detailed images of comet tails (e.g. McNaught) lead to
better understanding of solar wind / comet interaction
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Possible CME-comet interactions
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First 3-D reconstruction of comets
SECCHI Object Discovery
Prospects
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HI-2
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Discoveries extremely infrequent
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HI-1
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Discoveries very likely and relatively frequent
COR-2
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Other surveys have it covered
Could still surprise us...
COR-1
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Very unlikely to make new discoveries due to
limited field of view
Some Highlights For This Year...
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Comet 2P/Encke
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Comet 96P/Machholz
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Mag 6, will pass from HI-1A into HI-1B (also LASCO
C3) (late April)
Mag 8 (very approx), LASCO C3 (faint) and HI-1B
(early April)
C/1999 R1 = C/2002 R5 (SOHO)
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Predicted 3rd perihelion passage (~September)
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Mag 6; LASCO C2, C3 and (hopefully) HI-1B
Many more asteroids...