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Latest News... Archive!

Fact-bites, stories, and points of interest relating to SOHO comets and SOHO images.

October through December, 2005

Note: all external links open in new windows.

Dec 28, 2005 -- The family ties get stronger

On Dec23, 2005, an interesting MPEC relating to the Marsden-group comets was released. MPEC 2005-Y27 shows that the recent Marsden-group comet, SOHO-1062 (C/2005 W5) is almost certainly the return of C/1999 U2 (SOHO-90)! Initially, no linkage was found between W5 and any other known Marsden-group comets, but following suggestions from Z. Sekanina, P. Chodas, and R. Kracht, a link to C/1999 U2 was evaluated and found to be very likely correct. The orbital period of this object is approximately 6.1 years, which makes it somewhat longer than the "nominal" ~5.5yr orbit. Why is this, you ask? Well, the Marsden-group comets are known to take the comets very close to the Earth-Moon system (as noted in MPEC 2004-X73) and relatively close to Jupiter (c.f. MPEC 2005-E87), both of which could quite easily perturb the comet and push it into a slightly longer orbit. By my estimation, this now means that thirteen of the twenty-five known Marsden-group comets can (tentatively) be directly linked to at least one other member, as illustrated by the Marsden-group "family tree":
      --------------------------------- C/1993 ?? ----------------------------             
     |             |              |                 |                        |            
?C/1999 P6?    ?C/1999 P8?    ?C/1999 P9?     ---C/1999 N5---         ---C/1999 J6---    
     \             |             /            |             |         |             |      
    did not survive 1999 perihelion??      C/2005 E4   C/2005 G2   C/2004 V9   C/2004 V10 

and also: 
    C/1994 ??      C/1993 ??
       |              |
    C/2000 C4      C/1999 U2 
       |              | 
    C/2005 W1      C/2005 W5
Of course, the roots of this family go much deeper than this. It has been shown that the Masden-group is strongly related to another of SOHO's comet groups: the Kracht group. A small, but significant, number of close relationships have been shown to exist within the Kracht-group, most recently in MPEC 2005-X14, where C/2005 W4 (SOHO-1057) was shown to be the very probable return of C/2000 O3 (SOHO-189).

So is this where it ends? Well of course not! The Marsden and Kracht groups have been shown to also be related to the Quadrantid meteor stream, the Daytime Arietid stream, and possibly the Northern and Southern delta Aquarid streams. But wait, there's more! The Marsden-Kracht-Quadrantid-Arietid-Aquarid (!) family gained an new relative in 2003, namely the asteroidal object, 2003 EH1, believed to be the direct parent of the Quadrantids. Now, every important family needs an impressive figure-head, and this family is no exception. So, in the final twist of this tale, the arguably most impressive (known!) member of this group is the spectacular comet 96/P Machholz, pictured below.

image of comet 96P Machholz This image of comet 96P Machholz was captured by the LASCO C2 camera in January 2002.
More images from this event can be seen here. The LASCO C3 camera also caught many images of the comet at this, and its 1996, perihelion passage.

Hopefully, in years to come, many more interesting members will get added to this family and maybe then will we be able to fully understand the mechanisms which have formed this fascinating system!

Dec 27, 2005 -- Catching up...

The following comets have confirmed by Mr Sungrazer:
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1071  Dec 16,05 21:57:35  S.Farmer Jr  C2,C3   Non-grp  Dec16-17,05
1072  Dec 20,05 09:34:26  Q.Ye         C3,C2   Kreutz   Dec20,05
1073  Dec 20,05 18:50:24  S.Hoenig      C2     Kreutz   Dec20-21,05
1074  Dec 22,05 10:18:08  K.Battams     C2     Kreutz   Dec22,05
1075  Dec 22,05 10:21:32  K.Battams     C2     Kreutz   Dec22,05
1076  Dec 26,05 10:37:34  R.Kracht      C2     Meyer    Dec24-25,05
1077  Dec 26,05 11:29:29  R.Kracht     C3,C2   Kreutz   Dec24-25,05
1078  Dec 26,05 14:36:42  S.Farmer,Jr  C3,C2   Kreutz   Dec26-27,05
1079  Dec 27,05 02:02:41  Q.Ye          C2     Kreutz   Dec27,05
SOHO-1071 (later announced as C/2005 Y1) was a reasonably bright non-group comet spotted in C2 images immediately after LASCO recovered from scheduled spacecraft manuevers. It was very faintly visible in C3. Here is an animated gif of the comet in C2. There was speculation that it may reappear in C2 some time around Dec 22, but sadly that did not happen.
In addition to these confirmations, several new comets have been officially designated in recent MPECs, catching up somewhat on the not-so-small comet backlog that had accumulated of late... So, the MPEC's released were MPEC 2005-Y02 (comets SOHO-1037,1039,1040,1041), MPEC 2005-Y03 (comets SOHO-1042 to 1045), MPEC 2005-Y07 (comets SOHO-1046,1047,1071), MPEC 2005-Y14 (comets SOHO-1049 to 1051), MPEC 2005-Y15 (comets SOHO-1052 to 1055), MPEC 2005-Y22 (comets SOHO-1056,1058,1059).

Dec 14, 2005 -- Yet more confirmations and some MPEC news too...

The following comets were confirmed by Mr Sungrazer:
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1063  Dec 04,05 08:29:57  H.Su         C2      Kreutz   Dec03,05
1064  Dec 04,05 09:52:49  H.Su         C2      Kreutz   Dec04,05
1065  Dec 06,05 09:24:36  K.Cernis     C2      Kreutz   Dec06,05
1066  Dec 08,05 04:38:17  J.Ruan      C3,C2    Kreutz   Dec08-09,05
1067  Dec 08,05 04:47:46  J.Ruan       C2      Kreutz   Dec08,05
1068  Dec 09,05 08:04:29  H.Su         C2      Kreutz   Dec09,05
1069  Dec 12,05 09:22:00  Q.Ye         C2      Kreutz   Dec11-12,05
1070  Dec 12,05 17:37:48  R.Matson     C2      Kreutz   Dec12-13,05
This can be a busy period for SOHO comets as the Kreutz group is positioned in such a way that we see a lot of very small comets in the C2 images. This period will stop rather abruptly by the end of December. Then the comet discovery rate should slow down for a time.
The possible link between SOHO-1057 and C/2000 O3 (Kracht-group) was confirmed in MPEC 2005-X14. It looks like they are one and the same! In the same MPEC, the Marsden-group comet, SOHO-1062, was not successfully linked to any previously known Marsden-group member.
Also, on Dec 9, MPEC 2005-X52 and MPEC 2005-X53 were released. These covered the Kreutz group comets SOHO-1030 to SOHO-1036 and Meyer-group comet SOHO-1029.

Dec 01, 2005 -- More Confirmations

The following comets were confirmed by Mr Sungrazer:
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1057  Nov 23,05 04:29:31  B.Zhou      C2,C3    Kracht   Nov23-24,05
1058  Nov 23,05 09:21:26  T.Scarmato  C3,C2    Kreutz   Nov23,05
1059  Nov 25,05 11:30:25  H.Su        C3,C2    Kreutz   Nov25,05
1060  Nov 28,05 02:14:51  R.Matson    C3,C2    Kreutz   Nov28,05
1061  Nov 29,05 13:17:52  H.Su          C2     Kreutz   Nov29,05
1062  Nov 29,05 14:05:04  H.Su        C3,C2    Marsden  Nov29-30,05
Two very interesting comets amongst today's confirmations. The first is SOHO-1057, a bright Kracht-group comet, discovered by Bo Zhou. This is the first Kracht-group comet we have seen in nearly 18 months, and is one of the brightest Kracht-group members we have ever seen! What makes it even more interesting is that there is a strong possibility that this object is the return of C/2000 O3, another bright Kracht-group comet seen in 2000.
The other interesting comet is another bright Marsden-group comet. This object could be a fragment from the perihelion passage of C/2000 C4 which, as mentioned in the November 18, 2005 news, possibly returned just a couple of weeks ago as C/2005 W1!

November 22, 2005 -- Confirmations

The following comets were confirmed by Mr Sungrazer:
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1047  Nov 13,05 07:34:39  H.Su        C3,C2    Kreutz   Nov13-14,05
1048  Nov 17,05 09:45:50  H.Su        C3,C2    Marsden  Nov16-17,05
1049  Nov 18,05 10:11:16  T.Scarmato  C3,C2    Kreutz   Nov18,05
1050  Nov 19,05 06:32:59  W.Xu        C3,C2    Kreutz   Nov19-20,05
1051  Nov 19,05 06:39:39  J.Ruan      C3,C2    Kreutz   Nov19-20,05
1052  Nov 19,05 09:51:36  H.Su          C2     Meyer    Nov19,05
1053  Nov 19,05 15:12:59  T.Hoffman     C2     Kreutz   Nov19.05
1054  Nov 21,05 09:22:56  H.Su          C2     Meyer    Nov19-20,05
1055  Nov 21,05 09:49:17  Q.Ye          C2     Kreutz   Nov20,05 
1056  Nov 21,05 11:41:24  T.Scarmato  C3,C2    Kreutz   Nov21-22 
Congratulations are due to Jiangao Ruan and Wentao Xu, who both discovered their first SOHO comets this week! Interestingly, their comets were a very close pair of 'twins' that tracked side-by-side across LASCO-C3 and into LASCO-C2, before plunging into the Solar corona and evaporating!
These latest finds mean SOHO has made 160 comet discoveries so far this year!

Nov 18, 2005 -- Interesting MPEC released

SOHO comet #1048 was announced on MPEC 2005-W07. This comet was a bright member of the Marsden-group. What makes this one so intersting is that it is very likely to be the return of SOHO-101 (C/2000 C4)! This is the latest in a series of linkages made by Brian Marsden (founder of the "Marsden-group") of comets within the group. On a grander scale, Marsden-group comets are related to the Kracht-group comets and also comet 96/P Machholz and at least two meteor streams!

November 9, 2005 -- Confirmations

The following comets were confirmed by Mr Sungrazer:
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1039  Oct 30,05 13:15:32  H.Su         C2      Kreutz   Oct30,05
1040  Nov 02,05 11:07:21  H.Su         C2      Kreutz   Nov02,05
1041  Nov 03,05 19:11:51  H.Su         C2      Kreutz   Nov03-04,05
1042  Nov 04,05 10:04:28  T.Scarmato  C3,C2    Kreutz   Nov04-05,05
1043  Nov 07,05 15:06:07  R.Matson     C2      Kreutz   Nov07,05
1044  Nov 08,05 01:36:32  H.Su        C3,C2    Kreutz   Nov08-09,05
1045  Nov 09,05 03:17:08  H.Su         C2      Kreutz   Nov09,05
1046  Nov 09,05 11:04:42  H.Su         C2      Non-grp  Nov09,05
In addition the following X-Comets were 'confirmed':
XC51  Nov 06,05 15:16:33  H.Su         C2      Kreutz?  Nov06,05
XC52  Nov 08,05 22:40:07  T.Hoffman    C2      Kreutz?  Oct31,05 
These are the first x-comets in about a year, so it's very unusual that we have two of them! So what is an "X-Comet"? Well, it is an object that meets some of the criteria for being "real", but lacks a certain something. In the above two cases, XC51 was extremely faint and somewhat inconsistent in shape. I was able to follow it for maybe four images, but the fourth position was more of a guess. XC52 was only visible to me for three images, maybe four, but again was very inconsistent in shape and brightness. In both cases I was not convinced they were real, but am not going to completely exclude them from record.

October 29, 2005 -- More MPECs released

The following SOHO comets were announced on MPEC 2005-U85: C/2005 S6 (SOHO-1017, Su), C/2005 S8 (SOHO-1018, Su), C/2005 S7 (SOHO-1019, Ye), C/2005 S9 (SOHO-1020, Su), C/2005 S11 (SOHO-1021, Su), C/2005 S10 (SOHO-1022, Chen).
All comets belonged to the Kreutz group. Comets 2005 S9 and S11 were oddballs, with perihelion distances approximately twice that of the other Kreutz. This is because they are part of the extended population of Kreutz comets, known as "Sub-group II".

October 28, 2005 -- MPECs released

The following SOHO comets were announced on MPECs 2005-U71 and 2005-U72: C/2005 Q7 (SOHO-1007, Farmer,Jr.), C/2005 Q8 (SOHO-1008, Su), C/2005 Q9 (SOHO-1009, Farmer,Jr.), C/2005 Q10 (SOHO-1010, Zhou), C/2005 R5 (SOHO-1013, Su), C/2005 R6 (SOHO-1014, Su), C/2005 R7 (SOHO-1015, Su), C/2005 S5 (SOHO-1016, Su). All were Kreutz except Q8, which was a Meyer-group comet.

October 26, 2005 -- Confirmations

The following comets were confirmed by Mr Sungrazer. C/2005 T4 (SWAN) was designated as SOHO-1038:
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1030  Oct 14,05 14:13:53  H.Su         C2      Kreutz   Oct14,05
1031  Oct 14,05 23:05:14  T.Hoffman    C3,C2   Kreutz   Oct15-16,05
1032  Oct 18,05 00:13:27  H.Su         C3,C2   Kreutz   Oct18,05
1033  Oct 18,05 11:02:47  H.Su         C3,C2   Kreutz   Oct18-19,05
1034  Oct 19,05 09:49:27  H.Su         C2      Kreutz   Oct19,05
1035  Oct 21,05 12:31:03  T.Scarmato   C3      Kreutz   Oct21,05	
1036  Oct 23,05 09:39:09  B.Zhou       C3,C2   Kreutz   Oct23,05
1037  Oct 24,05 10:12:33  Q.Ye         C2      Kreutz   Oct24,05
1038  --- N/A  --- R.Matson,M.Mattiazzo --- SWAN --- Non-grp ---

October 23, 2005 -- New SOHO/SWAN comet announced!

The SWAN instrument, on-board SOHO, has made it's seventh comet discovery! C/2005 T4 (SWAN) was announced in MPEC 2005-U19, and is the second SWAN comet found in the past two months! Unlike LASCO, none of SWAN's discoveries belong to any known group of comets. Rob Matson (co-discoverer of C/2005 T4 (SWAN), along with Michael Mattiazo) gives the following account of the discovery:

"It was an exciting time last week. I discovered the comet Monday afternoon 10/17, computed RA/Dec positions and forwarded to Brian Marsden at MPC. Having been fooled by SWAN comets submitted by others that have gone unconfirmed in the past, and given the very dim nature of this one, Brian was unsure it was real and reluctant to put it on the NEO confirmation page. So instead, I contacted Sebastian Hönig and Maik Meyer to see if weather would permit them to try to recover it telescopically. It was too low in the southwest for Sebastian, and Maik had poor weather all of last week.

Seeing that the comet was better placed for the southern hemisphere, I contacted my friend/colleague Rob McNaught to see if he could give it a try. He was clouded out Tuesday and Wednesday, but last Thursday it was clear. He forwarded my coordinates and search zone to Eric Christensen (LPL) who said he'd take a 6 x 9 degree strip centered on my zone.

Well, neither saw it Thursday night, which began to concern me. In the mean time, however, McNaught let me know that on Wednesday he was contacted by Michael Mattiazzo who reported more or less the same four coordinates to him. (Rob let him know that I had already forwarded the candidate to MPC.) Michael had taken some images trying to find it, but so far w/o success. So at least he and I were in agreement that the object was real (and Maik also felt quite confident it was legit).

Thursday night and Friday morning I did a sensitivity analysis of the 4 positions and the resulting propagated orbit, and determined that my zone needed to be expanded to cover worst case uncertainties. Comparing against the image centers that Eric took Thursday night, I advised him to search west of his prior night's swath. He kindly agreed to give it another try, and bingo -- he found it! It was actually even further west than I expected, which I came to realize was due to the completely unknown epochs of the SWAN zones containing the comet. (Each SWAN scan takes the better part of a day, and unfortunately they don't provide any information to the user community as to the start time of the scan or the scan pattern.) With Eric's precision astrometry, Rob had no trouble finding it 6 hours later in Australia."

Congratulations Rob and Michael! Below are two images of the comet, very kindly supplied by Eric Christensen and Rob McNaught.

The image on the left is 3-image stack of 20-second exposures of the comet, coadded along the direction of motion. Images were taken by Eric Christensen with the 0.68-meter Schmidt of the Catalina Sky Survey at the University of Arizona.
The image on the right is a stack of 6x30sec exposures. (Field is ~3'.6 x 3'.6, north to left and east down). Images were taken by Rob McNaught at Siding Spring, New South Wales, with the 1-meter telescope.
Eric Christensen, 2005 Robert H. McNaught RSAA/ANU (c) 2005

October 11, 2005 -- Confirmations and congratulations...

The following comets were confirmed by Mr Sungrazer.
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1028  Oct 06,05 11:31:20  H.Su         C3,C2   Kreutz   Oct06,05
1029  Oct 08,05 03:30:55  H.Su         C2      Meyer    Oct08,05

Congratulations are due to Hua Su -- SOHO-1029 is his 50th SOHO comet discovery! What makes is achievement all the more incredible is that he only began searching the SOHO images just over a year ago! He is already in the top 10 of comet hunters for the most comets discovered. Well done, Hua!

October 8, 2005 -- MPECs released

The following SOHO comets were announced on MPEC 2005-T55: C/2005 P4 (SOHO-1001, Hoffman), 2005 P5 (SOHO-1002, Su), 2005 P6 (SOHO-1003, Su), 2005 Q5 (SOHO-1004, Farmer,Jr.), 2005 Q6 (SOHO-1005, Su). All were Kreutz except Q6, which was a non-group comet.

October 5, 2005 -- Confirmations

The following comets were confirmed by Mr Sungrazer.
Soho#  Date/Time of Post  Discoverer   Tel     Group    Images of...
1024  Sep 27,05 14:12:27  H.Su         C3,C2   Kreutz   Sep27-29,05
1025  Sep 29,05 19:40:26  B.Zhou       C3,C2   Kreutz   Sep29-30,05
1026  Oct 01,05 17:43:40  H.Su         C3,C2   Kreutz   Oct01-02,05
1027  Oct 04,05 10:37:50  B.Zhou       C3,C2   Kreutz   Oct04,05