BAA Comet Section : Not yet designated objects

Updated 2024 June 1

Possible comets
  • P/LINEAR = 2000 XO8
  • A/Lemmon = 2015 EG
  • (264357) = A/LINEAR = 2000 AZ93
  • A/Lemmon = 2008 BJ22
  • A/Lemmon = 2010 DJ10
  • A/Palomar = 2012 KA51
  • A/PanSTARRS = 2017 DJ
  • 2017 GZ8 [A/Mt Lemmon]
  • A/PanSTARRS = 2017 MC9
  • A/PanSTARRS = 2017 PY24
  • A/PanSTARRS = 2017 YL4
  • A/LINEAR = 2005 YB210
  • A/Palomar = 2010 LN135
  • A/WISE = 2010 LH15
  • A/PanSTARRS = 2018 BJ11
  • A/Lemmon = 2023 JN16

    Numbered asteroids
  • (596) Scheila
  • (1474) Beira
  • (3200) Phaethon
  • (3552) Don Quixote
  • (6478) Gault
  • (7341) 1991 VK
  • (62412) 2000 SY178 [P/LINEAR]
  • (65803) Didymos
  • (248590) 2006 CS

    SOHO Comets
  • S04P/SOHO (2008 N4)
  • S05P/SOHO (2000 C4 = 2011 ??)
  • S06P/SOHO (2003 T12 = 2012 A3)
  • S07P/SOHO (2002 R1 = 2008 A3)

    Numbered comets
  • Comets 1 - 99
  • Comets 100 - 199
  • Comets 200 - 299
  • Comets 300 - 399
  • Comets 400 - 499
  • 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.

    Probable/Possible comets

    Sam Deen has identified several objects that seem to show clear evidence of a cometary nature, but which have not yet been recognised by the MPC.  These were described in a post on the comets-ml on 2021 April 7, with additional objects described on May 23, September 29 and 2022 December 15. In the following entries "I" refers to Sam Deen.
    A/Palomar = 2012 KA51
    2012 KA51 was discovered on 2012/05/22 by the Palomar Transient Factory (PTF) and observed for only a week without being recovered. I found many more unmeasured observations from PANSTARRS which showed it to be a highly eccentric object with a perihelion of 4.896 au and an aphelion of 959 au. in all of these observations it appears noticeably elongated (or too faint to make out features anyway). Furthermore, investigating the original PTF images shows it as rather noticeably fuzzy.
    A/PanSTARRS = 2017 DJ
    To quickly preface, this one might not be a comet. The evidence for activity is suspect, but looks strong enough for me to include anyway. 2017 DJ was discovered on 2017/02/17 by PANSTARRS and observed for just 2 days without recovery. I extended the arc to 21 days, enough to calculate a rudimentary orbit with P=5.84 years and q=1.76 au. Although there are no accessible observations near its perihelion (the last high-quality observation is February 21 (r = 1.84)) the observations do show it being visibly hazier than surrounding stars. Luckily it shouldn't remain ambiguous for too long, as 2017 DJ will be returning in early 2023 with some slightly more favorable geometry to allow us to observe it nearer to perihelion.
    A/PanSTARRS = 2017 GZ8

    A/PanSTARRS = 2017 MC9
    2017 MC9 was discovered on 2017/06/22 by PANSTARRS and observed for 11 days without being recovered. I found a very extensive set of W84 observations going into September, still not published, which give a robust orbit with P=6.23 years and q=1.61 au. It appears reliably fuzzy with a tail pointing west and then northwest on 2017/07/02 (r=1.61), 2017/07/03 (r=1.61), 2017/07/17 (r=1.61), and 2017/08/25 (r=1.67), but not on 2017/09/02 (r=1.69). None of this is too surprising, as running its orbit back shows that it had a much higher perihelion distance of 2.1 au until the early 1800s, and then ~1.85 until the 1940s. Its 2017 perihelion was actually its closest yet to the Sun, and it looks like as close as it's going to get for a while as it oscillates between 1.6 and 1.7 au for the next couple centuries.
    A/PanSTARRS = 2017 PY24
    2017 PY24 was discovered on 2017-08-07 by PANSTARRS and observed for about a month, the last (previously published) observation from 4 days before perihelion. I found a number of observations purposefully made of the comet, but never reported for some reason, between December 2017 and January 2018, in all of which it is an extremely clear-cut case of a comet, with the peculiarity that its tail seems consistently separated from the comet head itself. With a period of 72 years, it's a definite Halley-type comet.
    A/PanSTARRS = 2017 YL4
    2017 YL4 was discovered on 2017-12-24 by PANSTARRS and observed for just two days before being lost. I was recently able to find many more observations showing it as very obviously as a long period comet (P = 1900 yr). On 2018/02/11, the object appeared obviously cometary, with a decently condensed coma with a FWHM of around 1.0 arcsecond (the seeing isn't reported but I would visually estimate 0.4 arcseconds). The tail is 8 arcseconds long and mildly curved, stretching south at a PA of around 155-165.
    A/LINEAR = 2005 YB210
    This asteroid was discovered by LINEAR about two years after perihelion, with prediscovery observations found from 2004. It was recovered in 2019 by PanSTARRS. Sam found additional images from 2013, and from 2019. The magnitude of the object is quite variable between 19 and 23, suggestive of cometary outbursts, though none of the images shows tail or coma.
    A/Lemmon = 2008 BJ22
    This asteroid was discovered by the Mt Lemmon Survey in images taken with the 1.5m reflector on 2008 January 31.38. Until Sam Deen chased down further positions it was regarded as a normal Main-belt asteroid. The additional observations showed a distinct tail in 2008 Subaru, 2009 PTF and 2013 DECam images. Sam suggests that the asteroid completely disintegrated in 2008, leaving only the debris trail. The disintegration could be due to an impact or YORP spin-up.
    A/Palomar = 2010 LN135
    This object was discovered by the Palomar (Zwicky) Transient Factory on 2010 June 4.29 at 21st magnitude. It is in a near parabolic orbit, with perihelion at 1.7 au in 2011 May, when it might have reached 16th magnitude. Curiously no observations were made after 2010 August 15. PanSTARRS images taken on that date show a coma and possible tail. Although the PTF observers recognised it as a comet at the time, it was never acknowledged by the MPC. When the MPC published an orbit [MPEC 2024-H77, 2024 April 27] there were additional observations from September and October made by the Catalina Sky Survey and it was given a formal A/ designation.
    A/Lemmon = 2010 DJ10
    This asteroid was discovered by the Mt Lemmon Survey in images taken with the 1.5m reflector on 2010 February 16.39. Until Sam Deen chased down further positions it was regarded as a Main-belt Mars-crossing asteroid. The additional observations show that it is in a Jupiter and Saturn crossing orbit with perihelion at 2.8 au and period of 17 years.
    A/PanSTARRS = 2018 BJ11
    This asteroid was discovered by PanSTARRS on 2018 January 20.33 at 22nd magnitude. There were pre-discovery PanSTARRS images from 2017 November 20 and 2018 January 11. The object was followed until February 9. It was at perihelion in 2015 November at 3.2 au and has a period of 8.5 years. In 2023 June K Ly found a DECam image from 2018 March 8 that shows a diffuse coma. It can approach Jupiter to within 0.4 au.
    A/Lemmon = 2023 JN16
    This asteroid was discovered at 19th magnitude by the Mt Lemmon Survey in images taken with the 1.5m reflector on 2023 May 10.23. The brightness and lack of pre-discovery observations was suggested by Peter VanWylen to indicate a possible main belt comet. Sam Deen, Arndt Schnabel and K Ly made follow-up observations and detected clear signs of cometary activity on June 16. It was at perihelion in 2020 July at 2.3 au and has a period of 4.4 years in a low eccentricity orbit, which gives no particularly close planetary approaches.  It returns to perihelion in 2024 December.

    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.

    (1474) Beira
    Alan Hale noted on the comets-ml [2021 August 27] that a paper by Busarev et al reported possible detection of ice sublimation from the asteroid whilst near perihelion in 2012. So far he had not detected any evidence of a coma or tail at the 2021 return, when perihelion is in December. Sam Deen then noted that it is in a Kozai resonance with Jupiter and that the perihelion distance has been slowly reducing for the last few millenia. It is currently near its minimum of 1.4 au.
    (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. Qicheng Zhang et al in a 2023 paper suggest that the cometary like activity is due to Sodium D emission, a feature shared with 322P/SOHO and 323P/SOHO.

    (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 in 2014 were the images re-examined by researchers from the Northern Arizona University and the asteroid found to have a coma and tail.  Further images taken in 2018 March with the 4.1m Southern Astrophysical Research Telescope at visible wavelengths also show cometary features. 
    (6478) Gault
    Asteroid (6478) Gault was discovered in 1988 by Carolyn & Gene Shoemaker and is named after Donald Gault who was an expert in impact cratering. It is a main-belt asteroid of the Phocaea group and has a period of 3.5 years with perihelion at 1.86 au. On 2019 January 5, observations by ATLAS showed that it had a tail or trail, which was then found in previous images back to 2018 December 8. The imagery is consistent with activity having started in early 2018 November, probably in a collision.  The (25) Phocaea group of asteroids are thought to be the remains of a major collision that took place 2.2 billion years ago.  A second tail was discovered on January 26, effectively ruling out the impact hypothesis.  NASA/GFC suggest that the asteroid was spun up by the YORP effect and is now rotating too fast to retain surface material, which is shed in the tails.
    (7341) 1991 VK
    Discovered by Eleanor Helin and Ken Lawrence at Palomar on 1991 November 1, this Apollo asteroid is currently on the PCCP as a possible comet candidate.
    (62412) 2000 SY178 [P/LINEAR]
    S. S. Sheppard, Carnegie Institution for Science, Washington and C. A. Trujillo, Gemini Observatory, reported the detection of a faint tail to the main-belt minor planet (62412) 2000 SY178 in three 400-s VR-band CCD exposures taken with the Blanco 4-m telescope at Cerro Tololo on 2014 March 28.  The faint tail was observed at position angle about 295 degrees and extended about 1' from the nucleus.  Follow-up observations at the Magellan telescope on May 1 and 2 confirmed the activity of (62412). [IAUC 9272, 2014 October 30] 

    The asteroid has a period of 5.6 years and was at perihelion at 2.9 au in 2013 March. It was discovered by LINEAR on 2000 September 28.

    The SPA ENB provided additional information: A new active asteroid, numbered 62412, has been discovered in the main asteroid belt between Mars and Jupiter. It is the first comet-like object seen in the Hygiea family of asteroids. Active asteroids are a newly recognized phenomenon and 62412 is only the 13th known active asteroid in the main asteroid belt. It is estimated that there may be about 100 of them in the main asteroid belt. Active asteroids have stable orbits between Mars and Jupiter like other asteroids; unlike other asteroids, however, they sometimes have the appearance of comets, when dust or gas is ejected from their surfaces, creating a sporadic tail effect. Astronomers recently discovered a tail on 62412, an object which had been known as an ordinary asteroid for over a decade. The reasons for the loss of material and the formation of a tail in active asteroids are unknown, although there are several theories such as recent impacts or sublimation from solid to gas of exposed ices.

    In the past, asteroids were thought to be mostly unchanging objects, but an improved ability to observe them has allowed scientists to discover tails and comas, the latter being like the thin envelopes of atmosphere surrounding comets' nuclei. Discoveries such as this one can help researchers to determine the processes that cause some asteroids to become active. They found that 62412 has a very fast rotation that may shift surface material, some of which may leave the surface and form the comet-like appearance. The tail may be created directly from material ejected from the fast-rotating body, or from ice within it subliming into water vapour after being freshly exposed on the surface. The density of 62412 has been found to be typical of primitive asteroids and not consistent with the much lower densities comets.

    (65803) Didymos Didymos is a binary asteroid. The secondary component, Dimorphos, was targeted by the NASA DART interceptor mission on 2022 September 27. The asteroid brightened dramatically on impact, and susbsequently developed multiple tails.
    (248590) = 2006 CS This is the parent body of the beta Toucanid meteor stream, which was active in 2020, 2021 and 2024, but not obviously in 2022 or 2023. It is presumed to be a dormant Jupiter family comet. [CBET 5372, 2024 March 21] JPL class it as an Apollo NEO and it was last at perihelion in 2021 March. It has a period of 5.0 years and perihelion at 0.9 au. It will be 0.16 au from the Earth on 2026 March 20, but for a really close approach you will have to wait until 2116. It was discovered by the Siding Spring Survey on 2006 February 1.

    Not numbered, but seen at two returns

    P/LINEAR = 2000 XO8
    An asteroid discovered by LINEAR on 2000 December 1.38 was found to show a coma and tail in images taken by the Deep Ecliptic Patrol of the Southern Sky (DEEP-South) team, in CCD images taken with the Korea Microlensing Telescope Network (KMTNet) 1.6-m f/3.22 telescope at Siding Spring Observatory (SSO) in Australia in October and the same type of telescope installed at Cerro Tololo Interamerican Observatory (CTIO) in Chile in November.  [CBET 4460, 2017 December 13]. The comet was at perihelion at 1.5 au in 2017 October and was previously classed as an Outer Main-belt asteroid.  It has a Jupiter MOID of 0.016 au, and will pass 0.23 au from the planet in 2042.  This will be followed by an approach to the Earth at 0.33 au in 2051.
    A/Lemmon = 2015 EG
    This Aten type asteroid was discovered by the Mt Lemmon Survey in images taken with the 1.5m reflector on 2015 March 9.33. At the close approach in 2019 March, radar measurements showed that it was experiencing non-gravitational forces. [CBET 4786, 2020 May 30]. The asteroid is an NEO and PHO. The next perihelion is at 0.6 au in 2020 July and it has the exceptionally short period of 0.8 years.  The orbit has an Earth MOID of 0.003 au and the object makes frequent close passes to both Earth and Venus. The most recent close approach to the Earth was 0.0030 au on 2019 March 4 when it also passed 0.0031 au from the Moon, and to Venus was 0.05 au on 2018 January 21. The next Earth approach will be to 0.036 au on 2023 March 4.
    (264357) = A/LINEAR = 2000 AZ93
    This Aten type asteroid was discovered by LINEAR in images taken on 2000 January 7.08. At the close approach in 2019 December, radar measurements showed that it was experiencing non-gravitational forces. [CBET 4787, 2020 May 30]. The asteroid is an NEO and PHO. The most recent perihelion was at 0.5 au in 2020 May and it has the exceptionally short period of 0.65 years.  The orbit has an Earth MOID of 0.022 au and the object makes frequent close passes to the Earth, Venus and Mercury. The most recent close approach to the Earth was 0.0057 au on 2019 December 16, and to Mercury was 0.07 au on 2017 February 15.
    A/WISE = 2010 LH15 = 2010 TJ 175
    The WISE spacecraft discovered an object on 2010 June 3.50 and followed it until June 9. The Catalina Sky Survey discovered an object on 2010 October 28.22, which received a designation, though pre-discovery observations by the Survey had previously been published. There are NEAT observations from 2001 and subsequent observations to 2019. It is classed as a Main Belt Asteroid, with a period of 4.5 years and is next at perihelion at 1.8 au in 2024 March. A paper by Colin Chandler et al announced that it showed cometary activity on 2019 September 30 in a DECam image. Further investigation showed cometary activity in 2010, when it was near perihelion. They suggest that it may again show activity from late 2023.

    SOHO comets of three or more returns

    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.
    S06P/SOHO = 2003 T12 = 2012 A3 = 2016 Dx
    On 2012 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 IAU decided to ignore the discovery and orbit computation sequence, which would give a designation of 2012 B1 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.

    The comet was recovered by Worachate Boonplod in STEREO-A images from 2016 February 20.  A linked orbit was published on March 12 [MPEC 2016-E131]

    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.
    S08P/SOHO = 2008 Y12 = 2014 K3
    A non-group comet was discovered in C2 images by Rainer Kracht on 2008 December 23.  In 2012, further images were found in STEREO HI-1A frames from December 21 and 22, which lead to an improved orbit.  Michal Kusiak notes that there is a strong similarity to the orbit of the Southern Delta Aquarids, and Rainer Kracht suggested that the comet may have a short period.

    A non-group SOHO comet discovered in C2 images by Zhijian Xu on 2014 May 17 was quickly linked to 2008 Y12 by Michal Kusiak and the orbit confirmed by Reiner Kracht. A linked orbit by Gareth Williams was published on MPEC 2014-K37 on May 24. The comet has a period of 5.4 years and perihelion 0.07 au.

    Published by Jonathan Shanklin. Jon Shanklin -