MISSION 29P – Centaur comet observing campaign news

Latest outburst: 2023 03 21.17 ± 0.17 17.10R => 16.16R

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March 21

We have had a 0.9-mag eruption within the last 24 hours, the first for some 28 days. Follow-up observations are encouraged.

March 18

Latest photometry shows a continual fade having now reached almost magnitude 17.1R. There is a good chance that a new mini-outburst will happen in the next few days.

February 28 – Example of archived observational data

Here is an example of the summarised epoch data corrected for differences in measuring aperture size starting just after the latest outburst of 2023 February 21.5. We have 664 observation lines in total this apparition with a few months to go before it ends. So far there are 3018 observation lines in the main spreadsheet.

Note that the  data listed in Columns A to R are derived from the first line of observational data, the whole series of which have been averaged in Columns S to Y, the latter corrected for photometric aperture size.

Here as an example are the individual lines of source data around the time of the 2023 02 21.50 outburst:

February 24 – Two strong outbursts separated by 57 days

The last two strong events have been these:

Outburst at 2023 02 21.50 ± 0.23 16.82R => 14.40R
Outburst at 2022 12 26.73 ± 0.07 16.40R => 14.20R
Time difference = 56.77 ± 0.25 days

Although this time may be indicative of the same source erupting after one rotation of the nucleus, the outburst comae in the two cases appear rather different:

February 22 – JWST successful shortly before a new outburst!

JWST has has taken 8 x 525 sec spectral ‘maps’ (0.6 – 5 micron, resolution ~100) of the central 3 arcsec region (resolution ~0.1 arcsec) at 2023 February 20.14-22 when the nucleus was in its low activity state.

29P never switches off completely since gas and dust escape and maintain a weak coma at all times. So JWST will probe the immediate environment whilst the nucleus was in that low state.

Denis Buczynski, observing from Portmahomack, Scotland, has subsequently discovered that 29P has had a strong outburst reaching about 14.3R ~30 hours after the JWST’s observations. Here is recent photometry showing this:

0029P KC2023 02 21.20830 06 17 09.51 +28 41 33.1 16.87R 718 5.11″ (5.48″) 3x60s Wiggins

**Outburst at 2023 02 21.50 ± 0.23 16.80R => 14.3R (provisional)

0029P KC2023 02 21.79288 06 17 05.42 +28 40 44.4 14.2 R I81 5.15″ (5.66″) Rc 5x60s Buczynski
0029P C2023 02 22.03407 06 17 03.81 +28 40 27.5 14.41R XXX 5.40″ (5.58″) 120s 0.5-m T72 Miles
Confirmation was possible thanks to the use of iTelescope’s facilities in Chile.

Especially interesting is the fact that the last time 29P outburst so strongly was on 2022 December 26.73±0.23 when it reached 14.20R. The gap between these events is 56.77±0.25 days showing yet again the persistence of the 57-58 day periodicity in its strong outbursts, indicative of the rotation period of the nucleus.

February 19 – JWST to observe 29P on 2023 02 20.14 to 20.22

James Webb Space Telescope is scheduled to observe 29P/SW1 starting at 2023 February 20 at 03:20 UT and ending around 05:18 UT. It will use the NIRSPEC IFU instrument that captures 900 simultaneous spectra over most of its 0.6–5.3 μm wavelength range where NIRSPEC is sensitive. The total area mapped comprises a square just 3 arcsec x 3 arcsec centred on the nucleus. Each element of the array measures just 0.1″ x 0.1″.

It is rather disappointing that 29P has been fading and it looks like it will be essentially quiescent when JWST takes a look and so we may not discover so much of what lies behind its bizarre behaviour. A large proportion of the hypervolatile gases that power its sudden eruptions travel at speeds of 0.3-1.0 km/s and so with JWST’s window opening 5.7 days after its last eruption there will be time enough for these to disperse.

On the other hand, one characteristic of 29P/SW1 is that it steadily outgasses through the crust, which process maintains a faint coma at all times. It is this environment that JWST will probe. Here is the overall lightcurve to date, with the last datapoint some 8 hours prior to the start of JWST coverage. 29P is clearly quiescent so the findings should be a fair representation of the object in its low state of activity. Click here for the latest plot and observations.

February 18

Deep image showing mini-outburst coma from February 14.42 event

February 15

Another mini-outburst about 0.7 mag amplitude has just taken place. Timing is very accurate owing to the fact that observations were made from iTelescope’s T30 0.5-m aperture instrument at Siding Spring whilst the event was unfolding!

We also have 2.0-m images taken from Siding Spring just 2 hours after the start of the event.

Coverage was very good thanks to Denis Buczynski in Scotland, Guy Wells in England, Patrick Wiggins in Utah, iTelescope facilities in Utah and Australia (used by Richard Miles), the Faulkes Telescope South, and Wayne Hawley in England, who confirmed the sudden rise in brightness just 6 hours after the initial eruption.

February 12

Fade continues 14 days since last significant event. Updated plot below with latest contributions.

February 5

Faint asymmetric outburst coma about 7 days post-outburst. Thanks to Wim Cuppens we have this view of the new outburst coma despite the strong moonlight present:

January 29

New outburst discovered by Jean-François Soulier earlier today. More information to come. See latest lightcurve plot below.

January 27

Here is a view of 29P immersed in its outburst coma most of which has originated from the strong outbursts of last November 21, 27 and 29. It was taken earlier today. The outer edges of the coma extend virtually to the edge of the 10′ square frame especially in the south direction.

January 21

Just 7 days have elapsed for the next event to take place, a mini-outburst of amplitude 0.6 magnitude r 1.7 nucleus-equivalents. Patrick Wiggins imaged it faint on January 19.11 whilst Adrian Jones imaged it bright at January 19.76, constraining mid-time to January 19.43.

January 13

Another outburst has been picked up some 17 days after the previous. Amplitude is just 1.3 mag so we may expect a further event soon.

January 11

29P has faded and to reach its steady-state quiescent state at around 17.05R in a 2.5″ radius measuring aperture. Unfortunately, a stellar occultation on January 09 near the southern California border with Mexico coincided with bad weather near San Diego and so far no reports have been received. In the last 5 or 6 days observations have been affected by strong moonlight, which has now come to an end so it will be a good time to watch out for mini-outbursts over the coming days.

End of 2022 update

Centaur 29P reached opposition on 2022 December 30.4 in the constellation of Auriga at a phase angle of 1.02°. We have detected 19 outbursts during the pre-opposition period, of which 8 have been strong eruptions (amplitude >1.0 mag or 4 nucleus-equivalents). The weak outbursts appear to represent a different phenomenon and recently we have witnessed few eruptions of intermediate intensity. The object is now well placed in the evening sky for close monitoring and our objective now is to have sufficient coverage to detect outbursts that are particularly faint. Of course we never miss any strong outbursts, which is testimony to the dedication of all our observers.

December 28 – One positive observation of December 27 occultation

Although the weather conspired against most observers in the USA, Vadim Nikitin south of Roswell, New Mexico recorded a ~3.4 s (62-km) disappearance close to the predicted centreline despite clouds threatening to block his view.

New strong outburst ahead of December 27 occultation

Discovered by Denis Buczynski from north-east Scotland, this event has been narrowed down in time to around 10 hours ahead of the occultation. We have received some excellent reports from observers confirming the outburst and showing it shining at magnitude 14.2R with the new outburst coma reflecting almost 15 nucleus-equivalents of sunlight. Postscript – Artyom Novichonok has observations from Uzbekistan which constrain the time of outburst further.

Preparing for the 2022 December 27.52 occultation

This event may prove to be the best this decade so observers please do try and cover it. It involves a 13th magnitude star and high accuracy predictions are available from the Lucky Star team. A video record, preferably with absolute timing, is required. Frame exposure times of 0.25 sec or shorter are recommended. The chart below is from Mike Kretlow’s Collaborative Occultation Resources and Archive (CORA). Current weather forecast indicates that the north-western part of the track north of the Grand Canyon will be plagued by cloud and some rain. New Mexico and Texas look to have clear skies early on the Tuesday morning. Predicted mid-times are:

12:20:12 UT San Antonio, TX; 12:20:22 UT Odessa, TX; 12:20:35 UT Socorro NM, and 12:20:42 UT Sanders, AZ. 

Occultation Success!

Bob Jones has made an initial report of a disappearance lasting 3.3 s from a location -17.7 km from the predicted centreline.
Norman Carlson was particularly lucky to record a short 1.5 s positive from +10.3 km off the centreline.

An initial look at these observations and those of a previous occultation seen from Cerro Pachón, Chile show they are consistent with a spherical body some 59-60 km in diameter. By some strange law of chance we have another favourable event on Dec 27.52 when 29P occults a 13th magnitude star as seen from very north of California, southern Nevada, central New Mexico and western Texas. This will be the best opportunity from N. America for many years to come. Here is a preliminary profile based on the December 19 observations:

December 19 update

Thanks to 1.0-m multi-filter imaging by André Debackère using the Las Cumbres Observatory network, we now have the BVRI magnitudes of the occulted star and that of 29P measured in a 5.8″ radius aperture seen <12 hours before the event. Patrick Wiggins has also imaged 29P just 4 hours ahead of the due time showing a slight fade of 29P to 16.3R in a 5.5″ radius photometric aperture. A total occultation will see the V or R light drop by 3.6 mag in an 11″ diameter aperture and 3.9 mag drop in a smaller 5″ one  Here also is the latest 1.0-m colour image showing the star to be occulted.

occstar C2022 12 19.00083 06 43 51.06 +29 28 12.3 14.27B Z31
occstar C2022 12 19.00189 06 43 51.05 +29 28 12.3 13.23V Z31
occstar C2022 12 19.00299 06 43 51.07 +29 28 12.4 12.67R Z31
occstar C2022 12 19.00404 06 43 51.06 +29 28 12.3 12.09I Z31

0029P C2022 12 19.00299 06 44 06.59 +29 28 08.1 16.18R Z31 5.45″ (5.85″) Debackere
0029P C2022 12 19.00083 06 44 06.65 +29 28 08.2 17.50B Z31
0029P C2022 12 19.00189 06 44 06.63 +29 28 08.2 16.67V Z31
0029P C2022 12 19.00404 06 44 06.55 +29 28 08.1 15.63I Z31 NET USNO-B1.0

December 18 update

A mini-outburst has taken place 1.92 ± 0.25 days ahead of the occultation. The amount of material lofted into space by the event is equivalent to a projected area of 0.4 nucleus-equivalents. There is a chance the occultation record will contain evidence of some of this material, a significant fraction of which should fall back onto the nucleus within 2-4 days. Here’s the photometry:

December 19.49 stellar occultation information

An exceedingly rare stellar occultation of a 12th magnitude star by the nucleus of Comet 29P, the track of which passes over populated areas, is due between 11:44-11:55 UT on 2022 December 19 (Sunday night/Monday morning).

Mike Kretlow of CORA (Collaborative Occultation Resources and Archive) has provided these details:

Occultation Date + Time : 2022-12-19 at 11:49:22 UT +/- 0.06 min
Object Designation : 29P/SW1
Star Designation : GDR3 3386666379589120128
Star Coordinates (ICRF) : RA = 06 43 51.06, DEC = +29 28 12.1
Star Magnitudes : G = 12.94 mag, RP = 12.24 mag, BP = 13.48 mag
Object Magnitude : R = 16.6 mag (assuming no further outburst)
Estimated Magnitude Drop : 4.5 mag in R
Estimated Max. Duration : 3.6 sec
Object Mean Diameter : 64 km
Speed of the shadow : 17.7 km/s
Elongation to Moon & Sun : 115° (sunlit = 20%), Sun = 166°
Cross-track uncertainty : 5.9 mas = 21 km = 0.36 path-width (1-sig)

Mike has made available an interative map here:

December 15 UPDATE: The Lucky Star team observed a 29P occultation of a faint star on December 05 and this has led to a further improvement in the known orbit of the nucleus. Details including an iterative map can be found here:


The occultation is predicted to cross Taiwan during Sunday evening (~11.54-11.55 UT on December 19, viz. night of Monday, December 19/20 local time):

Earlier around 11.44-11.46 UT the path of the shadow track crosses close to the U.S. / Mexico border visible in the early morning sky Monday. The following maps depict the ground track with the Lucky Star one now indicating a southwards shift of around 60 km. In practice the uncertainties in the position overlap significantly.

Observers many km away from the predicted track may detect attenuation of the star by a debris disk created by this comet’s outbursts. There is evidence that the nucleus is unusually spherical in shape and so observers are encouraged to obtain a video record of the event since this will readily test this inferred shape without the need for absolute timing accuracy.

December 13

More 2.0-m images thanks to the Comet Chasers Group:

December 12 — ALERT! Very favourable forthcoming stellar occultation on early morning of Monday, December 19

Here is a view of the evolved coma over 12 days after the last outburst, obtained by Jean-François Soulier last night from his robotic ’29PREMOTE’ observatory in Dauban, Haute Provence, France (L27). The pseudo-nucleus is now fainter than 16.0R, which bodes well for the forthcoming stellar occultation visible near the U.S.-Mexico border on 2022 December 19.49 involving a magnitude 12.2R star. High-precision astrometry updated to a few weeks ago and a recent occultation event has narrowed the uncertainty in the N-S track position shown below to a mere ±25 km (1 σ). N.B. The current JPL K192/76 ephemeris has the orbit displaced some 1300 km to the North of the actual orbit.

December 2

We have now obtained 2.0-m images taken earlier today by Mike Beer and Valentina Matei in good conditions after a long spell of bad weather, etc. The coma appearance is a composite result produced by the recent 3 strong outbursts.  The grayscale image was taken almost 11 days after the initial major outburst and has been subjected to a logarithmic stretch to show the coma as it might appear visually through a very large telescope. The blue-white images are the same stack of 12 frames but subjected to a 15° rotational gradient filter using IRIS software and depicted in false colour. One noteworthy feature of the outbursts triggered by the initial event of Nov 22 is that a strong outflow is directed towards p.a. 30°, which is almost the opposite direction to the direction of mass flow from the initial event.

December 1

Here’s an update showing the lightcurve depicting the third outburst and its subsequent evolution.

November 30

Here is the latest lightcurve for the current apparition with still one month to go before 29P reaches opposition. We have now entered a particularly revealing episode in the revival of intense activity that started in 2021 September. The brightening of November 29 that we observed within ~3 hours of the start of the outburst appears to have been rather short-lived – something that might have been missed in the past. More observations needed!

Thanks to Alison Tripp of the Faulkes team, I have now downloaded some November 26 2.0-m images taken by Errol Simpson. Here is the image-processed result, which should allow us to extrapolate to a more accurate time-zero:

November 29

Another weaker outburst has just been detected thanks to 1.0-m imaging by Ben Wooding at St Mary’s School, Bridgend.

Although the small brightening is immersed in a strong outburst coma, the extent of the change is still equivalent to a ‘strong’ outburst, roughly equal to 30 nucleus-equivalents and so we should see a more complex expanding cloud of ejecta as a result. Dave Storey from his Isle of Man observatory has images taken around Nov 29.16-29.17 and these look to have been taken around the start of the latest event so we have a good fix on the time it began.

Image processing of the latest 1.0-m exposures from Las Cumbres Observatory, Chile show the ejecta released in these last two outbursts of Nov 27 and Nov 29. The following false-colour picture has most of the circularly symmetric coma subtracted and thereby reveals the new expanding coma outflows close to the nucleus, which fan out mainly in a northwards direction. 


November 27

New strong outburst  from about 14.1R to 12.2R detected thanks to Denis Buczynski’s measures:

0029P KC2022 11 27.88355 06 53 43.02 +29 20 01.7 12.22R I81 5.15″ (5.66″) 3x60s Rc
0029P KC2022 11 27.88571 06 53 43.00 +29 20 01.4 12.19R I81
0029P KC2022 11 27.88786 06 53 42.91 +29 20 01.8 12.05R I81
0029P KC2022 11 27.89002 06 53 42.91 +29 20 01.8 12.20R I81

Confirmed by Wayne Hawley – See observations listed halfway down this page.


Here is an excellent processed result using 22 frames with a 0.4-m instrument from François Kugel in Haute Provence. Notice the excellent correspondence of the features in the outburst coma with those shown in the 2.0-m image below. The pixel size of the two instruments was 0.83″ vs. 0.27″ with the larger telescope.

November 25

We are now starting to see fine detail in the expanding debris cloud. Here is the latest from the Faulkes Telescope North reproduced to the same image scale as the similar processed image dated 2022 Nov 23.63, i.e. exactly 2 days earlier:

November 24

Coma expanding but no sign yet of a further outburst. Here is a higher SNR image obtained by Cai Stoddard-Jones along with an image processed close-up version in false colour that reveals an intense condensation travelling outwards towards p.a. 330° approx, the centre of which has displaced 3.0 arcsec. equivalent to 11,500 km or 75 m/s, whereas the outer edge of the near-spherical debris cloud has reached 56,000 km, i.e. a maximum expansion velocity of 360 m/s.


November 23

First close-up of the expanding outburst coma thanks to André Debackère. Notice the characteristic ‘Pac-Man’ shaped cut-out at position angles of 0° to 60°, which suggests that the direction of the outburst projected on the sky was in p.a. 210° approx.


Patrick Wiggins is to be congratulated for imaging Centaur comet 29P hours after a very intense outburst. Here is the last measurement prior to, and the first measure following the strong outburst, which has attained magnitude 11.95R.

0029P C2022 11 21.34482 06 55 51.60 +29 16 21.2 15.69R 718

0029P C2022 11 22.32544 06 55 34.15 +29 16 54.6 11.95R 718

The outburst has been confirmed by Denis Buczynski:

0029P KC2022 11 22.83770 06 55 24.76 +29 17 11.1 11.95R I81
0029P KC2022 11 22.83986 06 55 24.73 +29 17 11.1 11.92R I81
0029P KC2022 11 22.84201 06 55 24.64 +29 17 11.7 11.94R I81
0029P KC2022 11 22.84417 06 55 24.64 +29 17 11.1 11.94R I81
0029P KC2022 11 22.84632 06 55 24.59 +29 17 11.4 11.95R I81

Lightcurve plot below updated.

November 21

Remarkably, Denis Buczynski has picked up a rebrightening just 2.5 days after the last event. Thankfully, Patrick Wiggins’ skies were clear last night and so his data confirm the 12th outburst event this apparition with opposition still more than 5 weeks away (Dec 30). Nick James’ data just received also confirm the event, the intensity of which is 1.1 nucleus-equivalents.

I have updated the plot below. It appears that mini-outbursts may be much more common than previously thought.

November 20

A further small outburst of about 1.1 mag amplitude occurred on Nov 18.26, first detected by JF Soulier. Confirmed using Las Cumbres Observatory 0.4-m network. Interesting that these two latest outbursts took place only about 30 hours apart. The reduced magnitude plot (see below) has been updated.

Here is a stack of 10 images taken by Patrick Wiggins about 2.3±0.5 days after this outburst. It shows the outflowing ejecta directed towards position angles (p.a.) 0° to 40° approx.:

Created with GIMP

November 17

A new outburst event has been detected – the 10th this apparition, of which we have now completed one-third. Although the latest mini-outburst this morning exhibited a 0.18 mag amplitude in the standard aperture, when measured in a 1.7 arcsec radius aperture, the amplitude increased to 0.35 mag (17.53R => 17.18R).

The additional new outburst coma equates to some 35% of the area of the nucleus alone, which represents the intrinsically weakest event detected during the past 20 months.

Patrick Wiggins, after discovering a Type 1a supernova (SN 2022aaiq) on November 15 has, with his 29P images of November 17, confirmatory evidence of this latest mini-outburst. His observations are a little earlier too, which means we can tighten up on the timing precision plus also recognise that the event looks to be of 0.21 mag amplitude or 41% of the nucleus-equivalent area. Thanks Patrick!

November 10

A further 2.0-m image today has confirmed a further small brightening in what appears to be a second mini-outburst of about 0.30 mag amplitude on 2022 11 10.39 +/-0.16.

Eric Watkins has confirmatory observations from iTelescope’s T21 (H06) as well as Jean-François Soulier last night from L27 (29PREMOTE).

November 09

We are fortunate to have managed a single 60-sec exposure on the 2.0-m Faulkes North today that has revealed the occurrence of a mini-outburst (probably sometime yesterday) ejecting a new coma equivalent to 0.6 times the area of the nucleus. 29P is currently close in the sky to a nearly full Moon making accurate photometry with small scopes difficult.

November 01

Photometric observations are shown plotted below. The Rc magnitudes have been corrected to the standard photometric aperture radius of 5.7 arcsec and corrected for heliocentric distance, distance from Earth, and for phase angle assuming a linear coefficient of 0.035 mag/deg. As well as the 7 distinct outbursts with amplitudes ranging from 0.5-2.2 mag detected this apparition, there may be other mini-outbursts that have maintained some low-level activity. Opposition occurs on December 30.

October 22

A slow fade has set in. Thanks to Faulkes Telescope Project time, 12 x 60s exposures were obtained showing the outburst coma morphology after 7 days. The Faulkes Telescope North imaged r’ and i’ filters simultaneously and these 24 frames have been stacked in the attached, which also shows galaxy MCG +05-17-005 magnitude 15.2B.

October 13

Denis Buczynski has discovered a medium-strong outburst that probably occurred on October 12. Confirmed by Nick James.

Image from a stack of 18x60s images shows the outburst coma after 2 days at mag 15.0R and slightly diffuse compared with stars in the field.

September 27

The next AAS Division of Planetary Sciences meeting is due to take place in London, Ontario, Canada between October 2 – 7. Richard Miles will be attending and presenting an iPoster.

N.B. You have to be registered to see the iPosters once the meeting starts but you can do this as a ‘virtual’ participant thereby avoiding having to travel there. You can also participate in the meeting, hear the talks and make comments if you are registered virtually. Here is a screendump of what the 29P iPoster looks like – click on image for larger version:

September 24

We’ve detected an outburst of about 0.9 mag amplitude, which equates to an increase in coma intensity of 6 nucleus-equivalents.

Here is what the outburst coma looks like after nearly 4 days’ expansion, with a very distinctive north-south asymmetry:

September 16

Here is an image processed stack of 16 x 60s exposures taken by Errol Simpson with students from King Fisher Lake School, Tofo Village, Inhambane Province, Mozambique, and their Science Teacher Aaron Catrett (Faulkes Telescope Project) with the 2.0-m FT North six days after the latest outburst. The image in blue-white false colour has been subjected to a 20° rotational gradient filter using IRIS software and shows the main outflows of outburst ejecta. The red pixel marks the position of the comet nucleus. This is an example of the use of a large telescope to follow up outbursts discovered by amateurs. Here we see a single main outflow directed towards p.a. 340°. It is hoped that documenting the various outbursts over several years it will be possible to identify a number of sources on the nucleus as well as the spin characteristics of the nucleus.

September 14

We are 5 days on from the latest 1.5 magnitude outburst and here’s a detailed view of the expanding coma showing the presence of an outflow at p.a. 300°-345° taken using the 2.0-m Faulkes North instrument:

September 10

Again, thanks to the Faulkes Telescope Project for detecting a second strong outburst this apparition, amounting to an amplitude of a little over 1.5 mag and attaining 15.0R. A 99.8% illuminated Moon was in the sky when images were obtained.

September 8

Thanks to the Faulkes Telescope Project and in particular Paul Roche for providing telescope time, and to teacher, Ben Wooding of St Mary’s School, Bridgend, Wales, we have a detailed image of the 4-day-old outburst coma showing a distinct outflow at p.a. 0° – 30°. This exemplifies the objective of MISSION 29P: that is to follow up discoveries of outbursts by amateur observers with much higher resolution imaging to better understand the processes taking place within the inner coma and at the nucleus. The main direction of flow relates to the position of the source, possibly a cryo-geyser, on the nucleus.

Status report as of September 6

Peculiar Centaur object 29P has now reached a solar elongation of 64° in the morning sky and so has become more accessible to observers operating in the early hours. Observations began on July 16 and we have already seen 2 mini-outbursts and one strong outburst. Amateur observers have provided excellent monitoring and record coverage of the start of its apparition, better than anything achieved in the past. New observers are invited to join the campaign since we aim to secure accurate R photometry 24/7. Please refer to the detailed Tutorial on Observing 29P, or alternatively make your FITS images available and the photometry will be done for you.

First strong outburst of the new apparition

August 18 has seen a medium-intense outburst, the first since the 2022 February 11 outburst that reached magnitude 15.05R. That’s a gap of some 188 days between strong events, one of the longest intervals we have witnessed. Below is an animation of this strange object in outburst as three 240-sec exposures made with the LCO 0.4-m (T04) on Haleakala, Hawaii as of 2022 August 18.62.

More observations encouraged !


New apparition 2022-23 has commenced !

Thanks to  Jean-François Soulier (L27, C10) and Luca Buzzi (204) we now have the first series of observations of this object low in the morning sky. There does not appear to have been any strong outburst in recent weeks because of the absence of any extended coma. The observing gap whilst the comet was in conjunction with the Sun was a mere 52 days, a record short gap in our data!

MISSION 29P Observer Statistics for 2021-22

Here is a full breakdown of observers contributions for the latest completed apparition – a record number of contributors  – Well done everyone!

Centaur comet 29P and the James Webb Space Telescope

JWST Proposal 2416 entitled “Measuring Volatile Production in Active Centaurs with NIRSpec” led by Adam McKay (PI) is due to kick off between 2022 July 25 – July 31 by observing 22nd magnitude 39P/Oterma with its Integral Field Unit (IFU). Four further targets will be investigated before finishing with 29P during 2023 Feb 09 – Mar 30, i.e. about 3 weeks either side of its retrograde point. The methodology is similar for all targets when NIRSpec will map H2O, CO2 and CO in a 3″x3″ box centered on the nucleus as well as an offset from the nucleus to characterise the coma. Methane may also be detected if the observing epoch is shortly following an outburst. A total of 3.1 hours will be spent observing the nucleus and around 29P between 0.6-5.3 microns (resolving power ~100). The 3″x3″ box is traversed by 30 slits providing high spatial resolution. Pointing accuracy of JWST is 0.1″.
(added on 2022 Jun 18)

End of the 2021-2022 Apparition

We have finally reached the end of our coverage of the latest apparition.

Patrick Wiggins (Obs Code 718) has extended observational coverage well into the month of May, with his last time series taken on May 21 when 29P could be seen at almost 17th magnitude, sitting just 21 degrees from the limb of the Sun!

I believe this is a record for a comet so faint as 29P at the moment and just 26 days from solar conjunction.  Patrick has also imaged the field containing the comet on May 25 with the Sun 18 degrees distant and just 5 degrees altitude. The target appears to be fainter than mag 16.0R, the plate limit.

So 29P last exhibited a ‘strong outburst’ 214 days since its last one: that reached magnitude 13.1R on October 23. It appears that the historical record of 4 rapid consecutive outbursts last September has possibly resulted in a significant loss of sub-crustal pressure and that the centaur object is taking a long time to build up this pressure ahead of the next strong event. Maybe it will still be quiescent when we next see it appear after conjunction with the Sun on 2022 June 16? Coverage of the new apparition could begin around July 12 at the earliest.

Clear skies for then!

Latest lightcurve of 29P

Here are plotted the R magnitude of the comet during the current apparition. The measurement is expressed in terms of the brightness of a 5.7 arcsec radius photometric aperture. Inner coma measurements are also shown (in red) made with a 1.6 arcsec radius aperture with either 1.0-m or 2.0-m telescopes.

2021 December 21 occultation event – Report

Only one observer (Peter Ceravolo) was able to make a video recording of this potential occultation event, which was negative. Other observers were defeated by the very bright Moon nearby, the very low temperatures causing equipment malfunction, or by cloud.

Hubble imaging of Comet 29P

Hubble’s Wide-Field Camera (WFC3) is working again and has secured images of 29P on November 23, November 30 and December 7.

The first set of 10 exposures were obtained 10-12 hours after a small outburst. Here’s a preview of one of the Dec 7 frames.

Have included an inset showing roughly the same patch of sky taken with the 1.0-m at Macdonald Obs. in average seeing.





(Write-ups about 29P by Dr Tony Phillips appear on the October 15 page and on the October 26 page of the Spaceweather website)

Strong outburst at 2021 10 23.75 +/-0.03  15.70R => 13.15R

Mini-outburst (below) of 0.35 mag amplitude on 2021 10 16.88 +/-0.01 captured by Jean-Francois Soulier (France), Kritti Sharma et al. (GROWTH, India), and Tim Lister (LCO, Tenerife)

Our 5th successful outburst lightcurve !

Latest images:

(click on images for full resolution)

Peering inside the expanding coma.

The outburst coma from the October 16.88 event can be seen expanding as a fan-shaped outflow close to the nucleus at p.a. 0 – 90 deg or so.



The following two images, the colour one from Peter Tickner, indicate that there is an excess of blue light in the upper right of the coma (p.a. 270-350 deg). This may be evidence of the emission of light from ionised gas moving in this direction and overtaking the slower-moving dust. Thanks Peter.


Latest Observations:

STOP PRESS – Fourth outburst on 2021 09 27.6+/-0.2 almost 9 times greater intensity than the first two events !!!!

STOP PRESS – Third outburst on 2021 09 27.0 almost 5 times greater intensity than the former two events. Time between each pair of outbursts ~20 h

LATEST: An outburst of about 2.5 mag amplitude appears to have occurred on 2021 September 25.34 +/-0.005 followed about 20 hours later by another outburst of similar intensity

Thanks again to Patrick Wiggins (718) imaging from Utah and a good run of clear skies, and Denis Buczynski in Scotland also favoured with clear skies these past two nights, we have witnessed a double outburst, where one presumably has subsequently triggered another cryo-eruption (see listing of observations below). These two events might herald more intense activity in the coming few years. The last 2.5 years have only witnessed 8 events brighter than mag 14.5R, which coincides with similar relatively quiescent behaviour seen earlier when the comet was halfway around its orbit of the Sun, i.e. two seasons earlier. If the nucleus has a high tilt then these quiescent times may correspond to the seasons when the poles are directed towards the Sun (and Earth). Since the equatorial regions on the nucleus experience the greatest amount of solar radiation, these are likely to be more thermally processed and hence exhibit more intense cryovolcanicity. Watch out in the coming year or two for 12th magnitude outbursts.

An earlier outburst of the current apparition was detected by JF Soulier on August 25. It exhibited an outburst amplitude of 2.4 mag and subsequent imaging using the 2.0-m Faulkes Telescope North has revealed structures in the expanding inner coma.

Here’s the appearance of the coma on September 8, showing the new event as a brighter inner coma whilst the edge of the outer coma has continued to expand at 0.22 km/s:

The present 2021-2022 apparition began with the first observations reported by Jean-François Soulier on June 25 at a solar elongation of 29° in the morning sky. That means that the comet hid from us when too close to the Sun for just 13% of the time – a new record!

Previous apparition

The 2020-2021 apparition is now over with a record 338.5 days of coverage, the longest such coverage of any apparition and also the most observing epochs achieved (1168). The observers who contributed were:

The following image is the last one taken this apparition with the comet at only 19° solar elongation. It is not detected which means it was fainter than magnitude 16.0R at that time.

29P appears to have had a mini-outburst of 0.9 mag amplitude whilst at 25° solar elongation. Here’s the image:

Patrick Wiggins observing from Utah has confirmed the mini-outburst, his observations yielding a magnitude of 15.74R.

Two very weak mini-outbursts occurred during March. They were each of just 0.11 magnitudes amplitude reaching 16.9R:

With many dedicated observers following 29P, we get a much more reliable evaluation of small brightness changes even though it is now 17th magnitude. This is a good demonstration of the benefit of having more observers. For the first 11 days of coverage, the intrinsic trend due to varying distance and phase angle is expected to be a fade of 0.018 mag. However on March 17.46 +/-0.28 there looks to have been a step-change of 0.11 mag (red datapoints). This is the smallest mini-outburst that we have detected.

Recent images:

The following two images were taken at almost the same time. The one on the right is unfiltered. You can see extra coma further from the nucleus than can be seen in the r’-filtered image on the left. The reason for this may be that the nucleus has been almost quiescent during the past 30 days with little debris ejected far into space since most of it falls back. So what does escape is gas from sublimating hypervolatile ices and it is the emission lines from the gas that adds to the coma brightness far from the nucleus.

We know that the main gas species is carbon monoxide and most CO+ emission lines appear at wavelengths shorter than the passband of the r’ filter (550-690 nm). Also nitrogen (N2+) emission is mostly at the blue end of the spectrum Unfiltered images should pick up these faint gaseous emissions as can be seen in Jean-François Soulier’s image on the right. In future, using the new MuSCAT3 camera on the FT North, it should be possible to look for colour changes in the coma following weak outbursts. This will be particular so if the comet remains largely quiescent close to opposition.

See plot below also showing how data from several observers monitoring the comet allows us to detect small outbursts. We’ve had a couple of such events as shown in these plots:


Thanks to Jean-François Soulier (L27, Haute-Provence, France) and Nick James (970, Chelmsford, UK) who independently discovered the comet going into outburst. Thanks to Nick’s timely alert we have obtained the best coverage ever of one of this comet’s outbursts. Here is a plot of the data from L27 showing the outburst lightcurve analysed in terms of the G magnitude using a 10″ radius photometric aperture. A video of this outburst has been prepared by Jean-François.

Another outburst also took place less than 6 days later on 2020 November 25.45±0.24 with the magnitude going from 15.3R to 14.3R

29P reached opposition on November 6 and so now appears in the early evening sky making it an excellent target for northern hemisphere observers. Located in Aries at a declination of +24 degrees, the comet is visible for a couple of hours after sunset between now and the end of April.

Here below is the final light-curve for 2020-2021 showing its activity during this apparition up to April 24. Click on the plot if you want to see the full-size image. There have been two very strong outbursts: one on July 26 and a second on November 19, i.e. separated by 2 x 57.9 d in time – Note the link with the nominal periodicity of 57.71 d reported in 2016, strongly indicative of the same source outbursting after two rotations of the nucleus. Minute-by-minute coverage of the November 19 event was achieved largely thanks to Jean-François Soulier’s dedicated 29PREMOTE observatory. More on those findings later. Jean-François was also successful in catching the start of the August 22 event. In all we now have outburst lightcurves spanning the first few critical hours for FOUR events namely in 2017, 2019 and 2020(2).

In addition to strong outbursts, the nucleus has exhibited at least 24 mini-outbursts some of which have been so weak that there have been 5 instances where a large fraction of the ejecta have, after several days, fallen back onto the nucleus. This happens because the nucleus is very large (approx. 64 km across) and so has a relatively high gravity and high escape velocity (approx. 20-25 m/s). Our detailed observations are revealing this collapse of the inner coma – a behaviour unique to this body! We might indeed consider 29P not to be a comet but instead a unique Transition Object that was once a TNO.

Observational data in MPC format

Full archive datasets


Observatory Code / Observer / Location /Instrument / Photometric aperture in arcsec

This list of observatories/people whose work has contributed to the current Observing Campaign between 2014 February and 2022 April. Text shown in red requires checking.

N.B. A complete list of observers contributing this present apparition beginning on 2022 July 16 can be found halfway down this webpage.

203 G. Galli, S. Foglia Italy 0.36-m f/5.76 Schmidt-Cassegrain 5.5
204 L. Buzzi, A. Aletti Italy 0.36-m f/6.5 reflector 4.8/6.0; Italy 0.84-m f/3.5 reflector 5.6
204 L. Buzzi TEL 0.84-m f/3.5 Newtonian reflector, no filter, 5.58″ (3pix)

213 R. Naves, M. Campas Spain 0.30-m f/10 Schmidt-Cassegrain 10.0 square; Spain 0.30-m f/9 Schmidt-Cassegrain 5.4
323 P. Camilleri, J. Oey, R. Miles Australia 0.40-m f/5 reflector (Perth)
718 P. Wiggins Utah, USA 0.35-m f/7 Schmidt-Cassegrain 5.2
970 N. James England 0.28-m f/10 Schmidt-Cassegrain 5.2/5.8 check
A06 E. Cortes Spain 0.25-m f/3.6 Schmidt-Cassegrain 10.0 square
B74 J. M. Bosch Spain 0.40-m f/10 Schmidt-Cassegrain 10.0 square
B96 E. Bryssinck Belgium 0.4-m f/3.8 Astrograph 5.0
C10 J.-F. Soulier France 0.30-m f/3.8 Newtonian 6.5, 4.9
C10 J.-F. Soulier TEL 0.30-m f/3.8 Newtonian reflector, no filter, 4.86″ (3pix) 6.48″ (4pix)

C35 J. Aledo Spain 0.4-m f/3.4 Reflector 10.0 square

C42 Q. Ye (Zwicky Transient Facility) Xingming, China 0.50-m ?

C77 A. Mantero Italy 0.25-m f/4 Reflector 6.7
D09 P.-J. Dekelver Belgium, 0.30-m f/4 Newtonian 4.84″ 4-pix

C90 L. Tremosa Spain 0.30-m f/5 reflector 10.0 square

E94 J. Drummond N.Zealand 0.35-m f/10 Schmidt-Cassegrain 5.9; 0.41-m f/5.2 Newtonian 7.2; 0.41-m f/4.5 Newtonian 6.0
G40 J. Tuten, N. Paul Slooh Canary Isles 0.43-m f/6.8 Dall-Kirkham 5.0
H06 N. James New Mexico 0.43-m f/4.5 5.8; A. Watkins New Mexico 0.43-m f/4.5 5.8; M. Mobberley 0.50-m T11, P. Manteca 0.50-m T11, E. Herman T11

I41 Q. Ye (Zwicky Transient Facility) Palomar, USA 1.20-m f/2.5

I64 A. Jones England 0.19-m f/5.2 Maksutov-Newtonian + Rc filter 5.6
I81 D. Buczynski Scotland 0.35-m f/6 Schmidt-Cassegrain 5.2
I88 J. Carrillo Spain 0.36-m f/5 reflector 10.0 square
J01 J. Gonzalez Spain 0.15-m f/6 Ritchey-Chretien 10.0 square
J22 K. Hills La Palma 0.50-m f/2.9 astrograph 5.9, 10.0 square
J24 J. F. Hernandez Spain 0.4-m f/10 Schmidt-Cassegrain 10.0 square
J38 F. Garcia Spain 0.25-m f/8.1 Ritchey-Chretien 10.0 square
J47 G. Muler Lanzarote 0.30-m Schmdt-Cassegrain 6.1

J69 D. Briggs England 0.30-m f/5.4 Newtonian 6.5
J77 R. Miles England 0.35-m f/8 Schmidt-Cassegrain + r’ 5.4 also V, B, Clear
L27 J.-F. Soulier TEL 0.25-m f/3.5 Newtonian reflector, no filter, 4.48″ (3pix) 5.96″ (4pix)

K01 A. Watkins England 0.35-m f/7.7 Schmidt-Cassegrain 6.2
K02 P. Carson England 0.32-m f/5.4 Dall-Kirkham 5.5/6.5
K14 M. Morales Spain 0.25-m f/5 Newtonian 5.7, 10.0 square
K60 J. Warell, Sweden 0.25-m f/6.1 SCT 5.88 6.30

L27 J.-F. Soulier France 0.25-m f/4 Newtonian reflector 6.0 (6.7)
Q38 M. Mattiazzo Australia 0.28-m f/6.3 Schmidt-Cassegrain 5.5
Q67 P. Camilleri, J. Oey, R. Miles Australia 0.32-m F/8.8 RCOS 5.5
Q68 P. Camilleri, J. Oey, H. Williams Australia 0.30-m f/3.0 reflector 7.4; P. Camilleri, J. Oey Australia 0.34-m f/5.9 SCT
W88 K. Breedlove, J. Tuten, A. Hale Chile 0.35-m f/11 Schmidt-Cassegrain (Slooh) ???
W96 J.-F.Soulier, A.Maury, J.-B. de Vanssay Chile 0.4-m f/5.2 Ritchey-Chretien 6.4
Z08 E. Bryssinck, Oria, Spain 0.70-m f/6 reflector (remote) 5.2 r’

Z09 W. Hawley, England 0.25-m f/10 Schmidt-Cassegrain 5.5

Z08 J. Warell SAAF, Oria, Spain, 0.43-m f/6.8 CDK

Z08 E. Bryssinck, Oria, Spain, 0.7-m f/8 Ritchey-Chretien 

Z10 P. Carson, Spain 0.32-m f/5.4 Dall-Kirkham 5.5
Z30 D. Storey, England 0.35-m Ritchey-Chretien 5.9
Z39 A. Acosta, Lanzarote 0.23-m Schmidt-Cassegrain 10.0 square
Z42 J. Savage, England 0.35-m f/7.7 Schmidt-Cassegrain + V 5.5, 7.9
Z74 F. Soldan, Spain 0.20-m f/6.7 Schmidt-Cassegrain 10.0 square

Z80 G. Wells, D. Bamberger, England 0.25-m f/8 Ritchey-Chretien 6.7

Z85 T. Angel, Spain 0.35-m f/11 Schmidt-Cassegrain 5.6

Z92 A. Pratt, England 0.28-m f/3.3 Schmidt-Cassegrain 5.25

XXX C.S. Morris, California, USA 0.406-m f/6.8 Schmidt-Cassegrain 4.84

XXX T. Haymes, England 0.28-m f/5.5 Schmidt-Cassegrain 5.6
XXX R. Sargent, England 0.35-m f/7 Schmidt-Cassegrain 5.04 6-pix

Las Cumbres Observatory / Faulkes Telescope Project (R. Miles, A. Hale):

A major contribution to this ’24/7′ comet monitoring activity have been the observations from the Las Cumbres Observatory global network of telescopes. Access to this network has been made available thanks to the Dill Faulkes Education Trust, and to Dr Paul Roche of the Faulkes Telescope Project based at Cardiff University, Wales assisted by Alison Tripp.

E10 coj 2m0a Siding Spring-FT South 2.0-m f/10 Ritchey-Chretien 5.4
F65 ogg 2m0a Haleakala-FT North 2.0-m f/10 Ritchey-Chretien 5.4

K91 cpt Sutherland A S. Africa 1.0-m f/8 Ritchey-Chretien 5.5
K92 cpt Sutherland B S. Africa 1.0-m f/8 Ritchey-Chretien 5.5
K93 cpt Sutherland C S. Africa 1.0-m f/8 Ritchey-Chretien 5.5

Q63 coj Siding Spring A Australia 1.0-m f/8 Ritchey-Chretien 5.5

Q64 coj Siding Spring B Australia 1.0-m f/8 Ritchey-Chretien 5.5
V37 elp McDonald Observatory A Texas, USA


Seasonal Plot 2002 – 2022 with optimised period fit:

Note that one orbit of the Sun earlier a very roughly similar pattern was evident.

N.B. Mini-outbursts are largely shown in red/pink.

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