Sun approaching comets

Matthew Knight has published his PhD dissertation on Studies of SOHO comets and this gives far more information on these comets than is given here.

Kreutz group comets

Over 1400 sungrazing comets of the Kreutz familly have been discovered on coronograph images from the SOHO spacecraft and it is the leading source of comet discoveries.

These are among the intrinsically faintest comets ever seen, with an absolute magnitude of around 20. They mostly represent minor fragments from the Kreutz group of sungrazing comets whose orbital evolution has been described by Brian Marsden (AJ 1967, 72:1170, 1989 98:2306). These comets have perihelion distance, q <0.02 AU, longitude of perihelion, L (L="longitude" of ascending node + arctan(tan(argument of perihelion) * cos(inclination)) around 282 degrees and latitude of perihelion, B (B="arcsin(sin(argument" of perihelion) * sin(inclination)) around 35 degrees. Only the larger objects survive perihelion, and then only if q> 0.005 AU.

In addition to the well documented sungrazers, which have orbits listed in the CBAT Comet Catalogue, there are numerous other poorly observed objects which may belong to the group. Some of these are documented by Kenelm England in a paper that appeared in the 2002 February BAA Journal. Kenelm has since found other recorded objects, which may belong to the familly, including this reference from IAUC 1221.

The comets probably orginated from the breakup of a comet seen in -371, which was reported to have fragmented into two parts by the Greek historian Ephorus. This breakup seems to have given rise to two main comets, one of which had a period of around 350 years and the other a period of around twice this. The shorter period object returned in the 1st, 4th, 8th and 11th centuries and may be identical with the comet of 1487. The 11th century return seems to have caused further breakup which gave rise to sub-group I of the Kreutz sungrazers. This group includes 1843 D1 (Great March Comet), comet Pereyra (1963 R1) and more recently the Solwind and SMM objects, and about 66% of the objects discovered by SOHO. The longer period object returned in the 4th century and in 1106 when it also broke up, to give rise to sub-group II comets including 1882 R1 (Great September Comet) and Ikeya-Seki (1965 S1), and about 18% of the objects discovered by SOHO. Comet White-Ortiz-Bolelli (1970 K1) appears to be belong to a slightly different sub-group of this grouping and may represent an earlier breakup.

The Kreutz groups have L around 282 and B around 35. L varies from 273 to 294 and B from 30 to 40, with group II tending towards higher L and lower B. Kreutz group I generally has q <0.007, and group II q>0.007. A plot of perihelion distance against longitude of perihelion shows the two groups, separated approximately by L=256 + 4000q. A plot of the argument of perihelion against the longitude of ascending node shows a continuous linear distribution, with possibly two or three closely spaced lines present. This may indicate possible reduction errors in the reference frames or indicate debris from separate break-ups.

The exact orbit of the comets on their return depends very much on what the solar system barycentre is doing at the time and this is largely controlled by the postion of Jupiter and Saturn. The breakup velocities were probably very small and objects may have remained gravitationally bound in orbit round each other or even in contact. The following images show the tracks of some of the objects: all comets 2000 - 2001 T-35 to T / all comets 2000 - 2001 T-2 to T / 2001 H1 - 2001 H4 T-2 to T / 2001 L1 - 2001 M9 T-2 to T. Rainer Kracht has plotted the actual tracks of all C3 Kreutz comets from 1996 to 2004.

Brian Marsden notes [March 2006]:

"One should not take the Kreutz q values at all seriously, although it is certainly possible--indeed probable--that some of them hit the sun, perhaps more likely now than six or seven years ago, when Jupiter was on the opposite side of the sun. I made this point years ago about the Pereyra Kreutz sungrazer in 1963, which was discovered and extensively observed beginning about three weeks after perihelion. But Jupiter, in moving the center of mass of the solar system away from the heliocenter as the comet was on its way in, allowed this. If the comet had instead come in 1969, it would have hit the sun, and we should never have observed it. Given that any Kreutz comet had to be safe from destruction on its previous pass, one can expect the perihelion distance to be as low as about 0.0042 AU."

Karl Battams notes in connection with Kreutz comets discovered by Solwind. [March 2006]:

Aside from that one exceptionally large one, Solwind found eight Kreutz from mag ~ -2 to 2 in five years, which is not entirely out of line with what SOHO has found. I can think of at least three or four comets as bright as -- if not brighter than -- SOHO-1087, with magnitudes of -1 to -2, assuming our photometry is not way off the mark. With an additional few SOHO Kreutz in the mag 2 to 0 range, this puts SOHO's and Solwind's 'bright Kreutz discovery rate' pretty much equal, implying (to me, at least) that the (temporal and spatial) distribution of these larger Kreutz fragments has changed little in 25+ years.

Zdenek Sekanina has recently published a paper on the SOHO comets in The Astrophysical Journal, Volume 566, Issue 1, pp. 577-598.

More than 300 sungrazing comets, most of them discovered with the Solar and Heliospheric Observatory (SOHO) coronagraphs since the beginning of 1996, are known to belong to the Kreutz group or system. Moving about the Sun in similar orbits, they are of indisputably common parentage and represent by far the most extensive data set in the history of investigations of cometary splitting. This study compares the SOHO sungrazers, which always disappear during their approach to the Sun, with the sungrazers detected earlier with the other space-borne coronagraphs (Solwind and Solar Maximum Mission [SMM]) as well as with the bright members of the Kreutz system, discovered from the ground between 1843 and 1970. Collected, summarized, and reviewed information on the sungrazers' light curves indicates that there is a difference of 20 mag (a factor of 108 in brightness) between the brightest sungrazer, C/1882 R1, and the faintest objects detectable with the SOHO instruments. The headless comet C/1887 B1 is suggested to be a transition object between the bright sungrazers and the coronagraphically discovered ones: its physical behavior was similar to that of the latter comets, but it survived the perihelion passage. This study also (1) examines temporal and spatial distributions of the SOHO sungrazers; (2) depicts correlations among their orbital elements; (3) distinguishes among tidally triggered, post-tidal, and terminal fragmentation; (4) reiterates the conclusion made in an earlier paper that post-tidal, secondary fragmentation events are occurring throughout the orbit, including the region of aphelion; (5) determines the relationship between a breakup's location in the orbit and the perturbations of the orbital elements of a fragment caused by the momentum it acquires during the separation from the parent; (6) shows that collisions of the Kreutz system comets with the Sun are clearly possible; (7) finds that minor fragments acquire enough extra momentum during each of the breakup episodes that their motions carry no ``memory'' of these events other than the most recent one; (8) offers a law for simulating the temporal distribution of these events; and (9) proposes a conceptual model scenario for the formation and evolution of the Kreutz system, including the process of progressive fragmentation. It appears that most of the mass is still locked in the major fragments (particularly C/1882 R1) and that therefore this comet system is relatively young. This paper is a first step in a massive investigation of the Kreutz system, which will combine deterministic and Monte Carlo techniques to verify the paradigms of the proposed conceptual model and eventually will develop a specific evolutionary scenario. This approach will account fully for effects of the planetary perturbations, where appropriate, and from time to time the results will be updated as the statistical sample of the SOHO sungrazers continues to grow.
Sekanina and Chodas have published further papers:
Fragmentation Hierarchy of Bright Sungrazing Comets and the Birth and Orbital Evolution of the Kreutz System. I. Two-superfragement model. Zdenek Sekanina and Paul W. Chodas, The Astrophysical Journal, 607:620-639, 2004 May 20
A back-and-forth orbit integration technique, developed for our previous investigation of the splitting of the parent of the sungrazers C/1882 R1 and C/1965 S1, is now applied in an effort to understand the history and orbital evolution of the Kreutz sungrazer system, starting with the birth of two subgroups, which show prominently among the bright members and whose inception dates back to the progenitor's breakup into two superfragments. The integration technique is used to reproduce the motion of comet C/1843 D1, the second brightest sungrazer known and presumably the most massive surviving piece of superfragment I, from the motion of C/1882 R1, the brightest sungrazer on record and arguably the most massive surviving piece of superfragment II. Running the orbit of C/1882 R1 back to AD 326, the progenitor comet is found to have split at a heliocentric distance of 50 AU and nearly 30 yr before perihelion. The superfragments acquired separation velocities of 8 m s1 in opposite directions. Using the same technique, we show next that (1) the motions of two additional sungrazers, C/1880 C1 and C/1887 B1, are matched extremely well if these objects shared a common parent with C/1843 D1, and (2) C/1963 R1 (Pereyra), the second brightest subgroup I member on record, is more closely related to subgroup II objects (such as C/1882 R1 and C/1965 S1) than to C/1843 D1. This finding raises serious doubts about the major role of the subgroups in the system's orbital history and offers an incentive for considering an alternative dynamical scenario. The fragmentation models for C/1963 R1 and two additional bright sungrazers, C/1945 X1 and C/1970 K1, suggest that (1) these comets may have been the most massive pieces of the fragment populations formed from their respective disintegrating parents, and (2) the course of evolution of the Kreutz system at the upper end of the mass spectrum may be better ascertained from the distribution of the sungrazers' arrival times than from the sources of subgroups. If so, the fragment hierarchy should be determined primarily by the cascading nature of the fragmentation process, which was recently shown by Sekanina to control the evolution of minor fragments as well. The sungrazer system's estimated age is in any case very short, less than 1700 yr.
Fragmentation Hierarchy of Bright Sungrazing Comets and the Birth and Orbital Evolution of the Kreutz System. II. The Case for Cascading Fragmentation. Zdenek Sekanina and Paul W. Chodas Astrophysical Journal, Volume 663(2007), pages 657 - 676
We examine the process of cascading fragmentation for the Kreutz sungrazer system to continue our exploration of its birth, orbital evolution, and temporal clumping. We modify and broaden the two-superfragment model from Paper I to include clusters of 30 bright comets spanning four centuries and 1000 SOHO sungrazers from 1996 to 2006. The spectacular parent sungrazer X/1106 C1 is assumed to have tidally split shortly after perihelion into a train of major protofragments immersed in a cloud of particulate debris, which at larger heliocentric distances were breaking up nontidally over and over again. We describe potential evolutionary paths for the Kreutz system by linking X/1106 C1 in subgroup Itype orbit with the comet of February 423 in one scenario or with the comet of February 467 in another. The latter scenario accounts for sungrazer clusters in as early as the 16th century, suggests that the progenitor object may have been observed as the comet of 214 BCE, is quite consistent with the orbital distribution of the SOHO sungrazers that sample the central filament of the Kreutz system between the clusters of major sungrazers, and predicts future clusters until 2120. Comet X/1106 C1 and the common parent of C/1882 R1 and C/1965 S1 were two first-generation fragments of the progenitor that split nontidally on the way to its 5th century perihelion, reminiscent of the superfragments in Paper I. We provide computational tools needed for solving the problem of the Kreutz system's orbital evolution, but no unique scenarios are presented for the individual comets. Another cluster of bright sungrazers is expected to arrive in the coming decades, its earliest member possibly just several years from now.

David Jewitt suggests that rotational fragmentation may be one factor in the destruction of the small (<50m diameter) nuclei of Kreutz and other comet group comets as they approach the Sun.  The spin-up time for destruction would be only about 1.5 days.

Sekanina published a further paper "UNPRECEDENTED DAYLIGHT DISPLAY OF KREUTZ SUNGRAZERS IN AD 363?" suggesting that multiple comets that were seen in November 363 were Kreutz sungrazers from a breakup that had occurred at the previous aphelion.
In the context of the recently proposed contact-binary model (Sekanina 2021), I investigate the circumstances of the first perihelion passage of the Kreutz sungrazers in orbits with barycentric periods near 735 yr, following the initial near-aphelion splitting of the presumed progenitor, Aristotle’s comet of 372 BC. Given favorable conditions at this breakup and at episodes of secondary fragmentation in its aftermath, the fragments should have arrived at their first perihelion nearly simultaneously, reminiscent of the anticipated outcome for the two-superfragment model’s perihelion return of AD 356 (Sekanina & Chodas 2004). The relevant case of a swarm of Kreutz sungrazers is examined to appraise possible scientific ramifications of the brief remark by Ammianus Marcellinus, a Roman historian, that “in broad daylight comets were seen” in late AD 363, only seven years later. The tested scenario, which does not contradict Ammianus’ narrative and is consistent with the contact-binary model, involves a set of ten sungrazers visible in the daytime, all reaching perihelion over a period of 4.6 days. As part of this work, I comment on the role of the rapidly developing, brilliant post-perihelion tail; revise the apparent magnitude typical for the first and last naked-eye sightings; compare the visibility conditions in full daylight, in twilight, and at night; and, for the first time, present circumstantial evidence that favors comet X/1106 C1 as the parent to C/1843 D1 rather than to C/1882 R1 and C/1965 S1.

SOHO has discovered around 200 comets that were not Kreutz sungrazers (16% of all SOHO comets) . The majority were discovered with the LASCO coronagraphs, though 1997 K2, 2000 S5, 2002 O6 and 2004 H6 were discovered with the SWAN uv imager. Only 1998 J1, 2002 O6 and 2004 H6 have been observed from the ground.

Meyer group comets

Maik Meyer has discovered that comets 1997 L2, 2001 E1 and 2001 X8 are related. Other comets which are members of this 'Meyer' group of comets are listed here. Any major member of this group would probably have passed un-noticed from the northern hemisphere as the orbit favours observation from the southern hemisphere. Rainer Kracht has generated these tracks showing the path of these comets with respect to the Sun. This group of comets has L ~ 280, B ~ 53, q ~ 0.04 AU and i ~ 70.

Brian Marsden notes on MPEC 2002-C28 that:

While 2002 C3, like some 95 percent of the comets discovered by SOHO, is clearly a member of the Kreutz sungrazing group, it is rather less appreciated that as many as 11 of the two dozen or so non-Kreutz comets discovered by SOHO also seem to be interconnected. The close temporal pairs C/2000 C2-2000 C5, C/2000 C3-2000 C4 and C/2000 Y6-2000 Y7 were remarked on when these comets were announced (cf. MPEC 2000-C52, 2000-C53 and 2001-B08). There is also the pair C/1999 J6 (MPEC 2000-F30) and C/1999 U2 (MPEC 1999-U29), comets with i = 27 deg separated by more than five months. M. Meyer was the first to point out the similarity between the orbits of C/1997 L2 (MPEC 1997-M06, MPC 35205) and C/2001 X8 (MPEC 2002-B01, MPC 44505), comets with i = 72 deg separated by 4.5 years; it also appears that the poorly observed comet C/2001 E1 can be associated with this pair, if the orbit with i = 107 deg on MPEC 2001-F52 is replaced by the one with i = 73 deg on MPC 44505.

Marsden group comets

Marsden further notes in IAUC 7832 that 1999 J6, 1999 U2, 2000 C3 and 2000 C4 form a group with q=0.049 and i=25. Other members are listed here. This group of comets has L ~ 280, B ~ 10, q ~ 0.05 AU, and i ~ 13.

Members of this group can pass quite close to the Earth if they have perihelion around May 11 - 12. If they survive perihelion, they then make a close approach to the Earth around June 10 - 11 and would become visible from the northern hemisphere. Otherwise members of this group are best seen from the southern hemisphere.

Comet 1999 J6 fills this criterion and is a new addition to the list of close earth approachers. With T = 1999 May 11.59 the comet could have reached 11th magnitude between 1999 June 9 and 11. It was 0.024 AU from the Earth on 1999 June 10 at around 14 UT, which is the 3rd closest recorded approach to the Earth by a comet [but see below]. It would have been brighter than 20th mag until early July. Unfortunately the LINEAR skyplot shows that the comet was outside their observing region in June and probably too faint by July.

Brian Marsden notes on MPEC 2004-X73 [2004 December 14] that:

Although the orbits computed for the SOHO comets that are members of sungrazing groups other than Kreutz have hitherto necessarily been assumed to be parabolic, the low orbital inclinations and the indicated associations with meteor streams suggest that the members of the Marsden and Kracht groups, at least, are of short period (which still means that e is no smaller than 0.98). If so, it might now be the case that individual members can be recognized at more than one perihelion passage. Furthermore, the implied success in having at least one member survive perihelion passage would provide an obvious mechanism for the continued maintenance of these comet groups.

It is eminently possible that C/2004 V9 is in fact identical with C/1999 J6 (cf. MPEC 2000-F30). To demonstrate this, the following represents a tentative linkage of the observations. Since there is a well-known inconsistency between the C3 and C2 observations, only the latter (i.e., those of the 1999 comet made on May 11.46257 UT and earlier and those of the 2004 comet on Nov. 8.35423 and earlier) have been used, the resulting residuals being very comparable to those of the individual parabolic solutions. It should also be noted that the object would have passed only 0.0091 AU from the moon and 0.0087 AU from the earth [closest ever recorded pass] on 1999 June 12.22 and 12.31 UT, respectively.

Epoch 1999 May 22.0 TT = JDT 2451320.5
T 1999 May 11.58356 TT                                  MPC
q   0.0491317            (2000.0)            P               Q
n   0.17952782     Peri.   22.21043     -0.20252199     -0.87330037
a   3.1120618      Node    81.80049     +0.81764025     -0.39980558
e   0.9842125      Incl.   26.59424     +0.53893345     +0.27839172
P   5.49

Epoch 2004 Nov. 11.0 TT = JDT 2453320.5
T 2004 Nov. 8.56075 TT                                  MPC
q   0.0490617            (2000.0)            P               Q
n   0.17940682     Peri.   22.31612     -0.20213975     -0.87355162
a   3.1134609      Node    81.67998     +0.81732637     -0.39954766
e   0.9842421      Incl.   26.58223     +0.53955270     +0.27797346
P   5.49
Earlier computations, by both Brian Marsden and P. Chodas, Jet Propulsion Laboratory, had suggested linkages among C2 observations of Kracht Group comets, namely, the possibility that C/1999 M3 (MPEC 2002-E18) = C/2004 L10 (MPEC 2004-O05) and that C/1999 N6 (MPEC 2002-F03) = C/2004 J4 or C/2004 J18 (MPEC 2004-M71, 2004-N05).
Comet 1999 J6 was around 7th magnitude in the LASCO C3 and faded quite rapidly. This suggests that it would probably not be brighter than 13th magnitude during its close approach. It would have been very favourably placed for northern hemisphere observers on 1999 June 11/12 and 12/13, crossing across half the sky during this time and passing some 6 degrees from the pole.

A further linkage between members of the Marsden group seems likely, as Brian notes on MPEC 2005-E87 [2005 March 15]:

Despite the parabolic orbit solutions, it seems quite likely that C/2005 E4 is identical with C/1999 N5 (cf. MPEC 2002-F03). The tentative linkage of just the C2 observations (which in the case of C/1999 N5 are those made on July 11.56347 UT and earlier) gives a period of 5.66 years with perihelion at 0.0492 AU.

In support of the proposed identification, as well as of the proposed identification C/1999 J6 = 2004 V9 (cf. MPEC 2004-X73), the respective orbits have been run back one further revolution (to Epoch 1993 Nov. 29.0 TT). The tabulation below shows in particular the remarkable agreement of the perihelion times T (as well as of the perihelion distances q). Indeed, this circumstance shows, not only that C/1999 J6 and C/1999 N5 probably separated from each other around that perihelion passage (the remaining slight discordances being understandable on account of the poor quality of even the C2 observations), but also that the splitting scenario discussed here and on MPEC 2004-X73 is in fact likely to be essentially correct. The comets passed 1.3-1.4 AU from Jupiter in May 1996.

Orbital elements:
Comet            T              q       e       Peri.    Node     Incl.     C
CJ99J060   1993 Nov.  22.66   0.0515   0.9834   21.01    83.36    28.34     X
CJ99N050   1993 Nov.  20.98   0.0515   0.9838   21.17    83.10    28.10     X
Three further faint members of this related group of comets (C/1999 P6, C/1999 P8, C/1999 P9: cf. MPEC 2002-F43) were observed during 1999 Aug. 5-15; and C/1999 U2 (MPEC 1999-U29), one of the brighter original prototypes (with C/1999 J6, cf. MPEC 2002-C28), was observed on 1999 Oct. 25. Although neither the chance of survival nor the specific manner in which these members evolved from the original parent body is known, it seems likely that C/1999 U2, at least, will be reobserved on its next return to perihelion, presumably during the next few months. If this comet indeed separated from C/1999 J6 and C/1999 N5 near perihelion around 1993 Nov. 20-22, it should have a period (now) of 5.95 years (i.e., near 2:1 mean-motion resonance with Jupiter) and return to perihelion within a few days of 2005 Oct. 8.
If this prediction does indeed come true, it would be highly appropriate to name the precursor as "Comet Marsden".

Rainer Kracht notes that 1996 V2 may be the previous return of 2002 V5.

Kracht group comets

Several further comets (including 1999 M3, 1999 N6, 2000 O3 and 2001 Q7) form a broader group of which the Marsden group is a tight subset and are listed here. This grouping was proposed by Rainer Kracht. This group of comets has L ~ 280, B ~ 10, q ~ 0.05 AU and i ~ 25.

Rainer notes that many of the Kracht group comets seen in 1996 and 2002 can be linked by single orbits, and predicts that they should return in 2008, although some may be too faint to be seen. He suggests returns as follows :

C/2002 N2  2008 Feb 12/13
C/2002 Q8  2008 May 12/13 = 2008 E4 (March 4)
C/2002 Q10 2008 May 16
C/2002 S4  2008 Jun 28
C/2002 S5  2008 Jun 30
C/2002 S7  2008 Jul 03/04 = 2008 N4 (July 4)
C/2002 S11 2008 Jul 22/23 = 2008 G6 (April 12)
He has analysed the orbits and suggests that it takes around 90 years to progress from Marsden group type orbits to Kracht group type orbits. He has a web page illustrating the evolution. He also notes that 2002 Q8 and 2002 S11 have remarkably similar orbital evolution and may have split from a progenitor object sometime between 1966 and 1972.

Rainer has made a page about the light curves of the "Kracht2 group" comets based on M. Knight's data (with his permission). He has improved his own magnitude measurements (with better background subtraction and including the vignetting corrections) and added his own light curves of C/2002 R5 = C/2008 L6 and L7. He notes that this comet seems to have been dormant at its 1996 return and that perhaps there are also dormant Kracht and Marsden group comets, which will show up unexpectedly in the future.

Rainer provided more information on 2009 May 12:

With the identification C/1996 X3 = 2002 S7 = 2008 N4 we have the first Kracht group comet observed in three apparitions and the first group comet showing nongravitational forces. It should be clear that the identity with 1996 X4 or X5 is also possible. The above linkage just gives the best fit to the observations and requires the smallest nongravitational force for this linkage.

It's disturbing that C/1996 X4 and X5 weren't observed at their returns in 2008. The two Kracht comets closest in time to C/2002 S7 are C/2002 S4 and S5. Their observations can be linked with those of C/1996 X4 and X5 and result in perihelion passages of 2008 June 28.4 and 30.5. I have searched again through the LASCO C2 images of 2008 June 27 to July 01 and have found nothing there.

But the close temporal spacing of C/2002 S4 and S5 to S7 makes it very probable that they are the return of C/1996 X4 and X5. If this is true then the identification C/2002 S4 = 2008 R7 must be wrong (and C/2002 S5 = 2008 R7 must be wrong).

Brian Marsden ( wrote: "The Kracht-group comet C/2008 R7 is likely to be a return of one of the members of Sept. 2002. R. Kracht himself suggests identity with C/2002 S5. Identity with C/2002 S11 is a distinct possibility, although this comet was associated with C/2008 G6 on MPEC 2008-L29.

I had suggested that C/2002 S11 = 2008 G6 ( on the basis that I could not find another linkage with one of the 2002 comets. C/2002 S11 and 2008 R7 are the two brightest Kracht group comets observed until now and Brian Marsden is certainly right in saying that this identity is a "distinct possibility". Actually the observations of C/2002 S11 and 2008 R7 can be linked with satisfying residuals.

If C/2002 S11 = 2008 R7 is true, where is the precursor of C/2008 G6? An obvious candidate is C/2002 Q10. When I tried again the linkage of C/2002 Q10 = 2008 G6 it didn't work. But after I had removed the first two C2 observations of C/2008 G6 without suitable reference stars the linkage was very good with a mean residual of 7" (these first two C2 observations are also omitted in Brian's solution of C/2002 S11 = 2008 G6).

So it seems that we have some probable new identifications:

C/1996 X4 = 2002 S4
C/1996 X5 = 2002 S5
C/2002 Q10 = 2008 G6
C/2002 S11 = 2008 R7
Orbital elements are at the bottom of this page:

Predicted returns

Sebastian Hoenig made two predictions for returns of comets seen in SOHO images. He identified 1999 R1 with 2003 R5 and predicted its return around 2007 September 11. It returned as predicted. He also noted that 2002 R5 had similar orbital elements and predicted that it might return some time between July and September 2006 [it was not observed, although there were data gaps].

Other comets

LASCO observed comet 96P/Machholz at perihelion (1996 October 11 - 19) and found it a little brighter than expected. The comet was also visible in C3 from 2002 January 6 to January 10, and reached -2 mag at perihelion on January 8 thanks to favourable forward scattering geometry, when it was at the margin of the C2 field. It also observed comets 1996 B2 (Hyakutake) (1996 April 29 - May 6), 1996 J1 (Evans-Drinkwater) (1996 December 21 - 1997 January 9) and 45P/Honda-Mrkos-Pajdusakova (1996 January 11 - 18).

SWAN observed comet 46P/Wirtanen in 1997 February and has observed many other comets including 2P/Encke, 19P/Borelly, 1995 O1 (Hale-Bopp), 1996 B2 (Hyakutake), 1997 N1 (Tabur), 1997 O1 (Tilbrook), 1998 J1 (SOHO), 2001 MD7 (P/LINEAR), 2002 T7 (LINEAR), 2002 X5 (Kudo-Fujikawa), 2007 W1 (Boattini), 2008 A1 (McNaught). Details of the discovery of 1997 K2 appear in Nature, Vol 405, 2000 May 18. It also discovered 2000 S5. Comet 2004 H6 was discovered in SWAN imagery by XingMing Zhou, Cazimieras Cernis and Michael Mattiazzo amongst others. It was an obvious object prior to the discovery announcement, which was delayed awaiting ground based confirmation and precise astrometry. Comet 2004 V13 was also discovered in SWAN imagery by Michael Mattiazzo and confirmed in LASCO imagery. It appeared as a 6th magnitude object, with tail and had brightened to 4th magnitude by December 17. Currently visible in SWAN are shown on the SWAN comet tracking page. SWAN images are available.

2P/Encke was visible in C3 from 2000 September 5.2 to 16.5 and in C2 from 2000 September 9.7 to 11.7. Pre perihelion it was 8th mag, but suddenly brightened to 6th magnitude after perihelion. It passed on the far side of the sun, which gives favourable conditions for the 'opposition effect' brightening, which clearly occurs with the Kreutz group comets. Comet 2P/Encke has never been observed at perihelion before. 2000 W1 (Utsunomiya-Jones) crossed the C3 field between 2000 December 28 and 2001 January 4. Comet 2002 X5 (Kudo-Fujikawa) was visible from 2003 January 25 to 31. Comet 2002 V1(NEAT) was visible from 2003 February 16 to 20 and is one of the brightest comets so far observed by SOHO. 2004 F4 (Bradfield), which passed through the field between 2004 April 16 and 2004 April 20, was also very bright, reaching around -2 thanks to strong scattering. This increased brightness compared to the light curve at greater elongation may explain the apparently anomolous sighting of comet Kohoutek from Skylab.

2003 K4 (LINEAR) transited C3 between 2004 September 27 and October 13, when it was around 7th magnitude. 2004 R2(ASAS) was simultaneously visible from 2004 October 5 to 10 at a similar magnitude. 2006 P1 (McNaught) saturated the detectors as it passed through the field over 2007 January 11 - 15.

LASCO was able to image other comets. 45P/Honda-Mrkos-Pajdusakova entered the field around 2006 July 7 and may be visible for 10 days as it faded below visibility. 96P/Machholz was again visible from 2007 April 1 to April 7, however it was much fainter on this return as the geometry did not produce favourable forward scattering.

Comet 2010 X1 (Elenin) will pass through the C3 field between 2011 September 22 and 30, when it may be 6th magnitude.

The major planets regularly pass through the field of view, and most are usually obvious. Mercury can be quite faint when it passes through at inferior conjunction. Mercury, Venus, Jupiter and Saturn were all visible for a few days in C3 in mid May 2000. Uranus and Neptune are also visible.

1 Ceres was visible in November/December 2000 and February 2002, 3 Juno in 2001 April/May at 9th mag, 4 Vesta in C3 in October 1999 and March/April 2001 at 8th mag. Other minor planet passes through C3 in the next few years are listed here. Note that the dates are generally only approximate and may be a day or so in error.

Other useful SOHO comet pages

  • SOHO/LASCO comet observations
  • Log pages for recent SOHO finds
  • Maik Meyer
  • Michael Oates
  • Sebastian Hoenig

  • Rainer Kracht

    Updated 2022 February 3

    Published by Jonathan Shanklin. Jon Shanklin -