5th SECCHI Consortium MeetingOrsay, France

SECCHI Observations of Comets and Minor Planets

Karl Battams (NRL)

Overview

● SOHO Recap Current comet status

Comet highlight

● SECCHI – Early Results HI-2, HI-1 and COR-2

The COR-2 Kreutz comet problem...

● Prospects For SECCHI Comets Science discovery potential

New object discovery potential

● Some Highlights For This Coming Year

SOHO – History's Greatest Comet Discoverer!

● To date, SOHO has discovered 1,273 previously unknown comets

1,069 Kreutz

30 Marsden

29 Kracht

73 Meyer

72 Non-group (including 3 “Kracht II”; several “pairs”)

● SOHO has discovered three well-populated comet groups

SOHO Observations of Known Objects

● Asteroids Ceres and Vesta

● Pleasant surprises Several of Jupiter's

moons!

● Comets Over a dozen comets

(Machholz (twice), Kudo-Fujikawa, NEAT, Bradfield, McNaught, ASAS...)

Some SOHO Comet Highlights

● Nearly 1,300 new discoveries!!● Link between comet Machholz and the Marsden

and Kracht groups (and two meteor showers... and an asteroid...) Wealth of information on the dynamics and evolution

of old comets

● “Clusters” of comets just hours apart Information regarding pre-perihelion fragmentation of

comets

● CME striking the tail of comet NEAT Information on solar wind, comet dust tails and CME-

comet interactions

SECCHI – Early Results:HI-2 Observations

● Stars Apparent limiting

magnitude: ~m11● Too many stars!

● Comets and Minor Planets: Comet C/2006 M4 (SWAN)

(m9.6) Tail of comet C/2006 P1

(McNaught)● And later, all of it!

Asteroid 15 Eunomia (m10.1)

SECCHI – Early Results:HI-2 Observations

● Other Objects: M31

(Andromeda)

M16, M17, M22, M25, M28...

Milky Way

LMC, SMC

Many more!

SECCHI – Early Results:HI-1 Observations

● Stars: Apparent limiting

magnitude: almost m14?

m12 stars certainly visible

Image courtesy of A.Watson, SOHO comet hunter (Australia) using “Starry Night” software

● Minor Planets:

(15) Eunomia

(10) Hygiea

(532) Herculina

(8) Flora

(1) Ceres

(29) Amphitrite

(349) Dembowska

(6) Hebe

(14) Irene

(95) Arethusa (m13.3!)

(219) Thusnelda

● And that's just in the HI-1 A data!

SECCHI – Early Results:HI-1 Observations

● Comets: C/2006 M4 (SWAN) at m9.6

Spectacular C/2006 P1 (McNaught) at m-5.5!

● High-resolution images of dust tail and striae

Five SOHO-discovered Kreutz-group comets

● Visible prior to their LASCO C3 appearance!

● HI-1 more sensitive than LASCO C3

SECCHI – Early Results:HI-1 Observations

SECCHI – Early Results:COR-2 Observations

● Apparent limiting magnitude: at least m11

Lots of stars● Observed comets:

Surprisingly few!

Over 40 “SOHO” Kreutz have passed through COR-2

● We have seen just four of them

What's the problem?● Exposure times? Bandpass?

Polarization?

● SECCHI: A salt-free diet? Kreutz comets show up well in the sodium-D

line (589.0nm, 589.6nm)● LASCO C3 (Clear) bandpass: 400-900nm● LASCO C2 (Orange) bandpass: 520-640nm● SECCHI COR-2 bandpass: 650-750nm● SECCHI HI-1 bandpass: 630-730nm

Sodium-D not visible in COR-2 or HI-1!

But...● HI-1 is more sensitive to Kreutz than LASCO C3

SECCHI – Early Results:COR-2 Observations

● So why so few COR-2 Kreutz comets? Polarized images?

● Kreutz still show in LASCO C2 polarized images, though are noticeably fainter

Exposure time?● LASCO C2 exposures are quadrupled for polarized

C2 images (to 100 secs)

● Answer: Probably both (but I think longer exposures

would really help...)

SECCHI – Early Results:COR-2 Observations

Scientific Potential

● 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

● Possible CME-comet interactions● First 3-D reconstruction of comets

SECCHI Object Discovery Prospects

● HI-2 Discoveries extremely infrequent

● Other surveys have it covered

● HI-1 Discoveries very likely and relatively frequent

● COR-2 Could still surprise us...

● COR-1 Very unlikely to make new discoveries due to

limited field of view

Some Highlights For This Year...

● Comet 2P/Encke Mag 6, will pass from HI-1A into HI-1B (also

LASCO C3) (late April)● Comet 96P/Machholz

Mag 8 (very approx), LASCO C3 (faint) and HI-1B (early April)

● C/1999 R1 = C/2002 R5 (SOHO) Predicted 3rd perihelion passage (~September) Mag 6; LASCO C2, C3 and (hopefully) HI-1B

● Many more asteroids...