Updated 2023 December 2
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.
2000 saw comet 2P/Encke's 58th observed return to perihelion since its discovery by Mechain in 1786. The orbit is quite stable, and with a period of 3.3 years apparitions repeat on a 10 year cycle. There is some evidence for a secular fading, however this is not shown in BAA data over the last 50 years. Another suggestion is that Encke has two active regions, an old one with declining activity, which operates prior to perihelion and a recently activated one present after perihelion. The comet is the progenitor of the Taurid meteor complex and may be associated with several Apollo asteroids.
Observations received in 1997 (15) give a preliminary light curve of 11.8 + 5 log d + 18.6 log r
Observations in ICQ format, last observation 1997 July 7, updated 1997 July 28 .
A few observers spotted the comet in early 2000 August, estimating it at around 11th mag. Pepe Manteca imaged the comet on August 10 and August 14. The comet was visible in the SOHO C3 coronagraph, but was fainter than expected and was only 8.8 on September 7.1. It suddenly brightened on September 14 around 15:00 to 6.5.
2003 The comet was picked up visually at the 2003 return in October, however it was initially very diffuse and significantly fainter than expected. In the Northumberland 0.30-m refractor x230 I estimated it 12.9 on October 24.89 with a 0.8', DC1 coma. It was half a magnitude brighter a couple of nights later. Following reports on the comet mailing list that it was significantly brighter in binoculars, I visited a dark sky site on October 27.94 and found it at 9.9 in 20x80B with a 4.5' DC3 coma. It was a very easy object in 25x100B. On November 16.81 I estimated it at 7.7 in 20x80B, with a 10' diameter DC2 coma. On November 26.73 it was 6.8 in 10x50B with a 13' DC3 coma. Many observers comment on the pronounced fan of material coming from a stellar nucleus. Most observers lost it in early December, but Juan José González Suárez was able to view it from a mountain location on December 24.28, estimating it as a stellar object of approx 4.7 in 25x1000B.
For the 2003 return 52 observations give a preliminary corrected light curve of 10.7 + 5 log d + 12.3 log r.
L. M. Woodney, University of Central Florida; and T. C. Owen and Y. R. Fernandez, University of Hawaii, report the detection of HCN from comet 2P/Encke. The HCN J(4-3) transition was observed during Nov 9-11 UT at the James Clerk Maxwell Telescope. The line had a FWHM of 1.4 km/s and an integrated line strength of 0.057 +/- 0.011 K km/s. Assuming a rotational temperature of 43 K, and using a Haser model, a production rate of Q(HCN) = 9.8 x 10**23 molecules/s was derived. [IAUC 8239, 2003 November 17]
F. Bensch, Harvard Smithsonian Center for Astrophysics (CfA); E. Bergin, University of Michigan; and G. Melnick, CfA, write: "We have monitored the 1(10)-1(01) emission of water vapor at 556.936 GHz toward comet 2P using the Submillimeter Wave Astronomy Satellite (SWAS). Between Nov. 7.04 and 15.21 UT, the line- integrated antenna temperature within the 3'.2 x 4'.5 elliptical SWAS beam varied between I < 0.252 (3-sigma upper limit for observations on Nov. 7.04-7.99) and I = 0.98 K km/s (Nov. 12.03- 12.99). The average line-integrated intensity for this period is I = 0.55 +/- 0.03 K km/s. The water-production rate, Q(H_2O), is derived using a spherical outflow model (Haser model) with a water photo-destruction rate of 1.366 x 10**-5 s**-1 and an assumed ortho-para ratio of 3. The uncertainty in the resulting Q(H_2O) is governed by the finite S/N ratio of the observations and the uncertainty in the electron abundance in the coma. (In addition to infrared fluorescence and H_2O-H_2O collisions, H_2O-electron collisions provide a significant contribution to the 1(10)-1(01) line excitation; our modeling of the electron abundance uses the same parameterization as Biver et al. 1999, A.J. 118, 1850). For observations made between Nov. 9.06 and 9.96 (I = 0.53 +/- 0.07 K km/s), we derive Q(H_2O) = (2.9 +/- 0.4) x 10**27 s**-1 for an electron abundance similar to those derived by in-situ measurements in the coma of 1P/Halley, and Q(H_2O) = (4.0 +/- 0.5) x 10**27 s**-1 for an electron abundance reduced by a factor of 0.2. Previous studies of this transition toward several other comets by SWAS and by the (sub)millimeter-wavelength satellite Odin have indicated that the electron density in cometary comae might be smaller by a factor of about 0.2, compared to the electron density in 1P/Halley (Biver, private communication, based on data from Lecacheux et al. 2003, A.Ap. 402, L55)." [IAUC 8249, 2003 December 4]
Observations in ICQ format, last observation 2003 December 24, updated 2003 December 29.
Comet 2P/Encke in 2007 2P/Encke put on a brief showing in the UK evening sky in late March and early April just before perihelion, when it was a binocular object in Pisces and Aries. After perihelion it was visible passing through the SOHO LASCO field and that of its successor, STEREO. STEREO imaged a disconnection event in the ion tail, and a NASA press release was issued in October.
This was comet Encke's 60th observed return to perihelion since its discovery by Mechain in 1786. This year the comet was briefly seen from the Northern Hemisphere prior to perihelion, with rather better views from the Southern Hemisphere after perihelion, when the comet is often brighter.
Martin Mobberley made an early image of the comet at its 2007 return, imaging it on 2006 December 9.81 when it was still only around 18th magnitude.
5 observations received give an uncorrected preliminary light curve of m = 10.7 + 5 log d + 8.3 log r
Observations in ICQ format, last observation 2007 April 13, updated 2007 April 16.Comet 2P/Encke in 2010 This is comet 2P/Encke's 61st observed return to perihelion since its discovery by Mechain in 1786. The orbit is quite stable, and with a period of 3.3 years apparitions repeat on a 10-year cycle. This year it has a poor elongation prior to perihelion, but it will be visible passing through the SOHO LASCO field and that of its successors, the twin STEREO satellites in late July and early August. After perihelion the comet becomes visible from the Southern Hemisphere in mid August as a fading binocular object, and can be followed throughout September. BAA Members have been observing the comet for over 50 years and there is little evidence for a secular fading, although the comet is often brighter post perihelion than it is before. The comet is the progenitor of the Taurid meteor complex and may be associated with several Apollo asteroids.
The comet was first picked up in the SOHO C3 field on August 4. It became visible to Southern Hemisphere observers mid-month.
34 observations received give an uncorrected preliminary light curve of m = 10.2 + 5 log d + 6.4 log r
Observations in ICQ format, last observation 2010 September 13, updated 2010 November 3.Comet 2P/Encke in 2013 This year sees comet 2P/Encke's 62nd observed return to perihelion since its discovery by Mechain in 1786. The orbit is quite stable, and with a period of 3.3 years apparitions repeat on a 10-year cycle. This year the comet is well seen from the Northern Hemisphere prior to perihelion, which is in late November. The comet brightened rapidly during October rising from about 11th magnitude at the beginning of the month to 7th at the end. Its brightness didn't change much during the first half of November, though it became more condensed. It is now poorly placed for observation. Observations from the
31 electronic and visual observations received give an uncorrected preliminary light curve of m = 11.0 + 5 log d + 8.7 log r
A 2021 paper by Zdenek Sekanina reviews the evolution of the non-gravitational motion of the comet. The comet had been arriving at perihelion earlier than predicted by purely gravitational motion, but the amount had been decreasing. Recent work by Nakano and Rudenko show that it is now arriving at perihelion later than predicted. This had been forecast to occur on the basis of a nuclear precession model. He notes that Kamel, in a 1991 paper suggested that apparent secular fading since 1840 (when it was brightest three weeks before perihelion) can be explained by an assymmetric light curve, with the timing of the asymmetry linked to the precession of the nucleus and which gives a shift of 25 days in peak brightness over 150 years. He suggests that there is currently no (or little) asymmetry in the light curve. If the forecasts are correct the asymmetry should begin to grow over coming returns. No significant secular trend is shown in BAA data since 1937, though there is slight fading of the absolute magnitude. Recent observations do not show any significant asymmetry. During this time the non-gravitational acceleration has declined from a quarter of what it was at the peak in 1820, to virtually zero.
Comet 2P/Encke in 2023 The comet passed through the SOHO C3 field between 2023 October 24 and November 12, fading rapidly as it retreated from perihelion.
The 2006 return was very similar to the 1991 return, when it reached 10th magnitude. It behaved much as predicted and was at its brightest in early November 2006 at just brighter than 10th magnitude. By mid January 2007 it was around 12th magnitude and had only faded a little further by April.
It was not well placed when at its brightest during the 2014 apparition, but a few observations were made as it was fading. Electronic images in 2014 November showed a distinct tail.
126 observations received at the 2006 return give an uncorrected preliminary light curve of m = 9.4 + 5 log d + 7.2 log r
8 observations received at the 2014 return give an uncorrected preliminary light curve of m = 9.7 + 5 log d + 8.5 log r
Observations in ICQ format, last observation 2007 April 5, updated 2007 April 16.
The comet was recovered at its 2008 apparition in late April by observers at Lowell Observatory's Anderson Mesa Station and Kachina Observatory, Flagstaff. It was around 19th magnitude. It appears to have undergone something of an outburst around the time of perihelion
The comet appears to have a rapid switch on as it approaches perihelion, followed by a linear light curve. It may show secular trends in the magnitude parameter and the 2021 return may shed some light on their nature, although so far the observations are quite scattered. It was reported as being visible in SWAN images in early November 2021, although by then it was fading. This suggests that it is perhaps a gassy comet.
Observations in ICQ format, last observation 2002 August 13, updated 2002 November 6.
Overall, observations made between 1939 and 2015 are not particularly consistent. They give a mean H10 magnitude of 10.7. There is some evidence for a linear light curve and this is seen during the 2021 return.
The comet was recovered in April 2007, with delta T of +0.13 days compared to the prediction on MPC 54167. Observations in early November suggested that it had reached 14th magnitude.
P. Jenniskens, Ames Research Center, supplied a prediction (Jenniskens and Lyytinen 2000, WGN, submitted) of enhanced activity in 2000 of the meteor stream associated with comet 8P/Tuttle. Notable Ursid outbursts near the time of 8P's aphelion occurred in 1945 and 1986. Maximum activity is anticipated around Dec. 22.31 UT from material ejected from the comet in 1405. Ejections in 1392 and 1378 could expand this activity over an interval of 4-5 hours. [IAUC 7455, 2000 December 18] P. Jenniskens, Ames Research Center, reports that preliminary results show that there was an enhancement of Ursid meteors visible between Dec. 22.2 and 22.4 UT, including several brighter than mag 1, with a peak (ZHR > 50) near the predicted time of Dec. 22.31 [IAUC 7548, 2000 December 23]
Observations by D. Schleicher, Lowell Observatory; and L. Woodney, California State University, San Bernardino, using CN narrowband imaging on Dec. 14 with the Hall 1.1-m telescope at Lowell Observatory show three radial arcs. If these are from the same jet, it implies a rotation period of 4.9 - 5.0 hours.
216 observations received give a preliminary light curve of m = 6.8 + 5 log d + 0.0429 abs(t-T-27.1)
Observations in ICQ format, last observation 2008 March, updated 2008 April.
It was reported as being visible in SWAN images in early November 2021, although by then it was fading. This suggests that it is perhaps a gassy comet.
I was finally able to observe the comet on 2005 April 4.9, finding it an easy object in the N'land refractor. It was mag 11.7, DC4 and diameter 0.7'. Observations in late May were putting it at around 10.5 - 11th magnitude.
Comet 9P/Tempel was the target for the Deep Impact mission in 2005 and observations were requested. Observations from the HST and the onboard Deep Impact camera show what appear to be minor outbursts of the comet during 2005 June. These are promoted as major events by the NASA Deep Impact site, although they are of short duration (dissipating in less than 12 hours) and are of small size (about 2000 km). Interestingly stars passing through the field appear to brighten during the event shown by the DI camera. Following the impact, there was no obvious increase in visual magnitude, however the coma did become more condensed. The Stardust-NExT spacecraft encountered 9P/Tempel at 03:40 UT on 2011 February 15. It returned images showing the effects of the Deep Impact hit on the comet in 2005 July.
192 observations give a preliminary light curve of m = 6.8 + 5 log d + 23.1 log r. The H10 magnitude is 9.4. The light curve in 2005 was very similar to those in 1983 and 1994 and taking all together gives an aperture corrected equation of m = 5.7 + 5 log d + 21.9 log r
30 observations in 2016 give a preliminary light curve of m = 3.6 + 5 log d + 36.8 log r.
2005 Observations in ICQ format, 47 observations, updated 2005 June 1.
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 2015 T3 (P/PanSTARRS).
Traditionally the light curve is regarded as highly asymmetric with a late turn on. There is a rapid rise in brightness as perihelion approaches, which continues more slowly for a couple more weeks after perihelion, followed by a slow decline until activity switches off. An alternative view is that the light curve is linear with a peak about a month after perihelion.
With a 5.5 year period alternate returns are favourable and the 2010 return is one of them.
1999 David Strange obtained an image of the comet on July 10. Jose Carvajal estimated it at 10.6 in 32cm L on August 5.9, but I was unable to see it with 20cm R on the same night. On Aug 10.9 Andrew Pearce and I observed it with 14x100B from just outside Penzance, Cornwall, my estimate was 8.7 (HS) and Andrew made it a little fainter. Back in Cambridge it was a very difficult object in the 0.20-m refractor, though it was observed during the IWCA. Andrew Pearce now back in Australia reported that the comet has faded to near 10th mag at the end of August. It faded very slowly and it was still 12th mag in December. 2010 Deep images of 10P/Tempel showed a dust trail in the plane of the comet's orbit. Francois Kugel and C Rinner obtained a mosaic on July 14. Further images on July 24 show the trail extending over 20 degrees from the nucleus. 2015 So far sixteen electronic and visual observations have been received and these suggest that the comet is fainter than expected, being only 17th magnitude in June, brightening to 14th by the end of August and 10th magnitude by December.
111 observations received at the 1999 return give an uncorrected preliminary light curve of m = 10.4 + 5 log d + 0.0295 abs(t-T-18.1) or 6.1 + 5 log d + 29.3 log r.
Observations in ICQ format , last observation 2000 January 30, updated 2000 August 16.
73 observations received at the 2010 return give an uncorrected preliminary light curve of m = 9.4 + 5 log d + 0.0152 abs(t-T-28)
Observations in ICQ format , last observation 2010 October 28, updated 2010 November 3.
16 observations received at the 2015 return give an uncorrected preliminary
light curve of
m = 2.6 + 5 log d + 42.6 log r though a linear light curve
with the comet brightest 16 days after perihelion fits the data better
JJ Gonzalez made a visual observation of the comet at the 2020 return, estimating it at 11th magnitude on 2020 December 8.8. Following a Jupiter encounter in 2018 the perihelion distance is now its smallest (1.4 au) since 1908, having been lost following Jupiter encounters until 2001. It will decrease further to 1.2 au after another encounter in 2030.
The comet was recovered by the 4.3 m Lowell Discovery Telescope on 2020 June 10.40 at 23rd magnitude. On 2023 July 20 it suddenly brightened from 16th to 11th magnitude. Measurements by Nick James suggest an outflow velocity of 200 m/s in a single impulsive event. Nick has written a preliminary report on the event. Further large events occurred on October 5, 31, November 14 and 30. Occasional outbursts should be no surprise as most comets are likely to experience stochastic fragmentation events. It is rather like watching icebergs calve off a glacier. It is however interesting that the morphology of the coma in the October events developed in a similar way to the July event; this may suggest that they occured in the same area of the comet nucleus. The mid November event seems to be different, with a circular coma developing and a faster expansion rate, which Nick James estimates at 350 m/s. I am now inclining to the alternative view, proposed by Richard Miles (though not in these words), that the comet farts (passes wind) to relieve the build-up of gas below its crust. On November 15 it was a very easy object in the Northumberland refractor and also visible in 25x100B. It showed a very small coma diameter of around 0.5', DC8 and about mag 9.5. It seems that this latest event has triggered greater activity on the comet, with images showing jets and tail development. The coma steadily become more diffuse until the next event at the end of the month.
The likely peak brightness is difficult to predict, as this will depend on whether 'outbursts' continue and with what frequency. It could become a naked eye object, possibly reaching 2nd magnitude, in the northern spring and will be observable from the UK until mid April.
Alan Hale recovered the comet on 2023 August 24 and provides the following account
I first began searching for 13P in October 2022, utilizing the telescopes of the Las Cumbres Observatory (LCO) global network, where I’m a member of the Global Sky Partners. My attempts were all unsuccessful up through the time the comet entered conjunction with the sun earlier this year, then beginning in mid-June 2023 following its emergence into the morning sky I have been making additional attempts on roughly a biweekly basis.In 2024 the comet will be a telescopic object in the evening sky during the first part of 2024, becoming poorly placed. Circumstances improve during June and the comet will be nearing its brightest by the solstice, with the comet visible in the late evening. It reaches its greatest northern declination at the end of the month and slowly fades as it moves southwards. UK observers will lose it in mid September. It passes some 6° from the Pleiades in April, though the comet may only be 10th magnitude at the time. Although there is a pass close to M36 in May, the solar elongation is poor. The fading comet passes by the galaxy M64 and the globular cluster M53 over the period August 24 to September 2.
On August 24.7 UT I took two 10-minute exposures with one of the 1.0-meter telescopes at LCO-Siding Spring. When examining these images I spotted a faint moving object a little over 5 arcminutes from the MPC’s ephemeris prediction, along the line of variation at roughly Delta_T ~ -0.73 day from that prediction. Armed with this information, I successfully detected images of the comet on exposures taken on August 13.1 UT from LCO-SAAO; these images are very weak, and I’m not surprised I failed to notice them at the time. Since then I have obtained follow-up images of the comet on several occasions using LCO telescopes at both facilities, the more recent ones being based on a post-recovery orbit privately communicated by Syuichi Nakano that utilized my recovery positions
11 observations received at the 2008 return gave a light curve of m = 8.2 + 5 log d + 19.2 log r
It was reported to have brightened rapidly over the space of a few days in 2014 December, however the brightness after the "outburst" was roughly that given by the above light curve when corrected for aperture. A further increase in brightness to 7th magnitude was reported in mid January. Jonathan Shanklin observed it from Cambridge using 25x100B on January 18.75 and estimated it at 8.7, so the outburst appears to have been short-lived. Such short-lived events are perhaps part of the natural cascade of ejection of material from a comet and do not represent anything out of the ordinary.
These outbursts have been analysed in a publication to appear in ApJ see http://arxiv.org/abs/1510.06645. The authors suggest that the short-lived outbursts occurred over 2014 December 15.4 to 16.0 and 2015 January 15.5 to 16.0. The estimated mass involved, up to 500 tonnes, could be fitted into a large room giving an idea of the small scale of the event. They suggest that some radio meteor activity from the outbursts might take place on 2021 October 6/7.
Debris from the comet emitted at the 1995 perihelion passage was detected by southern hemisphere meteor camera and radar systems on 2021 September 28/29 and continuing. Further peaks are expected on October 7, associated with the 2008 and 2014 perihelion passages. The meteor shower has been named as the Arids. [CBET 5046, 2021 October 1]. Further calculations suggest the possibility of significant activity taking place between October 6 22:00 and October 7 01:00 associated with the 2014 outbursts. The South Atlantic, eg South Georgia, would be a favourable location to observe them. CBET 5049, 2021 October 4]
It is possible that the comet has an asymmetric light curve. 20 observations received at the 2014 return gave a light curve of m = 6.4 + 5 log d + 0.0933 abs(t-T-16)
The comet was discovered by Edwin Holmes from London on 1892 November 6. He had been observing in poor conditions, and decided to have a look at the Andromeda galaxy with his 32cm reflector before stopping for the night. He found an unexpected object that wasn't M31. Other observers were initially skeptical, but the comet was soon confirmed. It remained bright for several weeks before slowly fading, and then underwent another outburst in mid January, which again brought it within naked eye range.
At its eight following returns the comet was a faint object. It was reported in outburst by Spanish amateurs on 2007 October 24, when near opposition, but well past perihelion. The brightest estimates so far suggest that it reached 2.5. It is fading very slowly, and by mid November was still 3rd magnitude, although it had expanded to 40' diameter.
Observations with the Super-WASP wide-field imaging system at La Palma captured the start of the comet's outburst, and show that it brightened from 9.7 to 8.6 over 2.6 hours at a rate consistent with the linear expansion of an optically thick coma. Extrapolating backwards in time suggests that the outburst commenced on October 23.8.
Richard Miles has produced an explanation for the outburst involving the catalytic decomposition of H2O2. Richard continues to follow the comet with the Faulkes Telescope and in 2012 May detected another outburst with the comet at 4.4 AU from the Sun on its way in to perihelion. He further notes:
Comet 17P/Holmes is a fascinating comet having drawn our attention bigtime when it underwent a superoutburst brightening ~14 magnitudes on 2007 October 24. Interestingly, although its activity subsided, it did exhibit a clear outburst on 2009 Jan 04. The exact date is known thanks to monitoring by Luca Buzzi at Schiaparelli Obs. and by Richard Miles and George Faillace using the 2.0-m Faulkes Telescope North. The photometry can be seen here: http://www.britastro.org/~rmiles/Images/17P_2008-9_photometry.png In 2010 October, the comet reached aphelion at r = 5.188 AU and since then it has been approaching the Sun at an ever-increasing rate. The latest news is that although the cometary nucleus is still about 4.4 AU from the Sun, it has just undergone another distinct outburst, brightening by some 1.3 magnitudes as observed using the 2.0-m Faulkes Telescope South. Here is the photometry as measured using an aperture radius of 2.4": Date R mag Apr 13 21.1 Apr 19 20.9 May 15 19.7 May 17 20.1 May 18 20.2 The outburst probably occurred on 2012 May 12+/-2 as deduced from images taken on each of the above 5 epochs. See: http://www.britastro.org/~rmiles/Images/17P_2012May_outburstA.png Comet Holmes has some unusual characteristics. It is likely to be a very slow rotator: one unofficial estimate is a rotation period of 44+/-2 days. Observers located in the southern hemisphere may find this object to be a rewarding target for study. Its current apparition comes to an end in about August but the next one (2013 March - 2013 September inclusive) will be favourable. Perihelion occurs near solar conjunction in 2014 March and it then moves northwards occupying a similar region of the sky to its famous 2007 apparition. Given that the 2007 superoutburst was much more energetic than its outburst on the occasion of its discovery in 1892, the physical integrity of the cometary nucleus may have been compromised in some way so we may have to expect the unexpected from this object during the next few years. Assistance from the Faulkes Telescope Project led by Dr Paul Roche is gratefully acknowledged (see for example: http://en.wikipedia.org/wiki/Faulkes_Telescope_Project ) and without which none of this work would have been possible.
On 2014 September 7 a detection of the dust trail was reported in CBET 3969:
E. Lyytinen, M. Nissinen, H. J. Lehto, and J. Suomela, Helsinki, Finland, report that the convergence of dust ejected by 17P/Holmes in 2007 is now detected at the position in the orbit where it was originally released. The dust trail was centered at R.A. = 4h57m28s, Decl. = +41°39'02" (equinox 2000.0) on August 27d11h00m UT and oriented toward position angle 90.73 deg. The detection was made with the Californian iTelescope T24, after subtracting stacked images taken on August 25 and 26 from those taken on August 27. The peak surface brightness is 5.8 mag per square arcsecond fainter than the sky background (assumed to be 21.0 mag per square arcsec). This convergence is expected to be visible during the coming year, even when the earth is not in the plane of the comet orbit. The surface brightness of the dust trail is expected to increase until about Septrmber 15.54, when the comet approaches the point of its orbit where maximum dust outflow happened in 2007, and will only gradually decrease in the months thereafter, with predicted coordinates for the position of the trail given by Lyytinen et al. (2013, JIMO 41, 77-83).On 2015 January 27 a major outburst took place, increasing the brightness of the comet by around 3 magnitudes. The outburst was detected by Richard Miles in images taken with the Faulkes Telescope North on January 28.25 which showed a dramatic change when compared to images taken on January 26.29.
A paper submitted to MNRAS discusses the evolution of the dust trail and predicts that it should be visible in 2022 February and March.
In 2001 the comet was picked up by Michael Mattiazzo, who estimated it at 13th mag in mid June. By July 22 it had brightened to 11.4, a bit fainter than expected. Observing on August 28.11 with my 0.20-m SCT x75 I made it 10.3, DC4, diameter 1.7'. It reached a peak of around 10th magnitude in September and then slowly faded. By late November it was around mag 11.5 and by early January around 12.5.
The spacecraft Deep Space 1 successfully imaged comet 19P/Borrelly on 2001 September 22.
D. Schleicher, Lowell Observatory, writes: ``I obtained narrowband photometry of comet 19P on Sept. 18 and 19 using the Hall 1.1-m telescope at Lowell Observatory, yielding the following averaged production-rate results: log Q(OH) = 28.34; equivalent log Q(water; vectorial) = 28.41; log Af(rho) = 2.50 (cf. IAUC 7342). The radial fall-off of the dust is significantly steeper than the canonical 1/(rho), with Af(rho) decreasing by 1.9 times between rho = 20 000 and 110 000 km." [IAUC 7722, 2001 September 21]
Visual m_1 estimates: Sept. 1.11 UT, 10.0 (R. J. Bouma, Groningen, The Netherlands, 0.25-m reflector); 28.14, 9.9 (W. Hasubick, Buchloe, Germany, 25x100 binoculars); Oct. 11.08, 10.1 (B. H. Granslo, Fjellhamar, Norway, 0.20-m reflector); 18.68, 10.3 (Y. Nagai, Yamanashi, Japan, 0.32-m reflector); 24.96, 10.7 (V. S. Nevski, Vitebsk, Belarus, 0.30-m reflector). [IAUC 7739, 2001 October 25]
In 2009 Bernhard Haeusler imaged the comet between March 20 and June 12, detecting a sunward pointing tail, with a condensation possibly coming from jets active on the opposite pole to those seen by DS1.
Gerald Rhemann reported imaging a dust trail from the comet from 2021 November 1, with his most recent image on November 22. The comet is moving north and has reached 9th magnitude, though has quite a diffuse coma and is still quite low, so a difficult visual target from the UK. By the end of January it will be over 30 degrees altitude in a dark sky and should be easier to spot.
Observations over all returns between 1981 and 2015 are fairly consistent and give a mean aperture corrected light curve of m = 7.1 + 5 log d + 11.7 log r
Comet 21P/Giacobini-Zinner is the parent comet of the October Draconid meteors. In 2011 we passed just inside the comet's orbit 132 days before the comet. Predictions were made using the dust trail model and activity was predicted for October 8 most likely between 18 and 21 UT. A meteor outburst was observed on October 8, between 20:05 and 20:15 UT.
The comet was first discovered by Michael Giacobini at Nice observatory in December 1900 and was thought to have a period of 6.8 years. The next two returns were expected to be difficult to observe, but in October 1913, Ernst Zinner, of Bamberg, Germany, discovered a comet whilst observing variable stars in Scutum. This turned out to be the same comet, but the period had been incorrectly determined. The comet was missed at three unfavourable returns, so the 1998 return was the thirteenth apparition of the comet.
Martin Mobberley imaged the comet on 1998 October 14 and October 25 .
The comet reaches perihelion in 2012 February, but the return is unfavourable. Never-the-less a few observations were made during November when the comet was reported at between 12th and 13th magnitude. By December 22 it had brightened to 9th magnitude.
In 1998 223 observations received gave an uncorrected preliminary
light curve of
8.9 + 5 log d + 13.6 log r
In 2005 22 observations give an uncorrected preliminary lightcurve of 8.5 + 5 log d + 19.9 log r
Observations in ICQ format , last observation 1999 April 29, updated 1999 July 7.
22P/Kopff was discovered photographically by A Kopff at Konigstuhl Observatory in 1906, when it was around 11m. The next return was unfavourable, but it has been seen at every return since then. Following an encounter with Jupiter in 1942/43 its period was reduced and the perihelion distance decreased to 1.5 AU. The following return was one of its best and it reached 8m. The next return was unusual, in that it was 3m fainter than predicted until perihelion, when it brightened by 2m. It suffered another encounter with Jupiter in 1954, but this made significant changes only to the angular elements. 1964 was another good return and the comet reached 9m.
The 2002 return was not favourable and only a few observations were received.
The comet was around 13th magnitude in May and June during the 2009 return. It had brightened to nearly 9th magnitude by October.
An analysis of the data from 1996
gave a light
curve of 7.5 + 5 log d + 10 log r, but this was very
indeterminate. The 2009 data (62 observations) suggest
8.3 + 5 log d + 8.9 log r whilst the 2015 data (102 observations) suggest 5.7 + 5 log d +
19.3 log r , though a linear curve peaking
45 days after perihelion fits the data better.
1996 Observations in ICQ format reported to 1997 October 30.
2002 Observations in ICQ format reported to 2002 November 6, last observation 2002 September 29.
Thomas Lehmann reported imaging a long, faint dust trail extending over two degrees in an image taken on 2022 August 21. This was also imaged by Gerald Rehmann in July.
Comet 24P/Schaumasse Alexandre Schaumasse discovered comet 24P/Schaumasse during a visual search with the 400mm coude equatorial at Nice, France in 1911 December as a 12m diffuse object and it reaches a similar magnitude at average returns. The 1952 return was very favourable and the comet reached 5m, though there may have been an outburst. The orbit is relatively stable.
Martin Mobberley imaged the comet on 2001 February 13 and estimates the CCD magnitude as around 15 - 16. I observed on 2001 February 14.8 with the Northumberland refractor and immediately saw a diffuse object in the expected position, which I estimated at 13.6. This is rather brighter than the CCD magnitude and will need further confirmation. A further observation on March 12.8 put the comet at 13.2. I was able to glimpse it in the Thorrowgood refractor on April 24, estimating it at around 11.9.
78 observations received give an preliminary light curve of 7.7 + 5 log d + 29.2 log r
Observations in ICQ format reported to 2002 June 26, last observation 2001 June 20.
At the 2017 return it reached 10th magnitude during 2017 November.
On 2008 June 12 NASA released a news bulletin announcing the
discovery of a new mineral
in dust particles captured in the Earth's atmosphere, which were possibly from 26P.
The comet has passed 0.51 au from Jupiter in 1999 September and will pass 0.28 au from Jupiter in 2047 March.
Comet 27P/Crommelin 27P/Crommelin had a poor return in 2011. Its maximum elongation whilst brighter than 14th magnitude was only 37°. The comet is named for the BAA Comet Section Director, A C Crommelin, who first computed a linked orbit for comets seen in 1818, 1873 and 1928. It was quite well observed in 1984 when it served as a test comet for the International Halley Watch.
A few observations were made in early July 2011 when the comet was around 10th magnitude.
This annual comet has frequent outbursts and currently seems to be more often active than not, though it rarely gets brighter than 12m. It is possible that its pattern of behaviour has changed since the 1980s. The randomly spaced outbursts may be due to a thermal heat wave propagating into the nucleus and triggering sublimation of CO inside the comet, however there is no good correlation between enhanced CO and dust activity. Richard Miles has developed an alternative theoretical model to explain and predict outbursts of the comet. The comet nucleus has a diameter of around 60 km and is possibly a slow rotator, with a rotation period of around 58 days, though there is a wide range of estimates for the rotation rate down to as little as 14 hours. The comet has been in a near circular orbit since a Jupiter encounter in 1974. In October 2037 the comet encounters Jupiter in an approach to 0.9 au, which will increase the eccentricity and perihelion distance of the orbit. These occasional encounters through a "gateway region" give it a 60% chance of becoming a Jupiter family comet within the next few hundred years. [Most Jupiter family comets go through this low eccentricity gateway region just exterior to Jupiter, with about 75% of such comets either entering or leaving the family through the gateway. 2019 LD2 (P/ATLAS) is another comet that might undergo such a transition. It approaches to 0.1 au from Jupiter in 2028 May, though this encounter will increase the perihelion distance. It may subsequently become a JFC in 2063.] 29P is an ideal target for those making electronic observations and it should be observed at every opportunity.
1996 Early in the year it was in outburst for several months.
1997 In February and early March 1997 the comet was in outburst, peaking at around 12th mag. It was not seen in April, but returned to visibility in early May, rising to 12th mag late in the month. I observed it at 13.7: on May 12.95 with the Northumberland 0.30-m refractor. On May 29.97 it was 12.0: in my 0.20-m T x 75, dia 1.8', DC3. Andrew Pearce reports glimpsing it at around 14th mag in his 0.41-m reflector at the end of December 1997.
1998 Further reports suggest that the comet brightened to around 12th mag visually and then faded to 14th mag. Another outburst commenced in mid March 1998 according to IAUC 6844 and the comet is now around 13th mag, though I was unable to see it on April 28.9, when it was fainter than 13.2. It may be undergoing another outburst at around 13th mag (May 30).1999 Andrew Pearce discovered it in outburst on 1999 March 31. It was well condensed and so relatively easy to see, but faded below 14th mag. Reports suggest another outburst to around 13th magnitude in early June. Jose Aguiar reported it in outburst once again at the beginning of July.
2000 Jose Aguiar reported as possibly being in outburst on July 1
2001 The comet is undergoing another outburst, as shown by the following total magnitudes (CCD unless otherwise indicated): Apr. 22.80 UT, 15.5 (A. Nakamura, Kuma, Ehime, Japan, 0.60-m reflector); 28.44, 15.7 (A. Hale, Cloudcroft, NM, 0.2-m reflector); May 17.69, 13.2 (K. Kadota, Ageo, Saitama, Japan, 0.18-m reflector); 18.71, 13.4 (Kadota); 19.73, 12.0 (K. Yoshimoto, Hirao, Yamaguchi, Japan, 0.25-m reflector; visual); 27.77, 13.5 (Nakamura). [IAUC 7640, 2001 June 1] Further outbursts have taken place and the comet remains at around 12th magnitude into August.
2002 This comet appears again to be in outburst, as indicated by the following total-magnitude estimates (visual unless otherwise noted): Mar. 20.83 UT, [16: (T. Kojima, Chiyoda, Japan, 0.25-m reflector + CCD); 27.80, 14.4 (Kojima); May 8.46, 13.5 (A. Hale, Cloudcroft, NM, 0.41-m reflector); 9.46, 13.3 (Hale); 21.45, 13.3 (Hale); June 8.39, 12.3 (Hale; near-stellar appearance); 9.75, 12.0 (A. Nakamura, Kuma, Ehime, Japan, 0.60-m reflector + CCD; strong condensation). [IAUC 7918, 2002 June 13]
Carlos Labordena (Spain) reported the comet in outburst on November 1, at 12th magnitude with a well condensed coma. Michael Mattiazzo (Australia) also reported the comet bright, with the comet at around 14th magnitude through most of October, brightening at the end of the month. The degree of condensation was quite variable suggesting a series of outbursts, with perhaps one around October 27 and another around November 4.
2003 Salvador Sanchez, Jaime Nomen and Reiner Stoss observed the comet on the morning of May 22 with the remotely controlled 30-cm telescope of the Observatorio Astronomico de Mallorca. The comet looked to be in outburst. The measured magnitude was 13.5 N on 80s CCD frames at an SNR of 30. Juan Jose Gonzalez reported the comet at 13.1 on July 23.02. A further outburst was reported at the end of September.
Seichi Yoshida notes the following pattern of activity:
The high level activities in 2002 and 2004, and the low level activity in 2000 are remarkable.
1997 Two outbursts occured, but faint in general. 1998 After outburst in late January, it kept bright for a while though diffused. Only one outburst. Not visible visually in the latter half. 1999 Not visible visually in the former half. After outburst in late March, it kept bright for a while though diffused. Only one outburst. 2000 No outburst. Not visible visually almost at all. 2001 Major outburst occured in August. Some other small outbursts occured, too. Every outburst was short, and it became invisible soon. 2002 Outbursts often occured. It was brighter than 13 mag in many times. It became so faint temporarily in July. 2003 Outbursts often occured, but small, and only 13 mag at best. 2004 Outbursts frequently occured. It kept bright around 12 mag all through the year.
2005 The comet was reported in outburst in July. A second outburst was reported in mid August. Another outburst began in mid September and I estimated it at 12.1 and DC6 in the N'land refractor x185 on September 18.96 There was another outburst in mid December and it was an easy object in the N'land refractor on December 17.9
2006 The comet was reported in outburst at around 13th magnitude in mid July 2006. An image taken by Martin Mobberley on December 16.8 showed the comet at around 12th magnitude.
2007 It spent the first quarter of the year in Taurus before sinking into solar conjunction. It emerged into the morning sky of Auriga in August, reaching opposition there at the end of the year. Generally outbursts seem not to have been so frequent in 2007, however it was reported in outburst at 13th magnitude in late December.
2008 It spent the first third of the year in Auriga before sinking into solar conjunction. It emerged into the morning sky of Gemini in August, and spent the last third of the year in Cancer. Unusually there was no opposition in 2008. A major outburst occurred in January and it reached 11th magnitude mid-month. A further outburst occurred in mid September, when it again reached 11th magnitude. It seems to have spent most of this year within visual range. Another outburst commenced around December 18.
2009 The comet begins the year retrograding in Cancer and passes into Gemini around the time of opposition on January 17. It resumes direct motion around the time of the northern spring equinox and will be lost to UK observers in early May. It is in solar conjunction on August 1. For UK observers it will become observable in the morning sky in October, by which time it is in Leo.
Richard Miles notes that it was at opposition on January 17, when it had a phase angle of only 0.5 degrees and this may have lead to an opposition effect brightening. Some jet structure was observed in the coma around this time, and he further notes that it will be important to follow their evolution as the comet is reported to be a slow rotator (about 60 days).
2010 The comet underwent a major outburst in February, reaching 10th magnitude. This was around the time of opposition, when the phase angle was 0.3 degrees.
2011 29P/Schwassmann-Wachmann underwent a minor outburst at the end of February reaching 12th magnitude. Another outburst took place in late March, with the comet again reaching 12th magnitude.
Richard Miles is developing a theoretical model to explain and predict outbursts of the comet.
He successfully predicted an outburst in early March, and predicts another around April 28 with
a 50% probability of occurrence.
Richard Miles reported that the comet was in outburst on 2015 February 3.76, having brightened to around 14th magnitude.
He reported that a second outburst occurred on February 26.15.
2016 A major outburst occurred in July.
2021 A complex major outburst occurred in September. Richard Miles suggested that major activity could continue into 2024.
2022. A massive outburst commenced on November 21.83, with a smaller outburst following on December 26.61, according to Richard Miles.
2023. Richard Miles reported a further outburst commencing on March 21.1.
At the 2004 return the comet was reported at 13th magnitude in mid November. It reached 11th magnitude at the end of the year. Observations in ICQ format, last observation 2005 May 4, updated 2005 May 11.
36 observations received in 2004 give a preliminary light curve of 6.9 + 5 log d + 16.7 log r
Electronic images in 2014 November showed a distinct tail.
16 observations received in 2014/15 give a preliminary light curve of 7.0 + 5 log d + 17.2 log r
49 observations received in 1999 give an uncorrected preliminary light curve of 10.6 + 5 log d + 11.8 log r
Observations in ICQ format , last observation 1999 October 10, updated 1999 October 31.
Studies with the JWST in 2022 suggest a nucleus diameter of around 2.3 km and outgassing of CO2.
At the 1973 return, which was similar to the 1907 return, it underwent a major outburst and reached 4m, before fading and then undergoing a second outburst. Alternate returns are unfavourable but the comet has been observed at a few of them.
The comet appears to be in outburst, as indicated by the following visual m_1 estimates: 2000 Nov. 27.53 UT, 10.2: (A. Hale, Cloudcroft, NM, 0.41-m reflector); 28.83, 10.5 (Y. Nagai, Yamanashi, Japan, 0.32-m reflector); Dec. 1.82, 10.4 (M. Tsumura, Wakayama, Japan, 0.32-m reflector). [IAUC 7536, 2000 December 5]
The comet appears to be continuing its rapid brightening (cf. IAUC 7536), as indicated by the following m_1 estimates: Dec. 5.82 UT, 11.1 (S. Yoshida, Ibaraki, Japan, 0.25-m reflector; visual); 6.52, 11.4 (A. Hale, Cloudcroft, New Mexico, 0.41-m reflector; visual); 15.83, 8.7 (K. Kadota, Ageo, Saitama, Japan, 0.18-m reflector + CCD; 3' coma and 16' tail). [IAUC 7543, 2000 December 15]
28 observations received give a preliminary light curve for the outburst of 6.1 + 5 log d + 0.117 * abs(t - T - 18.5)
Observations in ICQ format , last observation 2001 January 18, updated 2001 June 23.
David Jewitt notes that the nucleus has a diameter of around 700m and shows a rapid change in rotation period.
Comet 43P/Wolf-Harrington is at its brightest (12th mag) at the beginning of the year, and slowly fades as its elongation in the evening sky decreases. It is favourably placed and CCD observers should certainly have a go at following the comet. This will be the tenth observed return of the comet, which was discovered in 1924, then lost until 1951. The comet is in a chaotic orbit, and made a close approach to Jupiter in 1936 which reduced its perihelion distance from 2.4 to 1.6 AU. It made an exceptionally close (0.003 AU) approach to Jupiter in 1841, which switched its previous perihelion distance into the new aphelion distance.
I observed it on 1997 September 9.14 in my 0.20-m SC, making it 13.4:, dia 0.9' and DC2. On October 10.17 it was a weakly condensed diffuse glow in the 0.30-m refractor x170, DC2, diameter 1.0'. On November 4.2 it was 12.6 in the 0.30-m refractor.
Observations in 1997 gave an uncorrected
preliminary light curve of
9.3 + 5 log d + 12.9 log r
Observations in ICQ format, last observation 1998 January 31, updated 1998 February 4 .
Observations in ICQ format, last observation 2003 December 20, updated 2003 December 29.
Observations in ICQ format, last observation 2002 February 24, updated 2002 April 2 .
2001makes its 10th observed return since discovery in 1948 (it was missed in 1959). It has had several close encounters with Jupiter, the most recent in 1983 which made dramatic changes to w and W . The perihelion distance has steadily decreased and is now the smallest it has been for the last 200 years. It can approach quite closely to the Earth and will do so in 2011 (0.06 AU) and 2017 (0.08 AU). At present the MPC only lists eight approaches closer than 0.06 AU, and five of these are by periodic comets. It was well observed at its return in 1995/96. The comet was in the field of the SOHO LASCO coronagraphs in March.
On 2001 Apr. 4.42 UT, K. Kadota, Ageo, Saitama, Japan, reported m_1 = 10.5 and coma diameter 0'.8 (0.18-m reflector + CCD).
Gabriel Oksa reported a visual observation on 2001 April 17.8, when he estimated the comet at 9.3 in a 0.15m R x60, coma 2.5' diameter, DC4.
22 observations received give a
preliminary light curve of
11.0 + 5 log d + 11.1 log r
Observations in ICQ format, last observation 2001 May 19, updated 2001 June 25 .
2011This year there was an excellent return of 45P/Honda-Mrkos-Pajdusakova. Southern Hemisphere observers are likely to pick it up near opposition in July, when it is a 12th magnitude object in Pisces Austrinus. It heads even further south, brightening rapidly as it passes only 0.06 au from the Earth on August 16, when it was seen with the naked eye. It passes through conjunction at the end of the month and fades a little, but brightens again as it approaches perihelion at the end of September. UK observers had a chance to see it between mid September and mid October, although it was quite low in the morning sky.
32 observations received give a
preliminary light curve of
13.2 + 5 log d + 21.1 log r
The comet was picked up at 11th magnitude in early December. It made a close pass to the Earth in 2017 February.
The comet was visible in SOHO C3 images from April 21 to 28, appearing a little brighter than expected, and possibly over a degree off track when compared to some ephemerides. Ground based imagers were able to capture it in May, providing astrometry to correct the orbit. The Earth encountered dust from the comet on 2022 August 16/17, when our planet passed 0.0038 au from the dust trail centre. Meteors from the newly designated August delta Capricornids were detected by the CAMS network.
Looking to the future it passes 0.2 au from Jupiter in 2030. There are some very close passes by Venus, but only moderately close passes by the Earth.
Carl A Wirtanen discovered 46P/Wirtanen at Lick in 1948. It is in a chaotic orbit, and its perihelion distance was much reduced due to approaches to Jupiter in 1972 and 84. It has been reported to outburst, but BAA data suggests that it has just been rejuvenated after the perihelion distance was reduced. A December perihelion would give a close approach to the Earth, and as the present period is now less than 5.5 years this will be achieved in 2018, when the comet could reach 3rd magnitude.
There is to be a Pro-am observing campaign on the comet in 2018. There is a brief observing window for UK observers in September which will be useful for determing the magnitude parameters at this return, but it is best seen from the southern hemisphere during this period. It quickly moves into the evening sky in mid November, and could be a naked eye object in December. It makes a close approach to Earth on 2018 December 16, passing 0.078 au from us. It could remain within visual range until March.
Observations at the 2018 return detected spiral structures in the coma which were interpreted as indicated a rotation period of 8.91 hours with the nucleus in a simple state of rotation. [CBET 4571, 2018 November 10]
It peaked at around 10th mag in 1997 March.
Observations in ICQ format, last observation 1997 May 31, updated 1997 July 28
The comet was a morning object in 2002. The first visual observation was reported in early August when the comet was around mag 11.5. Observations suggest that the comet peaked at around 9th magnitude in late September. I observed it on October 19.18, estimating it at 10.4 in my 20cm LX200 x75. The observations are currently best fitted by a linear type light curve, with the comet brightest about a month after perihelion.
Observations received (26) give a preliminary light curve of 7.7 + 5 log d + 0.0427*(t-T+30.4)Observations in ICQ format, last observation 2002 November 17, updated 2003 January 2
2007/8 This was a relatively good return with the comet reaching 9th magnitude in the evening sky around the time of its February perihelion. The comet traveled eastwards, not that far from the ecliptic, crossing to northern declinations in late January and crossing north of the ecliptic in early February.
67 observations received give an uncorrected preliminary light curve of m = 8.5 + 5 log d + 20.5 log r.
David Jewitt notes that the nucleus has a diameter of around 600m and shows a rapid change in rotation period. They also note that another paper reported changes in the period before and after perihelion which largely cancelled out.
Michael Mattiazzo recovered the comet at 14.0 on 2000 July 4.
7 observations received give an uncorrected preliminary light curve of m = 2.1 + 5 log d + 25.9 log r.
Observations in ICQ format , last observation 2000 August 28, updated 2000 August 30.
CCD observations in 2005 suggested a likely 14th magnitude.
Visual observations in 2011 ranged between 10th and 14th magnitude between September and December, but did not fit any clear pattern.
Observations in ICQ format, last observation 1999 November 30, updated 2000 February 25.
Comet 51P/Harrington was P. Manteca, Observatorio de Begues (near Barcelona), reports that his observations on Dec. 6.1 UT (0.31-m f/6.3 Schmidt- Cassegrain reflector + CCD) showed this comet to have split, the two components being separated by some 10" on an east-west line. Each around mag 17.0-17.4, the western component was perhaps up to 0.4 mag brighter than the eastern, which is evidently the one that was under observation during July-November. On Dec. 7.0 and 7.9 Manteca gave m_1 = 16.4 for the eastern component and m_1 = 16.6 for the western. The eastern component is also clearly the object defined as component A at the comet's 1994 apparition, when two much fainter components, B and C, were also recorded with an effective perihelion time almost 0.3 day later (cf. IAUC 6089). The current western component is therefore to be denoted as component D, and its effective perhelion time on 2001 June 5 is only about 0.006 day later than that of component A. The splitting was confirmed by R. Naves and M. Campas (Observatorio Montcabre, also near Barcelona; 0.25-m f/3.3 Schmidt-Cassegrain reflector + CCD), who gave m_1 as 16.9 for component A and 16.7 for component D on Dec. 6.9 and 16.2 for component A and 16.3 for component D on Dec. 7.9. R. Ferrando (Observatorio Pla D'Arguines, near Valencia; 0.30-m Schmidt-Cassegrain reflector + CCD) gave m_1 as 16.5 for component A and 16.7 for component D on Dec. 7.9. The comet is noticeably brighter than the predicted magnitude given in the ephemeris on MPC 43692. [IAUC 7769, 2001 December 8]
Z. Sekanina, Jet Propulsion Laboratory, writes: "Preliminary analysis of the reported astrometric data for the two nuclei (IAUC 7769, MPEC 2001-X45) indicates that companion D separated from primary A on Sept. 5.6 +/- 3.6 TT, or 3 months after perihelion, with a relative deceleration of 59 +/- 8 units of 10**-5 the solar attraction. The two separation parameters are, however, highly correlated and probably more uncertain than their formal errors suggest. Unless too faint, the companion should have shown up in high-resolution images taken since mid-October, when it was about 4" to the west of the primary. Predicted separation distances and position angles (0h TT): 2001 Dec. 17, 12", 268 deg; 2002 Jan. 6, 10", 263 deg; Jan. 26, 9", 255 deg; Feb. 15, 9", 249 deg; Mar. 7, 11", 248 deg; Mar. 27, 15", 251 deg; Apr. 16, 19", 255 deg; May 6, 24", 259 deg." K. Kadota, Ageo, Saitama, Japan, reported CCD observations that indicated an intrinsic brightening of more than two magnitudes between Aug. 22 and Sept. 23 (an outburst confirmed by other observers). [IAUC 7773, 2001 December 13]
The comet was recovered on 2008 July 28.43 by the Catalina Sky Survey, with delta T of 0.98d. Further observations were made in October 2008, when the comet was around 17th magnitude. The comet was recovered at its 2015 return at the CAO, San Pedro de Atacama in 2015 May, when it was 18th magnitude.
Observations in ICQ format, last observation 2001 December 12, updated 2001 December 19.
Comet 52P/Harrington-Abel was found in outburst at 12th mag by Alain Maury, Observatoire de la Cote d'Azur, on CCD images taken on July 21.1 UT when its predicted magnitude was about 21. [IAUC 6975, 1998 July 25]. A second outburst may have occured some 80 days before perihelion.
The comet reached perihelion and opposition in late January 1999. This is the seventh observed return of the comet since its discovery in 1954 and it has never became brighter than 17th magnitude at previous returns. Normally it would not be expected to get brighter than 15th magnitude at this return, however it was found in outburst at 12th magnitude in July 1998 and was 7 magnitudes brighter than expected. I glimpsed it a few times in mid March with the Northumberland, making it around 13th mag. Observing on April 9/10 with the Northumberland I could not see the comet, estimating it fainter than 13.8. NGC 2455 which lay nearby was clearly visible and estimated at 13.1 compared with the catalogued magnitude of 13.2.
Observations received so far (34) give an uncorrected preliminary light curve following the second outburst of m = 10.2 + 5 log d + 0.0416abs(t-T+23.1).
Observations in ICQ format, last observation 1999 April 29, updated 1999 August 12.
Comet 53P/van Biesbroeck 53P/van Biesbroeck is an interesting object. George van Biesbroeck discovered it at Yerkes observatory in September 1954. Stan Milbourn and George Lea calculated the best recovery orbit and the comet was duly recovered in May 1965. Back calculating the orbit shows that it made a moderately close approach to Jupiter in 1850, which reduced q from 2.7 to 2.4 au and reversed the nodes. The pre 1850 orbit is very similar to that of 42P/Neujmin 3 and it is likely that they are fragments of the same parent.
The comet reached 13th magnitude at its 2016 return.
Observations in ICQ format, last observation 2003 July 26, updated 2003 December 9.
Comet 54P/de Vico-Swift-NEAT K. Lawrence, S. Pravdo, and E. Helin, Jet Propulsion Laboratory, report the discovery on Oct. 11.22 UT of a 19.3 mag comet (with a nuclear condensation of diameter about 4" and a tail about 20" long toward the south-southwest) on NEAT images taken at Palomar. M. Hicks reports that images taken by J. Young at Table Mountain on Oct. 12.3 (through cirrus clouds) show a diffuse coma and a faint 5" tail to the southwest. D. Balam, University of Victoria, reports that images taken by J. Clem with the 1.82-m Plaskett telescope (also on Oct. 12.3) also show the object to be cometary in appearance (3 pixels, or 3".3, larger than nearby stars). [IAUC 7991, 2002 October 12]
The comet was named 2002 T4 (P/NEAT), but it was quickly realised that this was not a new comet:
A. Nakamura, Kuma, Ehime, Japan, reports that K. Muraoka (Kochi, Japan) has identified comet P/2002 T4 (cf. IAUC 7991) with 54P, last seen in 1965. The indicated correction to the prediction on MPC 34423 (ephemeris on MPC 46016) is Delta(T) = -7.5 days. Calculations by B. G. Marsden, Smithsonian Astrophysical Observatory, indicate that the comet passed 0.16 AU from Jupiter on 1968 Oct. 18.[IAUC 7992, 2002 October 13]
At its 2009 return it was recovered by David Herald at Kambah, and by C. Rinner and Francois Kugel at Observatoire Chante-Perdrix, Dauban. in mid August at around 19th magnitude. This is the first time the comet has been observed at successive apparitions (previous returns were 1844, 1894, 1965 and 2002).
Observations in ICQ format, last observation 2004 October 12, updated 2004 October 19.
Comet 57P/du Toit-Neujmin-Delporte is too faint for observation.It was observed in outburst at the 1996 return and in July 2002 NEAT discovered a secondary component. A further 18 components were discovered by Fernandez et al at the University of Hawaii.
A faint object reported as a possible NEO candidate on 2002 July 12.21 by S. Pravdo, Jet Propulsion Laboratory, on behalf of NEAT and described as appearing cometary was recognized at the Minor Planet Center as being on the line of variation and to have the motion of comet 57P, but to be displaced from that brighter comet (which was not included in the dataset) by more than 0.2 deg on the 1.2-m Palomar Schmidt frames. NEAT had reported the brighter comet on July 1 (see MPEC 2002-N14), but a check with Pravdo yesterday did not reveal anything obvious at the July 1 expected position of the new object. Following a request by the Minor Planet Center, M. Tichy and J. Ticha (Klet, KLENOT 1.06-m reflector) located the new object last night, describing it as diffuse and having a coma of diameter 8"-10"; as did G. Masi and F. Mallia (Campo Catino, 0.8-m f/8 reflector), whose coaddition of five images (for a total integration of 20 min) showed a well-defined 12" coma and a delicate northeast-southwest elongation. The object was again included in today's NEAT NEO-candidate report but with no remark about its appearance.
The positions are fully consistent with the orbital elements for comet 57P on MPC 45964 (ephemeris on MPC 44939) with T for this "component B" delayed by 0.19 day (i.e., to 2002 July 31.37 TT). It should be noted that comet 57P was anomalously bright at its unfavorable 1996 return (T = 1996 Mar. 5.7; m1 = 13.3 at the first postperihelic observation on July 24.8--see MPC 27482--some 5 mag brighter than expected). [IAUC 7934, 2002 July 13]
Y. R. Fernandez, D. C. Jewitt, and S. S. Sheppard, University of Hawaii, report the detection of an additional 18 components (C-T) of comet 57P (cf. IAUC 7934) in observations taken on July 17.5 and 18.4 UT with the University of Hawaii 2.2-m reflector. R-band magnitudes range from 20.0 to 23.5. The components range from well condensed to diffuse with little central condensation and have comae of diameter 1"-5". Components I, K, L, N, P, and T show a lack of central condensation. The components are delayed with respect to T = 2002 July 31.181 TT for component A by the following times (in days): C, +0.012; D, +0.037; E, +0.053; F, +0.078; G, +0.156; H, +0.164; I, +0.170; J, +0.180; (B, +0.188); K, +0.194; L, +0.194; M, +0.224; N, +0.226; O, +0.240; P, +0.271; Q, +0.309; R, +0.311; S, +0.313; and T, +0.354. [IAUC 7935, 2002 July 20]
Total magnitude estimates for the primary component (visual unless otherwise noted): June 5.71 UT, 15.6: (A. Nakamura, Kuma, Ehime, Japan, 0.60-m reflector + CCD); 9.68, 15.4 (Nakamura); 18.70, 15.7 (K. Kadota, Ageo, Saitama, Japan, 0.18-m reflector + CCD); July 5.27, 13.4 (A. Hale, Cloudcroft, NM, 0.41-m reflector); 10.24, 13.3 (Hale); 10.95, 14.1 (K. Sarneczky, Agasvar, Hungary, 0.38-m reflector); 11.59, 14.5 (Y. Ezaki , Toyonaka, Osaka, Japan, 0.30-m reflector + CCD). [IAUC 7937, 2002 July 24]
Z. Sekanina, Jet Propulsion Laboratory, writes: "Very preliminary analysis of the relative astrometry of the two brightest nuclei (cf. MPEC 2002-O10) has been completed, employing a new computer code recently developed by P. W. Chodas and myself. The parameters of the standard model for split comets are now determined with full account of the planetary perturbations and the nongravitational effects on the principal nucleus. The results suggest that nucleus B could have broken off from primary A near perihelion in 1996. If the event had occurred exactly at perihelion, plausible values for the nongravitational deceleration (4-8x10^-5 solar attraction, as B is obviously a persistent companion; cf. Sekanina 1982, Comets, ed. L. L. Wilkening, pp. 251-287) require that B separated from A with a reasonably low velocity, whose transverse component ranged from 0.5 to 1 m/s in the direction opposite the orbital motion and whose normal component was some 0.4-0.5 m/s toward the north orbital pole. These solutions are independent of the radial component of the separation velocity. Similar solutions are also found for separation times 100 days before and after perihelion, except that the deceleration then correlates with both the transverse and radial components. Because of the comet's extremely low orbital inclination, it is doubtful that the separation parameters can ever be determined with high accuracy. All examined solutions yield essentially the same ephemeris, which shows that the projected separation of B from A will diminish in the coming weeks. The offsets and position angles are as follows (0h UT): 2002 Aug. 4, 853", 259.1 deg; 14, 814", 259.1; 24, 758", 259.0; Sept. 3, 694", 258.7; 13, 631", 258.3; 23, 571", 257.7; Oct. 3, 516", 257.0. It is unlikely that companions C-T (cf. IAUC 7935) are all products of the same event. In particular, C-F were probably released from A more recently than B was. Some of nuclei M-T may be fragments of B, but a more complex fragmentation hierarchy is also possible. Accurate astrometry on existing images and additional observations may allow one to make more, but not very, definite statements in the future.'' [IAUC 7946, 2002 August 3]
Further to his report on IAUC 7946, Z. Sekanina writes: "Using the code developed by P. W. Chodas and myself, I was able to link the observations of the Aug. 7 secondary nucleus (MPEC 2002-P75) with those of companion F on July 17 (MPEC 2002-P30). An excellent fit (mean residual 0".26) suggests that F separated from nucleus A most probably in the second half of May 2001, a little more than 400 days before perihelion at a heliocentric distance of about 3.6 AU. By contrast, all attempts to fit the offsets on the assumption of a separation near the 1996 perihelion have failed, leaving systematic residuals of a few arcsec. The 2001 solution is rather insensitive to the adopted nongravitational deceleration, if it is on the order of several units of 10**-4 solar attraction. The derived separation velocity is then about 5 m/s, mostly in the orbital plane. The predicted separation distances and position angles (0h TT): 2002 Aug. 14, 401", 259.0 deg; 24, 398", 259.0 deg; Sept. 3, 393", 259.0 deg; 13, 387", 258.8 deg; 23, 383", 258.4 deg; Oct. 3, 381", 257.8 deg. Confirmation observations are needed to understand the fragmentation sequence, because major deviations from this ephemeris would indicate a different splitting scenario."
Total visual magnitude estimates: July 28.87 UT, 12.9 (M. Reszelski, Szamotuly, Poland, 0.41-m reflector); Aug. 8.88, 13.9 (W. Hasubick, Buchloe, Germany, 0.44-m reflector); 12.94, 13.3 (R. J. Bouma, Groningen, The Netherlands, 0.31-m reflector). [IAUC 7957, 2002 August 19]
It was again reported in outburst in 2021, with Francois Kugel finding it at 12th magnitude on October 17, some five magnitudes brighter than the MPC elements would predict.
Observations in ICQ format reported to 1996 September 15 (last observation)
Observations in ICQ format, last observation 2002 August 8, updated 2002 November 6
In 2020 April it was spotted in SWAN images by Hua Su at an estimated 10th magnitude and was posted on the PCCP as SWAN20A. Confirmation came from ground based observers including Michael Mattiazzo and it was clear that the non-gravitational forces acting on the nucleus had delayed the return to perihelion. Hirohisa Sato (and others) computed new orbits with new non-gravitational parameters that link the 1995 and 2020 observations, giving perihelion on May 27.4. The comet is some 6 magnitudes brighter than might be expected from the linear light curve, suggesting that it is in outburst. Following posting here, CBET 4747 and MPEC 2020-G76 were issued on 2020 April 8, each with differing accounts of the recovery and with the MPEC close to the account given here.
Observations in ICQ format, last observation 2000 February 5, updated 2000 August 16.
Observations in ICQ format, last observation 1999 March 22, updated 1999 May 24.
Comet 62P/Tsuchinshan was discovered at Purple Mountain Observatory, Nanking, China in 1965, following a close approach to Jupiter in 1960, which reduced the perihelion distance from 2 to 1.5 au. The inclination is decreasing, combined with a rapid regression of the node and rotation of the orbital plane. Unusually, the comet's name derives from that of the observatory rather than those of the discoverers. At a good apparition such as in 1985 it can reach 11m and as the perihelion distance will continue to decrease future returns may be even better. At the 1998 return the comet was recorded at around 13th magnitude. At the 2004 return it was picked up as a 13th magnitude object in the October morning sky, by Michael Jager. I was barely able to see it with the N'land refactor x230 on 2005 January 21.2, although nearby galaxies of 12th magnitude were easy. The comet brightens quite quickly and at the 2017 return slightly caught observers by surprise as it brightened to 11th magnitude. It has again brightened rapidly at the 2023 return and could reach 8th magnitude.
Observations received in 1998 give an uncorrected
preliminary light curve of
7.2 + 5 log d +  log r
The 19 Observations received in 2004 do not give a well defined light curve,
8.8 + 5 log d + 19.1 log r
Nakano reported observations made by T. Kojima, Chiyoda, on 1999 October 24.83 of this 13-year-period comet, missed at its 1986 return. These observations confirm a single-night detection at mag 22.4 by Hergenrother (1.5-m Catalina reflector) on 1999 February 14. The prediction on MPC 27082 requires correction by Delta T = -0.35 day. Further details were given on MPEC 1999-V18. Kojima (0.25-m f/6.3 reflector) reported the comet at m1 = 16.5 and as diffuse without a tail on Oct. 24, at m1 = 15.9 and diffuse with condensation and a coma diameter of 30" on Nov. 4. [IAUC 7302, 1999 November 6].
was a difficult object of around 14th magnitude in the Northumberland refractor
on 2000 January 5 and reached its brightest at around 13th magnitude towards
the end of the month.
26 observations reported to the BAA and ICQ give a final light curve of 8.9 + 5 log d +  log r. The log r range was too small to determine the magnitude parameter independently.
Observations in ICQ format, last observation 2000 March 5, updated 2000 August 16.
Juan Jose Gonzalez observed it at 11th magnitude in his 20cm Schmidt-Cassegrain at his Spanish mountain location on 2013 March 1.8
11 observations reported to the BAA give a preliminary light curve of 8.1 + 5 log d +  log r. The log r range is too small for a reliable determination of the parameter.
Comet 64P/Swift-Gehrels The comet was discovered in 1889 and then lost until it was recovered by chance by Tom Gehrels in 1973. There was a favourable apparition in 1981 when it reached 11th magnitude. The 2018 return should be similar. I was able to observe the comet with the Northumberland refractor on 2018 December 9, making it 10.1.
The comet was discovered in 1970 after a perturbation by Jupiter in 1965 had reduced the perihelion distance from 3.39 to 2.44 AU. In 1980 two prediscovery images were found on Palomar plates taken in 1954. The comet can be followed all round the orbit as it has a relatively low eccentricity of 0.32.
1997 I observed it with a 0.20-m SC on 1997 September 6.09 and made it 13.5:, dia 0.8', DC3.
Observations in ICQ format, last observation 1997 December 21, updated 1998 February 4 .
2002/03 It will be at moderate southern declination throughout the apparition and is essentially unobservable from the UK.
The visual and CCD observations received so far (20) give an uncorrected
preliminary light curve for the 2002 apparition of
8.6 + 5 log d + 6.8 log r
Observations in ICQ format, last observation 2003 October 13, updated 2003 December 9.
The visual and CCD observations received so far (25) give an uncorrected
preliminary light curve for the 2010 apparition of
7.9 + 5 log d + 6.6 log r
Observations in ICQ format, last observation 2010 October 26, updated 2010 November 3.
Comet 66P/du Toit 66P/du Toit is usually only observed at alternate returns - its return in 1988 was about the worst possible. It was discovered by Daniel du Toit at the Boyden Observatory in South Africa on 1944 May 16. The discovery return was a good one, with the comet approaching to within 0.5 au of the Earth, and the comet reached 10th magnitude. It was not found at the 1959 return, nor was it initially found in 1974, however in January 1975 a further inspection of search plates taken ten months previously revealed a diffuse image of the comet. The 2018 return is moderately favourable, and the comet could reach 13th magnitude, however, as at the discovery return, it will essentially be a Southern Hemisphere object.
J. V. Scotti recovered the comet with the 1.8-m Spacewatch II telescope at mag 20.3-20.7 on 2003 Mar. 10 and 11. The astrometry, revised orbital elements, and an ephemeris appear on MPEC 2003-E57. The indicated correction to the prediction on MPC 40670 is Delta(T) = -0.25 day. [IAUC 8093, 2003 March 14] The comet was previously seen in 1944 and 1974.
Observations in ICQ format, last observation 2003 September 21, updated 2003 December 9.
Comet 67P/Churyumov-Gerasimenko was discovered in 1969 September, by Klim Churyumov and Svetlana Gerasimenko on a plate taken for 32P/Comas Sola at Alma Ata observatory. It reached its present orbit after a very close encounter (0.05 au) with Jupiter in 1959, which reduced the perihelion distance from 2.74 to 1.28 au. At a good apparition, such as in 1982, when it approached the Earth to 0.4 au and was well observed by the comet section, it can reach 9m.
Observations in ICQ format, last observation 2002 December 11, updated 2003 January 6.
The 2008 return was not a particularly good apparition, as the comet remained at a relatively small elongation from the sun. It was recovered by Gustavo Mueller at Observatorio Nazaret with a 0.30m Schmidt-Cassegrain on 2008 June 1.12, when it was 19th magnitude.
The 2015 return was important as the Rosetta spacecraft orbited the comet, however it was not a particularly good one as the comet was an early morning object. As at previous apparitions it was brightest some 40 days after perihelion, when it reached 11th magnitude. The comet was observed by Juan Jose Gonzalez on August 19 from a high mountain site, when he estimated it at 12.2 in his 20cm Schmidt-Cassegrain. This was fainter than expected, which may have implications for the in situ science.
The visual and electronic observations received so far (68) give an uncorrected
preliminary light curve for the 2015 apparition of
10.0 + 5 log d + 7.7 log r, though a linear curve peaking 40 days after perihelion fits the data better.
It is showing similar behaviour during the 2021 apparition, which is more favourable and the comet had reached 9th magnitude by the time of perihelion in November. The Earth crossed the orbital plane of the comet on October 29.8 (comm. Nicolas Biver) and a dust trail was seen by imagers around this time. The comet had scarcely faded by the end of the year and was still 9th magnitude in early January. I observed it with the Northumberland refractor on January 4, when it was a diffuse object at 9.7.
The 1998 outbursts makes it difficult to predict the likely brightness at the 2004 return. It was recovered by Kenji Kadota (Ageos) in mid October at 17th magnitude, which is rather fainter than expected. It is therefore unlikely to come within visual range, unless there are further outbursts. It is worth continuing to monitor the comet, preferably by CCD. In 2005 it will be fading from its brightest of 15th magnitude and could remain observable until June, when it slips into the twilight. It retrogrades from Cancer to Lynx then resumes direct motion and reaches the border of Leo Minor and Major by the end of June.
Observations received in 1997 (60) show an uncorrected
preliminary light curve given by an initial brightening up to mid
February, peaking at 12th mag, followed by a decline of
8.1 + 5 log d + 7.5 log r
The comet was recovered at the 2006 return by several observers, including Ernesto Guido, an Italian amateur astronomer. He provides the following details:
At the end of November I started the project to try to recover the comet 71P. The first attempt was unsuccessful, probably the comet was fainter that 19 magnitude that was my limiting magnitude. On 29 December I tried again and this time I found the 71P at 7' away from the nominal position roughly at 18.5 magnitude. On 30 December I was able to obtain a second night as requested from MPC. I have received a confirmation e-mail from MPC and the circular is now out.The comet shows a linear form of light curve, with the comet brightest about 40 days after perihelion.
With the orbit approaching so closely to the Earth, an associated meteor shower might be expected, and the comet has been linked to the Tau Herculid shower, though the radiant now lies in the Bootes - Serpens region. Strong activity was reported in 1930 by a lone Japanese observer, but little has been seen since then. It is likely that any future activity would be in the form of a short-lived outburst, confined to years when the comet is at perihelion. If the fragmentation event in 1995 was sufficiently energetic some of the debris train might intersect the Earth on 2022 May 31, when dust trails from 1892 and 1897 might also be intercepted.
A. Nakamura, Kuma, Ehime, Japan, reports that a CCD image
taken low in the morning sky by K. Kadota (Ageo, Saitama, 0.18-m
reflector) on Nov. 4.84 UT shows this comet unexpectedly bright at
m_1 = 13.2, with coma diameter 0'.5 and a 0'.8 tail in p.a. 310 deg.
[IAUC 7518, 2000 November 10]
Recent observations suggest that three nuclear components of
comet 73P are now visible: what appear to be components B and C
from the observed 1995 outburst and splitting (IAUC 6246, 6274,
6301) and an apparent new component (E). Assuming that component C
(T = 2001 Jan. 27) is the primary nucleus, components B and E are
separated by Delta(T) = +0.27 and +0.74 day, respectively.
Component E was observed by K. Kadota (Ageo, Japan, 0.18-m
reflector + CCD) on Nov. 28.84 UT and by M. Jaeger (Puchenstuben,
Austria, 0.3-m reflector + Technical Pan film) on Dec. 1.19 and
2.20 -- the latter indicating that it is about 28' tailward from,
and about 1.5-2 mag fainter than, component C. Observations by
Jaeger and earlier by A. Galad and P. Koleny (Modra, 0.6-m reflector
+ CCD) on Nov. 19.19 indicate that component B is about 2.5-3 mag
fainter than component C. Jaeger adds that component C has a 20'
tail in p.a. 296 deg. Total visual magnitude estimates (cf. IAUC
7523) for component C: Nov. 25.51 UT, 11.9: (A. Hale, Cloudcroft,
NM, 0.2-m reflector; low altitude, zodiacal light); 28.84, 11.4 (S.
Yoshida, Ibaraki, Japan, 0.25-m reflector).
[IAUC 7534, 2000 December 2]
Comet 73P/Schwassmann-Wachmann 2006 The comet was recovered on 2005 October 22.49 by Carl Hergenrother. The correction to the orbit published in the 2005 comet handbook is delta T -0.43 days. A paper on the 1995 splitting of the comet by Zdenek Sekanina, together with ephemerides for the components at this return was published in the ICQ. On March 8 IAUC 8685 announced the discovery of a further 4 fragments, of 20th - 22nd magnitude, bringing the total under observation to 7.
Brian Marsden provides the list of perihelion times for the fragments [MPEC 2006-G10, 2006 April 3]:
The perihelion times (TT, 2006 June) of the components of comet 73P in chronological order are as follows: 6.95 C 7.74 Q 7.88 P 7.93 B 8.11 G 8.14 J 8.20 R 8.24 S 8.24 K 8.28 M 8.29 H 8.30 N 8.35 L 8.51 W 8.58 X 8.81 Y 8.83 T 9.02 U 9.08 VFurther minor fragments have been reported,though most are very faint; the total is now 63. Some fragments briefly reach visual telescopic brightness.
Visual observations in early March put the main fragment of the comet ('C') at 12th magnitude, with the brightest of the others ('B') at 14th magnitude. It brightened rapidly, and by early April component C had reached 10th magnitude and was easily visible in large binoculars. 'B' was reported in outburst on April 2nd, and subsequent analysis of the photometry by Giovanni Sostero suggests that the outburst began a few days previously. On April 3.95 I observed both components in 20x80B and found that 'B' was noticeably brighter than 'C', with an estimate at around 9th magnitude. Despite a bright moon they are easily visible in large binoculars from sub-urban locations.
By early May, component C was being reported as visible to the naked eye; it was well condensed with a short tail and an easy object in binoculars. Component B changes in appearance from day to day, but has generally been more diffuse. Observations show a major new outburst around May 8, making the fragment an easy object under light polluted skies. It shows quite an extreme aperture effect, being faintly visible to the naked eye, yet nearly two magnitudes fainter in 20x80B.
The fragments are (2006 May 11) near their closest to Earth at around 0.07 au (10,000,000 km). The comet fragments reach perihelion around June 7.
Meteor activity is unlikely, but the chances of encountering dust from previous returns are greatest in late May and early June. Weak displays are expected in 2022 and 2049, though details may be revised after the present apparition concludes.
Observations received so far for component C (33) give an aperture corrected
preliminary light curve of
9.9 + 5 log d + 11.1 log r
which suggests that it should reach around 5th magnitude at its brightest.
2017 In 2017 February a companion fragment, designated BT, was found, which was much brighter than the main comet. It is probably a short lived outburst. Richard Miles provides a description.
2022 The comet appeared on the PCCP as C2WPE61 and AFS015 in 2022 February. Michael Jaeger reported two new fragments imaged on 2022 July 25 at 19th magnitude, though these appeared on the NEOCP rather than the PCCP. They were designated by the MPC as 73P-BU and 73P-BV.[MPEC 2022-P18, 2022 August 2] As is often the case with the MPC, although the arc is only seven days, the orbits are given to high precision and hence give the probably false impression that the two objects are on significantly different orbits. These components soon faded, but over August 13/14 Michael and Gerald Rhemann found three new objects. These were designated by the MPC as 73P-BW, 73P-BX and 73P-BY [MPEC 2022-R15, 2022 September 2] Once again the published orbits have a physically implausible range of values. Further fragmentation is likely and Michael Mattiazzo observed the comet at 10th magnitude towards the end of October.
27 observations give an uncorrected, rather unlikely, preliminary light curve of -9.8 + 5 log d + 38.4 log r
Observations in ICQ format, last observation 2001 April 29, updated 2001 June 23.
The comet was recovered by Peter Birtwhistle (station J95) in late August 2006. An image taken by Martin Mobberley on December 16.8 showed the comet at around 15th magnitude.
The activity of the comet is showing a strong secular decline, with a drop in absolute magnitude of about 2.5 between 1993 and 2019.
Comet 78P/Gehrels Tom Gehrels discovered this comet at Palomar in 1973. Its perihelion distance is slowly decreasing and is currently around the lowest for 200 years. The eccentricity is slowly increasing, with a marked jump in both following a moderately close approach to Jupiter in 1995.2004 Juan José González reported the comet at mag 12.8 in his 20cm LX200 on 2004 August 13.14, with a small well condensed coma. I observed it at 13.3 in the N'land refractor x185 on September 18.98. Observations in November put it at 10 - 11 and it was visible in large binoculars.
Observations received in 1997 (72) don't give a very good fit
after mid February, but up till then the uncorrected preliminary
light curve is
8.2 + 5 log d +  log r
The 2004 observations (111) suggest a linear light curve of the form m = 10.4 + 5 log d + 0.0100 abs(t-T-60)
The 2011 observations (66) give an uncorrected preliminary light curve of m = 8.5 + 5 log d + 0.0180 abs(t-T-37). Taken together the observations between 1997 and 2020 are slightly better fitted by the linear form of light curve.
Comet 79P/du Toit-HartleyThe comet has passed 0.34 au and 0.60 au from Jupiter in 1963 December and 2011 September respectively. The comet will pass 0.89 au from Jupiter in 2047 May.
Comet 80P/Peters-Hartley2006 will be the fifth observed return of the comet, which was discovered in 1846, then lost until it was accidentally recovered in 1982. At its first apparition the comet was quite bright, 8-9m, which suggests that its absolute magnitude may have faded over the past 150 years. No visual observations were reported at the last return when it was expected to reach 13th magnitude, though it was observed in 1990.
81P/Wild 2 is a new comet that made a very close (0.006 au) approach to Jupiter in 1974. Prior to this it was in a 40 year orbit that had perihelion at 5 au and aphelion at 25 au. The comet was discovered by Paul Wild with the 40/60-cm Schmidt at Zimmerwald on 1978 January 6. The Stardust spacecraft visited it in 2004 and recovered material for return to earth in 2006. Only a few observations were made at the return in 1991, when it was 13m. The 2002/3 return was better and the comet peaked at around 10th mag in March.
RAS Press Release on Space Weathering on 81P/Wild
Observations received at the 1997 return give a preliminary light curve of 6.2 + 5 log d + 14.2 log r, whilst the 2009/10 return gives 6.2 + 5 log d + 13.7 log r from 8 observations.
At the 2016 return, 14 electronic observations had been received up to early 2016. These gave a very rapid brightening of the comet, which is quite different to the overall behaviour seen at previous returns. There is very little change from one apparition to the next, but there are hints of an initial rapid brightening in the observations made at previous returns, with the rate of brightening changing at around 2.4 au. In this case, there will be a rapid slow down and the comet may only reach 12th magnitude. The prediction of a rapid slow down proved correct, and the comet reached 11th magnitude in May and June and 10th magnitude in July.
Observations in ICQ format, last observation 1997 July 3, updated 1997 July 28
Observations in ICQ format, last observation 2002 December 18, updated 2002 December 24.
The comet was discovered in 1979 and observed again in 1985. But it has not been observed since that. Kazuo Kinoshita's calculation revealed that it passed close by Jupiter in 1979 and the perihelion distance reduced from 1.8 au down to 1.6 au. However, it passed close by Jupiter again in 1988, and the perihelion distance increased up to 2.2 au. It came to approach close to the sun and brighten up to 17 mag temporarily in 1979 and 1985, so it was observed. However, now that it went far away again, it reaches only to 21 mag at best.
It reached 14th magnitude in autumn 1999.
6 observations received at the 2013 return give a preliminary light curve of 12.3 + 5 log d +  log r, although the majority of these observations were made when the comet was at small phase angle and showing an enhanced brightness.
Observations in ICQ format, last observation 2000 January 26, updated 2000 August 16.
The comet was a target for the extended mission of the Deep Impact spacecraft, however Karen Meech in a press release issued in December 2007, noted that she was unable to find it. The spacecraft will now visit 103P/Hartley.
The comet had not been recovered by mid November 2008 and Carl Hergenrother provides an account of the possible reasons. Dimitry Chestnov suggests that the orbital elements of 20th magnitude NEOCP object BN24412, discovered on December 21.2 are similar to that of 85P. This object proved to be the main belt asteroid. 2008 YE2.
Following repeated failure to recover the comet, its status was changed to D/ on MPC 104395 [2017 June 9].
Comet 88P/Howell Ellen Howell discovered the comet in 1981 with the 0.46-m Palomar Schmidt. It passed 0.6 AU from Jupiter in 1978, which reduced the perihelion distance, but the biggest change to its orbit occurred in 1585 when an encounter reduced q from 4.7 to 2.4 AU. The standard light curve was not a good fit to the observations at the last return and a better fit was obtained using a linear light curve that peaked 28 days after perihelion, thus confirming the view that the comet is brighter after perihelion. The comet was never well placed for viewing in the UK at the last return and was not at the 2004 return either.
I made a tentative observation of the comet on 1998 May 29.95, estimating it at 13.5: with the Northumberland refractor. My observations prior to mid May appear unlikely and should be treated as upper limits. It seems to be another comet with a linear light curve peaking after perihelion.
Marco Goiato observed the comet on 2015 February 22.3 when it was 10.8 in his 0.22m reflector. It could brighten another couple of magnitudes, but remains a primarily southern hemisphere object.
Observations received in 1998 (24) give an uncorrected preliminary light curve of 8.9 + 5 log d + 0.0330abs(t-T-18.7); those in 2009 (69) give 1.8 + 5 log d + 42.6 log r up to 2009 December; those in 2015 (85) give 6.4 + 5 log d + 14.3 log r. There is some hint of a small outburst in July as the comet was brighter than expected from the light curve, but it soon returned to normal.
Observations in ICQ format, last observation 1999 February 6, updated 1999 April 05.
Observations in ICQ format, last observation 2004 October 15, updated 2004 December 30.
I observed it with the Northumberland refractor on September 1.88, estimating it at 13.3.
Observations in ICQ format, last observation 2002 November 2, updated 2002 December 24.
13 observations received in 2007 give a preliminary light curve of m = 8.7 + 5 log d + 18.5 log r
Observations in ICQ format, last observation 1999 April 19, updated 1999 August 12.
Observations in ICQ format, last observation 2007 November 14, updated 2007 November 18.
95P/Chiron is an unusual comet in that it is also asteroid 2060. CCD V magnitudes of Chiron would be of particular interest as observations show that its absolute magnitude varies erratically. It was at perihelion in 1996 when it was 8.5 au from the Sun and will be nearly 19 au from the Sun at aphelion in around 50 years time.
Professional observations made in South America show that the absolute magnitude reached a minimum of 7.3 in June 1999 and had risen to 5.8 in April 2001, suggesting that a period of sporadic activity was beginning. A minor outburst was reported in 2021 May.
It reached 16m when at opposition in early June 2001 in Ophiuchus. Maurice Gavin obtained images of the comet on 1999 July 10 and 11.
Observations in ICQ format, last visual observation 1999 June 12, updated 2015 February 1.
Observations in ICQ format, last observation 2002 January 9, updated 2002 January 17.
Comet 96P/Machholz in 2007 96P/Machholz should reach 2nd magnitude as it passes through the satellite coronagraph fields at perihelion in early April, however it will be 9th magnitude by the time its elongation increases sufficiently for ground based observation in late April. UK observers may pick it up in the morning sky, but it will be a fading telescopic object. The orbit is very unusual, with the smallest perihelion distance of any proven short period comet (0.13 au), which is decreasing further with time, a high eccentricity (0.96) and a high inclination (60°). Studies by Sekanina suggest it has only one active area, which is situated close to the rotation pole and becomes active close to perihelion. The comet may be the parent of the Quadrantid meteor shower.
It was a prominent object as it passed through the SOHO LASCO C3 coronagraph in early April. Juan Jose Gonzalez recovered it after perihelion on April 13.2, estimating it at 7.2 in 25x100B.
2 observations received give an uncorrected preliminary light curve of m = 13.9 + 5 log d +  log r
Observations in ICQ format, last observation 2007 April 15, updated 2007 April 16.
Comet 96P/Machholz in 2012 The comet again passed through the SOHO field of view in 2012 July. Two fragments were discovered, which probably detached at the previous perihelion passage. See the SOHO sungrazer page for details of the discovery and report on the Machholz comet complex. The first fragment was designated 96P/Machholz B, the second 2012 N1.
Marco Antônio Coelho Goiato observed it on June 17 when it was 12th magnitude. Southern Hemisphere observers may see the comet in the evening sky post perihelion.
Comet 96P/Machholz in 2017 The comet again passed through the SOHO field of view in 2017 October. Three fragments were observed, and their details are still under discussion. See the SOHO sungrazer page for details of the discovery and report on the Machholz comet complex.
Comet 96P/Machholz in 2023 The comet again passed through the SOHO field of view in 2023 January. Several fragments were observed, and their details are still under discussion. In addition a dust trail was observed in the plane of the orbit. Karl Battams provided an account of the transit, that includes an animation showing the passage of the comet. Michael Jager was able to image the comet on February 5, when it was at only 14.7 degrees elongation from the Sun. Juan Jose Gonzalez observed it on February 7.3, estimating it at 7.7 in his 20cm SCT.
Published by Jonathan Shanklin. Jon Shanklin - email@example.com