BAA Comet Section : Comets discovered in 2011

Updated 2019 November 5

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.

2011 R4 was a return of 1999 R1, with a linked orbit published on MPEC 2015-K01 [2015 May 16]

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

Rainer Kracht suggests that the comet discovered by Rob Matson on February 15 (SOHO-2024) may be a return of either 2005 W1 or 2005 W5, with the latter slightly more likely, but still giving large residuals. Further investigation by Rainer suggested that there is a promising link between the comet and 1995 N5 and 2005 G2, though this required non gravitational forces. This would be the second three apparition linkage of a Marsden comet.

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.

Karl Battams has put together a probable family tree for the fragments.

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

Images of the comet were found in Spacewatch images from 1995 and 2004 (identified by S Nakano) and NEAT images from 2002 (identified by Maik Meyer). The comet was then numbered.

Gareth Williams notes on MPEC 2011-A65 [2011 January 14] that it is probable that this is a short-period comet and that further [astrometric] observations of this comet are desirable.

Further observations confirm the short period orbit, and Hirohisa Sato gives a period of around 6.5 years with perihelion at 1.6 AU in 2010 December.

9 observations received so far suggest a preliminary light curve of m = -3.9 + 5 log d + 28.6 log r, though this is likely to change once the comet is recovered after conjunction.

The comet has brightened rapidly as it approached perihelion and reached 11th magnitude by the equinox. It will brighten a little further, but never becomes well placed for viewing from the UK. Despite the rapid initial brightening, the overall curve has a rather low magnitude parameter.

34 observations received so far suggest a preliminary light curve of m = 9.4 + 5 log d + 4.3 log r

Cometary activity was finally confirmed in 2013, when it was observed from August to October. [MPEC 2013-U85, 2013 October 30]. The comet has a period of 6.6 years.

93 observations received so far suggest a preliminary light curve of m = 6.0 + 5 log d + 6.9 log r

These problems were compounded on May 14, when Hidetaka Sato noted the similarities of the orbit with that of 2002 VQ94 (LINEAR), which had last been observed in October 2010. The comet was at perihelion at 6.8 AU in 2006 February and has a period of around 2500 years.

On IAUC 9209 [2011 May 20] Dan Green notes "The name associated with C/2011 H1 on IAUC 9206 is being abandoned, due to the belated identification of this comet."

10 visual and electronic observations received so far suggest a preliminary light curve of m = 5.1 + 5 log d + 9.5 log r

In May 2012 cometary features were detected by chance by Tomas Vorobjov, with follow-up observations by Sergei Foglia, Luca Buzzi (as described by Luca) and the object was then given a cometary designation.

11 electronic observations received so far give a preliminary light curve of m = -4.8 + 5 log d + [20] log r which suggests that it could be within visual range during 2015 and 2016, however no observations had been reported by 2015 August.

Visual observations began in 2012 March, when the comet was a stellar 14th magnitude, but by May it had developed a coma, and it was around 12th magnitude by mid year. It continued brightening relatively quickly and by September was 10th magnitude. Some observers reported an outburst in August, but this was not apparent in the mean light curve.  

It was recovered after solar conjunction on December 24.3 by Alexander Amorim, when it was 8.1 in his 0.18m reflector.  It soon became clear that the rate of brightening had slowed.  By 2013 February it had reached 5th magnitude.  It continued brightening and by the end of the first week of March had reached 0th magnitude according to observations by Marco Goiato.  The comet was first observed from southern England on March 12.  I observed it from central Cambridge on March 13, when it was around 0th magnitude, with a 15' tail in 8x42B.  Clouds and cold temperatures prevailed for much of March, but on the 28th they parted for a short while at just the right time permitting a view of the comet from a nearby Common.  In 8x42B it was 4.3, with a 1° tail in pa 020.

Nicolas Biver comments that it is one of the dustiest comets observed, with disproportionately high dust compared to its water vapour sublimation rate.

231 observations received to April 30 suggested an aperture corrected preliminary light curve of m = 4.6 + 5 log d + 6.9 log r , however there is some evidence for a change in photometric behaviour when the comet was in solar conjunction between 2012 October 22 and 2012 December 24.  After this period the data is fitted by m = 5.4 + 5 log d + 9.5 log r , with the data prior to this period being about 2 magnitudes brighter than the curve.

Note that a light curve only says how a comet has behaved - there is no guarantee that it will continue to behave in the same way.  

Uwe Pilz generated a simulation of the possible tail appearance. 

From 12 observations 2011 August 1-4. Very uncertain elements, continuing observation very desirable.

The orbit for P/2011 P1 (McNaught) is given for the current standard epoch (2011 August 27.0 TT) rather than the traditional 40-day-epoch closest to the date of perihelion passage. This is due to the close approach (within 0.025 AU) that the comet had with Jupiter in 2010 December. Prior to this encounter (and based on the nominal orbit above), the comet was in an 11.8-year orbit with q = 3.9 AU, Incl = 5 deg and T = 2013 March.

The comet is one of those suspected to have undergone nuclear splitting according to the list of Marcos & Marcos [Dynamically correlated minor bodies in the outer solar system, MNRAS, 474, 838, 2018 February]. They link it to 208P/McMillan.

32 observations received so far suggest a preliminary light curve of m = 5.9 + 5 log d + 10.5 log r

Subsequently S Nakano was able to identify the comet with LINEAR images of asteroid 1998 RS22 and then with 2005 observations by Spacewatch. The comet has a period of 6.5 years.

Only the name Novichonok was originally given to the comet, however the discoverer was clear that it was a team effort with Gerke, and the name was later amended.

Denis Denisenko notes

As usual, there's a whole story behind the new discovery. This comet was caught just 63 (!!!) pixels from the edge of 1330x890 CCD image in 3x3 binning mode in the first night. Upon posting at NEO Confirmation Page most people (including myself) originally thought it to be identical to 111P (whose predicted position was less than 5' away, yet the magnitude was almost identical to the new object). But the direction of motion of the Comet Novichonok was totally different from Comet Helin-Roman-Crockett, and the new object was about twice slower.

Congratulations to Artyom with the first Russian periodic comet since the breakup of USSR! If you remember, two Comets Elenin were discovered on the telescope installed in USA. This time the observation was made in southern Russia, in the Republic of Karachay-Cherkessia in northern Caucasus, not far away from the 6-meter BTA telescope.

The orbit of this object is essentially indeterminate at the present time. It is possible that this is a short-period comet. Among the wide range of possible short-period orbits are orbits that appear similar to P/2006 T1 (Levy). Initial attempts to link the two apparitions have not been successful. Further observations are encouraged.

As seemed possible from the orbit, the object eventually showed cometary characteristics, and was reclassified as a comet with an orbit published on MEPC 2011-Y51 [2011 December 28].

The comet reached around 11th magnitude around the time of perihelion.

19 observations received so far suggest a preliminary light curve of m = -3.9 + 5 log d + 37.8 log r

SOHO observations suggested that the comet reached a peak of around -4, but began fading before perihelion. It showed two tails, which were probably ion (or iron) and dust tails. SDO observations show that it survived perihelion, racing through the solar corona.  It then re-emerged into the SOHO field, brighter but minus the tail, which lagged behind on the other side of the sun.  It was imaged by Terry Lovejoy during daylight on December 17.0, when he estimated it at -1.2.  A visual observation by Alexandre Amorim on December 17.34 put the comet at -2.9. Marco Gioato observed it at 2.8 on December 22.3.  There have been many spectacular images of the tail taken from the Southern Hemisphere.  The comet will  be largely a Southern Hemisphere object.    Details of the SOHO story.

The absolute magnitude of the comet was some 5 magnitudes brighter post-perihelion than it was pre-perihelion. A likely explanation is that a part of the comet's surface was inactive prior to perihelion, and that as the nucleus rotated through the solar atmosphere the inert surface was eroded away, exposing fresh material. It is possible that as the comet recedes from the Sun, parts of the fresh surface will choke off, resulting in a relatively quick fading.

Terry provided the following background on the comets-ml

Anyway to the discovery of C/2011 W3, it was the first comet I have found with my new equipment setup. I now use a C8 Schmidt-Cassegrain scope working at f2.1 with a QHY9 CCD camera. This gives me a field of view of a 4.5 square degrees which although only 1/8th of that of my previous DSLR camera, more than makes up for this in extra sensitivity. As a result I can cover the same amount of sky to perhaps a magnitude deeper. Despite this it has been over 4 years since my last discovery and I do hope the next one comes a lot sooner!

The actually discovery images of W3 were made on November 27.7UT, 2011 (Wednesday morning local time). On that morning I imaged some 200 different fields with 3 images each, taking about 2 hours to fully process. After processing, I began searching and on one set of images I noticed a rapidly moving fuzzy object. As I was unsure this was real, I noted the positions and wrote a brief comment "Possible reflection" before proceedind to search more images. The next night I decided to investigate further the suspect since its position, shape and motion didn't appear consistent with an optical reflection and for this reason I decided to make a followup observation.

On November 29.7 UT I began an imaging sequence around the estimated position of the object. However, if the object was real it was travelling very rapidly at 3 degrees per day so any uncertainty in the direction and speed would mean the estimated position could be in error by a couple of degrees. Furthermore cloud and haze hampered imaging that morning. Nonetheless, I was able to capture 6 images that showed a faint but definite fuzzy object near the expected position. Additionally the fuzzy object was consistent in both motion and appearance to the object found 2 mornings earlier. At this point I sent out a request for independent confirmation to a number of trusted observers.

On November 30, all recovery attempts were thwarted for many reasons including weather and insufficient limiting magnitude. Interestingly though, Michael Mattiazzo made a comment that he felt the observed positions were similiar to that of a Kreutz sungrazer. Then, finally, on December 1 I recieved an email from Alan Gilmore stating that he and Pam Kilmartin had successfully imaged the comet with the 1 metre telescope at Mt John Observatory. A few hours later I also managed to get some followup images. The object was then published on the NEO confirmation page before being susequently officially announced in CBET 2930/2931 on December 2.

Although a new orbit is being published, the December 19 STEREO observations were within about 1' of the previously-published orbit. The new observations were weighted 0.1 in the above orbit. Resolution of the issues surrounding the STEREO astrometry will probably have to await the acquisition of further ground-based astrometry.

C/2011 W3 remains a difficult target for astrometry, as evidenced by the poor consistency of the latest observations. McNaught writes: "Star fit RMS 0.3", but measures are much less reliable than that. The positions are of the tip of the "spine" which lies pretty much on the front edge of the parabolic hood. It is rather less well defined than on Dec 23. For this reason I cannot be sure just how closely I am measuring the same point as on Dec 23."

A presentation "A Multiwavelength Investigation of the Remains of the Sungrazing Comet Lovejoy (C/2011 W3)", was given by Matthew Knight. You can fread the abstract (PDF). It was interesting to see images of the comet's remains obtained by Hubble, Swift and Spitzer telescope, showing the absence of the nucleus and lots of dust.

12 observations received to January 4 suggest a preliminary light curve of m = 10.8 + 5 log d + 15.8 log r