BAA Comet Section : Comets discovered in 2005

Updated 2008 October 2

The equations for the light curves of comets that are currently visible use only the raw observations and should give a reasonable prediction for the current brightness. If the comet has not yet been observed or has gone from view a correction for aperture is included, so that telescopic observers should expect the comet to be fainter than given by the equation. The correction is about 0.033 per centimetre. Values for the r parameter given in square brackets [ ] are assumed. The form of the light curve is either the standard m = H0 + 5 log d + K0 log r or the linear brightening m = H0 + 5 log d + L0 abs(t - T + D0) where T is the date of perihelion, t the present and D0 an offset, if L0 is +ve the comet brightens towards perihelion and if D0 is +ve the comet is brightest prior to perihelion.

Observations of new comets are given in ICQ format. More recent ones may be available in TA format from the main page.

Full details of recently discovered objects will not appear until they are available on the CBAT web pages, which is usually a fortnight after the publication of the IAUC.

Brian Marsden comments on MPEC 2005-X14 [2005 December 3]

It seems likely that the Kracht-group comet C/2005 W4 is a return of C/2000 O3 (cf. MPEC 2000-Q09), a suggestion made by S. Hoenig before the observations above were available. The orbital linkage utilizes just the C2 observations (those from July 30.89596 onward in the case of C/2000 O3); although only the first three C/2005 W4 observations were obtained with C2, the residuals of the C3 observations are not systematically displaced.

For further information on the discovery of these objects see this year's SOHO discoveries.

Although Marsden gives a parabolic orbit for C/2005 E4 on MPEC 2005-E87 [2005 March 15] he also notes:

Despite the parabolic orbit solutions, it seems quite likely that C/2005 E4 is identical with C/1999 N5 (cf. MPEC 2002-F03). He gives a 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), which has a period of 5.66 years and 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.

Brian Marsden further predicts on MPEC 2005-H24 [2005 April 22]

Further to the statement at the end of MPEC 2005-G94, it should be noted that the best fit of C/2005 G2 to earlier comets is to C/1999 N5, the resulting orbital solution uses C2 observations alone, although the C3 observations do not show any systematic departure above 1 arcmin.

On MPEC 2005-E87, C/1999 N5 was linked (with comparable residuals) to C/2005 E4. It therefore seems plausible that C/2005 G2 separated from C/2005 E4 around the time of the C/1999 N5 perihelion passage, in much the same manner that C/1999 N5 may have separated from C/1999 J6 around a mutual Nov. 1993 perihelion passage. If C/1999 P6 (cf. MPEC 2002-F43) also separated at that 1993 perihelion passage, it should return (if it has survived) within a few days of 2005 Apr. 28 (likewise for C/1999 P8 and P9 around 2005 May 18).

Marsden group comet 2005 W1 has been linked to 2000 C4. Brian Marsden notes on MPEC 2005-W07 [2005 November 18]

It seems probable that this comet is identical with C/2000 C4 (MPEC 2000-C52; alternative direct orbit chosen on IAUC 7832 and MPC 44860), although it is conceivably identical with C/2000 C3 or C/2000 C7, which appeared around the same time (and, if they still exist, are also presumably about to return).

Brian Marsden notes on MPEC 2005-X14 [2005 December 3]

Comet C/2005 W5 has not been satisfactorily linked to a Marsden-group candidate at its previous perihelion passage, although potential fits to the various 1999 members seem preferable to those involving the comets of Feb. 2000 (cf. MPEC 2005-W07).

Further to the note about C/2005 W5 at the end of MPEC 2005-X14 and its possible linkage to one of the Marsden-group comets of 1999, Z. Sekanina and P. Chodas, and also R. Kracht, have suggested that a fit to C/1999 U2 seems most likely. The linkage, giving a period of 6.10 years, is from the C2 observations. It should be noted that, although all the observations of C/2005 W5 are from least-squares cubic reductions (i.e., using 11 or more reference stars), in the case of C/1999 U2 this is true only for the observations shown with note 1 (rather than 2) in column 14. For the remainder it was necessary to make only quadratic reductions, and the observations from 1999 10 24.70145 onward are particularly unsatisfactory. Since the orbits below also reasonably represent the generally inferior C3 observations in both 1999 and 2005 (i.e., without systematic residuals above about 70 arcsec), it seems likely that the linkage is in fact correct.

For further information on the discovery of these objects see this year's SOHO discoveries.

R. Kracke reports the LINEAR discovery of a comet (discovery observation below). After posting on the `NEO Confirmation Page', other observers have confirmed the cometary nature on CCD images, including C. Jacques and E. Pimentel (Belo Horizonte, Brazil; 0.30-m reflector, Jan. 14.3 UT; coma diameter about 15" and a noticeable 75"-long tail in p.a. 313 deg) and J. Young (Table Mountain 0.6-m reflector, Jan. 14.5, moderate cirrus clouds; slightly elongated 12" coma of mag 15.0 and a 1'-long broad tail in p.a. 295 deg). [IAUC 8463, 2005 January 14]

Brian Marsden notes on MPEC 2005-F50 [2005 March 29] that

The "original" and "future" barycentric values of 1/a are +0.000218 and -0.000370 (+/- 0.000026) AU^-1, respectively.

An observation by Juan José González Suárez, observing with a 20cm SCT x100 on January 17.25 suggests that it is 11.5, significantly brighter than the LINEAR discovery magnitude. By early February southern observers were estimating it at 10th magnitude, with an estimate of 9th magnitude by mid February. By early March most observers were reporting it at 8th magnitude. There have been suggestions of an outburst, but this isn't entirely clear from the light curve. If one did occur, it was towards the end of March.

Observations by Spanish amateurs in July show that the comets nucleus has split, with Sekanina calculated separation having occurred around April 23. Jeremy Shears has reported the detection of the secondary condensation in the tail of the comet in images taken in early September. Visual observations suggest a total magnitude around 12.

42 observations received so far suggest a preliminary light curve of m = 8.5 + 5 log d + 10.2 log r

Observations in ICQ format, last observation 2005 May 12, updated 2005 June 1.

E. J. Christensen reports his discovery of a comet (discovery observation below; 10" tail in p.a. 250 deg) on images taken with the 0.68-m Schmidt telescope in the course of the Catalina Sky Survey. Following posting on the 'NEO Confirmation Page', J. Young reported that his CCD images taken through moderate cirrus clouds with the Table Mountain 0.6-m reflector on Jan. 16.5 UT show a 5" coma and a broad tail 25" long spanning p.a. 240-260 deg. M. Tichy found the object to be diffuse with a tail in p.a. 255 deg on images taken by himself and J. Ticha with the Klet 1.06-m telescope. [IAUC 8466, 2005 January 17]

An object reported as asteroidal by LINEAR (2004 Mar. 23) and by Spacewatch (2004 Mar. 18 and 26), and published as 2004 FS_101 (MPS 104028, 110712; initial orbit on MPEC 2004-O45 and MPO 66351) has been identified with C/2005 B1. [IAUC 8469, 2005 January 19]

Brian Marsden notes on MPEC 2005-K26 [2005 May 23] that

The "original" and "future" barycentric values of 1/a are -0.000013 and +0.000214 (+/- 0.000003) AU^-1, respectively

Brian Marsden notes on MPEC 2005-K27 [2005 May 23] that

The "original" and "future" barycentric values of 1/a are +0.000152 and -0.002367 (+/- 0.000031) AU^-1, respectively.

Observations by Juan José González Suárez" with a 20cm SCT show that the comet was around 11.5 in early September, though other observers have made it up to a couple of magnitudes fainter. Clear, transparent skies are essential to see the comet as it is still at a very low altitude for European observers.

59 observations received so far suggest a preliminary light curve of m = 6.8 + 5 log d + 8.5 log r

Somewhat as expected from the orbit this object has finally shown cometary characteristics. Alan Fitzsimmons using the 3.6-m NTT at ESO found that the object had a coma on 2005 May 10.0. Further observations, reported on MPEC 2006-A63 [2006 January 12] show a hyperbolic orbit with perihelion at 3.89 AU in early March 2007.

Brian Marsden notes on MPEC 2006-C63 [2006 February 11] that

The "original" and "future" barycentric values of 1/a are +0.000060 and -0.000021 (+/- 0.000005) AU^-1, respectively.

Brian Marsden notes on MPEC 2005-M21 [2005 June 20] that

The "original" and "future" barycentric values of 1/a are -0.000028 and +0.000003 (+/- 0.000043) AU^-1, respectively.

Brian Marsden notes on MPEC 2005-O04 [2005 July 18] that

The "original" and "future" barycentric values of 1/a are +0.022106 and +0.022575 AU^-1, respectively.

The comet will pass 0.056 AU from Earth on 2058 June 17, and will be less than 0.1 AU from Earth between the 8th and 26th.

Brian Marsden notes on MPEC 2005-O05 [2005 July 18] that

The "original" and "future" barycentric values of 1/a are -0.000011 and -0.000097 (+/- 0.000044) AU^-1, respectively.

Several observers, including Giovanni Sostero and José González reported visual observations, putting at around 12 - 12.5 in early June. On June 8/9 Nicolas Biver and José González reported that it had brightened further to around 10th magnitude and had become more condensed. Two days later I estimated it at 9th magnitude. On June 13.98 it was 8th magnitude in 20x80B, although summer twilight is making the northern sky quite bright. Observations over June 15 - 19 are scattered, but suggest that the comet faded rapidly.

Images by David Strange, Michael Jager & Gerald Rhemann and Giovanni Sostero & Ernesto Guido over June 12 - 14 suggest the presence of a secondary condensation, implying that the comet had split. Calculations by Zdenek Sekanina suggest that the split took place around April 22. Whilst this may have facilitated the rapid brightning seen in June, it was clearly not the primary cause.

An image to 16th magnitude taken by Michael Mattiazzo on August 1st does not show 2005 K2, suggesting it has disintegrated.

18 observations give a preliminary light curve of 15.4 + 5 log d + 46.9 log r
This suggested that the comet could reach at 5th magnitude at perihelion, however fading seems to have set in after mid June, with the comet peaking at around 8th magnitude.

An improved orbit by Hirohisa Sato has increased the period to 10.0 years with perihelion at 1.54 AU in August. Further observations have decreased the period to 7.1 years with perihelion at 1.51 AU in mid August.

Brian Marsden notes on MPEC 2006-C64 [2006 February 11] that

The "original" and "future" barycentric values of 1/a are -0.000390 and +0.000198 (+/- 0.000018) AU^-1, respectively.

Brian Marsden notes on MPEC 2005-P57 [2005 August 15] that

The "original" and "future" barycentric values of 1/a are +0.000049 and +0.000279 (+/- 0.000010) AU^-1, respectively.

23 observations give a preliminary light curve of 6.1 + 5 log d + [5] log r

Further observations show that it is a periodic comet with period of 8.6 years and will reach perihelion at 2.93 AU in late January 2006. It has been identified in observations made by NEAT in 1997, so the orbit is now secure and the comet has received a numeric designation.

Brian Marsden notes on MPEC 2005-S06 [2005 September 17] that

The "original" and "future" barycentric values of 1/a are +0.001289 and +0.001814 (+/- 0.000038) AU^-1, respectively.

4 observations give a preliminary light curve of 8.5 + 5 log d + 22.9 log r

Further observations show that it is a short period comet with perihelion at 2.2 AU in mid December. The period is 6.8 years. It is unlikely to become brighter than 18th magnitude.

The latest orbit by Hirohisa Sato shows that it has a period of around 150 years.

Orbit calculations by Hirohisa Sato suggested the possibility of an elliptical orbit, with period around 32 years, however as observations accumulated this possibility has receded. It does however move in a long period elipse, with a period around 270 years. He also provides an animation of SWAN images.

I was able to observe it on August 28.9 from a site outside Cambridge, with 0.20m SCT and 25x100B, estimating it at 10th magnitude, with a 2' diameter, diffuse coma.

Some observations reported on the internet suggest that it may be fading rapidly, whilst others indicate that it is fading slowly.

Brian Marsden notes on MPEC 2005-V86 [2005 November 14] that

The "original" and "future" barycentric values of 1/a are +0.000055 and -0.000047 (+/- 0.000048) AU^-1, respectively.

Brian Marsden notes on MPEC 2005-V89 [2005 November 14] that

The "original" and "future" barycentric values of 1/a are +0.001381 and +0.001431 (+/- 0.000246) AU^-1, respectively.

Brian Marsden notes on MPEC 2006-K48 [2006 May 26] that

The "original" and "future" barycentric values of 1/a are +0.000409 and +0.000360 (+/- 0.000005) AU^-1, respectively.

Brian Marsden notes on MPEC 2005-Y07 [2005 December 19]

Alternate orbit solutions are of course possible for the non-group comets C/2005 V8 and C/2005 Y1. The orbit of C/2005 V8 is possibly similar to that of C/2005 H7.

Brian Marsden notes on MPEC 2005-Y07 [2005 December 19]

Alternate orbit solutions are of course possible for the non-group comets C/2005 V8 and C/2005 Y1. The orbit for C/2005 Y1 is heavily weighted toward the C2 data, which for the most part are mutually unusually consistent, with the comet roughly of mag 7-8; the comet was much harder to detect in C3, and these reductions were unusually inconsistent. If this orbit is at all meaningful, a second entry into the C2 field should occur, although the phase angle would be very much larger and the magnitude obviously uncertain.

In October 2006, L Buzzi and other Italian amateur observers including Ernesto Guido, Giovanni Sostero, Rolando Ligustri and Sergio Foglia reported that the object had a coma and tail, and was around 15th magnitude. The comet may brighten by a further magnitude towards perihelion.

Brian Marsden notes on MPEC 2006-T62 [2006 October 12] that

The "original" and "future" barycentric values of 1/a are +0.005508 and +0.006832 (+/- 0.000006) AU^-1, respectively.

Further observations have shown cometary characteristics. The latest orbit shows that perihelion was at 1.9 AU in early November 2005, with a period of 7.6 years.