BAA Comet Section : Not yet numbered objects

Updated 2013 September 13


Note following the IAU convention announced in the 14th comet catalogue, numbers following the names of discoverers are no longer used.
  • P/PanSTARRS
  • (596) Scheila
  • (3200) Phaethon
  • (3552) Don Quixote
  • S01P/SOHO (2007 R5)
  • S02P/SOHO (2008 K10)
  • S03P/SOHO 1997 J6)
  • S04P/SOHO (2008 N4)
  • S05P/SOHO (2000 C4 = 2011 ??)
  • S06P/SOHO (2003 T12 = 2012 A3)
  • S07P/SOHO (2002 R1 = 2008 A3)
  • Comets 1 - 99
  • Comets 100 - 199
  • Comets 200 - 299
  • Not yet numbered objects
  • When observing a comet please try to forget how bright you think the comet should be, what it was when you last viewed it, what other observers think it is or what the ephemeris says it should be.

    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 individual comets are given below, in ICQ format.


    Cometary asteroids

    (596) Scheila
    CBET 2583, issued on 2010 December 12, announced the discovery of a spiral like structure around main belt asteroid (596) Scheila by Steve Larson in the course of Catalina Sky Survey (CSS) with the Catalina 0.68-m Schmidt telescope, on images obtained on 2010 December 11.44. The cometary appearance has been confirmed by other observers. In the Catalina images, the "coma" is bright (~13.5 compared to the expected 14.2), and extends some 2 arcmin north and 5 arcmin west from the central condensation in a spiral like structure reminiscent of 29P in outburst. Recent images show a stellar appearance in October and November, but slight diffuseness on December 3.4.

    Radio observations from Arecibo between mid December and early January show no clear detection of OH emission in the 1667 MHz line. This may suggest that the cometary appearance was due to an impact event, or simply that gas emission was very weak.

    Jewett et al in a paper submitted to ApJL suggest that the activity was most likely due to impact with a 35m diameter body.

    The "Dictionary of Minor Planet Names" notes that (596) Scheila was discovered on 1906 February 21 by A. Kopff at Heidelberg. Named in honor of an acquaintance of the discoverer, a female English student in Heidelberg. (596) Scheila is a main-belt asteroid inclined roughly 14 degree on the ecliptic and it is now 3.1AU from the Sun and 2.5AU from the Earth. It is next at perihelion in 2012 May and has a period of 5.0 years. Its distance from the sun varies between 2.4 and 3.4 AU. It is about 117km diameter and has an abledo of 0.036.


    (3200) Phaethon Asteroid (3200) Phaethon has perihelion at 0.14 AU and has been suggested as a possible extinct comet nucleus. It is the parent body of the Geminid meteors. It was imaged by STEREO during its 2009 perihelion and appears to have been significantly brighter than expected at around the time of perihelion (June 20), suggesting the possibility of cometary activity.

    K. Battams, Naval Research Laboratory, writes that A. Watson (Werribee, Victoria, Australia) has commented that the minor planet (3200) was visible in SECCHI HI-1A images during June 17-22, noting a very short radial elongation (perpendicular to the direction of motion) that was possibly a line-of-sight effect related to its passage through a reasonably dense, higher-speed solar outflow stream. Battams adds that the apparent brightness of (3200) increased significantly (about 2 mag or more), peaking at mag perhaps 10-11 a few hours after perihelion (T = June 20.302 TT, q = 0.140 AU); 36 hr later, the object's had faded to magnitude roughly 13-14. Phaethon was also visible in HI-1B images during June 21-22. More formal photometry will be performed later. [IAUC 9054, 2009 June 29]

    Alan Watson recovered Phaethon in STEREO images from 2012 April 30 on May 3, noting that it seemed a little fuzzy.

    Dave Jewett and Jing Li suggest Phaethon is a "rock comet". They published a paper on the subject in The Astronomical Journal, with an an on line summary. Jewett et al in a paper submitted to ApJL suggest that by contrast the activity seen in (596) Scheila was most likely due to impact with a 35m diameter body.


    (3552) Don Quixote Asteroid (3552) Don Quixote was discovered 30 years ago and with a period of 8.7 years has been observed at three apparitions. It was classed as an Amor asteroid - one that crosses the orbit of Mars, and can make moderate approaches to Jupiter (0.6 au) and the Earth (0.3 au). It appeared anomalously bright in images taken with the Spitzer space telescope in August 2009, but only recently were the images re-examined by researchers from the Northern Arizona University and the asteroid found to have a coma and tail.

    Not yet numbered


    2011 U1 (P/PanSTARRS)
    Pan-STARRS discovered a 21st magnitude comet on 2011 October 23.45. It is at perihelion at 2.4 AU in June 2012 and has a period of around 8.1 years.  Maik Meyer has located NEAT images of the comet from 2004 February, so the comet should be numbered once a linked orbit is computed.  This may be waiting on additional Spacewatch images.

    SOHO comets of three or more returns

    2007 R5 (S01P/SOHO)
    A Kracht II group comet reported from SOHO C2 imagery by Bo Zhou on September 10.76 is the return of the comet predicted by Sebastian Hoenig, confirming the identity 1999 R1 = 2003 R5. The preliminary time of perihelion is September 11.1, compared to the prediction of September 11.3. Following the precedent of comets 1P, 2P and 27P a suggestion is that the comet should be re-named comet Hoenig. An alternative view is that others have also suggested possible linkages between the SOHO comet groups, eg Rainer Kracht, Brian Marsden and Maik Meyer and that deciding on who should get precedence will be difficult. The CBAT are reluctant to number it because they are not convinced that it is a comet.
    2008 K10 (S02P/SOHO)
    This was a non-group comet discovered in C2 images by Rainer Kracht on 2008 May 31. The original orbit on MPEC 2008-O16 [2008 July 22], gave a retrograde orbit. On the basis of an identification by Rainer Kracht, Brian Marsden has computed a linked orbit with 2004 E2 and 1999 X3, which has a period of 4.2 years and a low inclination. Brian Marsden comments on MPEC 2008-S49 [2008 September 24]
    The identification is by R. Kracht. The observations, all obtained with the LASCO C2 coronagraph, are on MPEC 2006-L20, 2004-M42 and 2008-O16. The The object passed 0.058 AU from the earth on 2000 Jan. 13, 0.032 AU from Mars on 2004 May 19 and 1.17 AU from Jupiter on 2003 Feb. 1.

    1997 J6 (S03P/SOHO)
    In 2009, following the linkage between 2001 D1, 2004 X7 and 2008 S2, Rainer Kracht revisited the archival SOHO C2 images from 1997 and was able to secure a positive identification of the comet.

    Brian Marsden published a linked orbit on MPEC 2009-H56 [2009 April 26] and noted:

    The above computation, using nongravitational parameters A1 = +0.0002, A2 = -0.0002, is based on work by R. Kracht. Despite the poor quality of the SOHO observations, a purely gravitational computation from the four apparitions appears to leave significantly systematic residuals.
    This suggests that the object really is a comet, and should therefore be numbered as such.
    2008 N4 (S04P/SOHO)
    Brian Marsden noted in MPEC 2008-P60 [2008 August 12]:
    R. Kracht suggests that the Kracht-group comet C/2008 N4 is a return of C/2002 S7, principally on the assumption that C/2002 S7 was itself a return of one of C/1996 X5, C/1996 X4 or C/1996 X3 (see MPEC 2006-C49). The derived orbit links C/2002 S7 and C/2008 N4. This gravitational linkage leads to a previous perihelion time of T = 1996 Dec. 6.00, earlier by a few hours than the values for the aforementioned 1996 comets.
    This possibly suggests the presence of non-gravitational effects, which would confirm the cometary nature of these objects. Further work by Brian Marsden confirmed my suggestion and in MPEC 2009-J14 [2009 May 4] he noted:
    Following up on MPEC 2008-P60, R. Kracht has suggested that the correct linkage for C/2002 S7 = C/2008 N4 is with C/1996 X3, on the assumption that the comet was affected by small nongravitational forces (see also MPEC 2009-H56). The nongravitational linkage, with parameters A1 = 0.0000, A2 = +0.0027, is based on Kracht's work.

    2000 C4 (S05P/SOHO)
    On 2011 July 17 Alan Watson reported a Marsden group comet in real time C3 images. Rainer Kracht computed an orbit and then linked the object to 2000 C4 == 2005 W1. A non-gravitational parameter was required to match the perihelion dates.
    2012 A3 (S06P/SOHO)
    On January 19 Alan Watson discovered a fuzzy object with tail in STEREO H1b images from January 17. William Thompson then found images in COR2B. It showed strong forward scattering brightening. Man-To Hui (Cantonese, "Wentao Xu", "Wen-Tao Hsu" in Mandarin) calculated a preliminary parabolic orbit and added astrometric measurements of the COR2B images. Rainer Kracht added STEREO vectors and calculated a short period orbit, which he then linked to 2003 T12 (SOHO), which Brian Marsden had noted might be a short period comet. He suggested that it should also be visible in STEREO images from 2007, and Alan Watson found it in images from November that year. Rainer notes that the comet made an approach to the Earth at 0.18 AU on 2008 January 26.  At the time of closest approach it was around -50 declination and near quadrature. The comet has a period of 4.1 years, with perihelion at 0.6 AU.

    The comet should emerge from solar conjunction in late January, when it might be as bright as 11th magnitude. Ground based astronomers are encouraged to detect the object.  UK observers may be able to find it in mid to late February.

    Note the preliminary designation given by myself (2012 B1) was not issued by the MPC/IAUC.  In the event they decided to ignore the discovery and orbit computation sequence because pre-discovery observations made earlier in January became available, and gave the designation of 2012 B1 to a comet discovered by PanSTARRS on January 25.


    S07P/SOHO = 2002 R1 = 2008 A3 = 2013 Kx
    Peiyuan Sun and Rainer Kracht discovered a Marsden group comet on 2013 May 26. They both linked this to previous returns of a SOHO comet that had been expected to return about June 1, so non-gravitational parameters are required.

    Published by Jonathan Shanklin. Jon Shanklin - jds@ast.cam.ac.uk