Friday, November 2, 2012

Follow-up of splitting event in Comet 168P

Following our team's detection of a fragmentation event with comet 168P/Hergenrother on October 26, 2012, we requested via the Faulkes Telescope Education project that further observations be taken. Today, two UK Schools using the Faulkes Telescope kindly assisted in obtaining additional observations for us. The two schools (Queens College and the Dollar Academy)  performed follow-up observations of this comet on 2012, Nov.  2.4, remotely through the 2m, f/10 Ritchey-Chretien + CCD of Faulkes Telescope North (Haleakala).

Stacking of 26 R-filtered exposures, 35-sec each, obtained remotely, from the Haleakala-Faulkes Telescope North on 2012, Nov. 2.4, through a 2.0-m f/10.0 Ritchey-Chretien + CCD, under good seeing conditions, confirms the presence of a secondary nucleus, or fragment, now placed about 3.3" in PA 165 with respect to the main central condensation of comet 168P. This fragment is now fainter, compared to our previous Oct. 26.4 detection, having R magnitude about 18.7; its diameter is still about 2", but now it appears more diffuse, without a clear central condensation (this hampers a precise determination of its photocenter). This fragment appears to have developed its own tail, nearly 4" long in PA 113 (about parallel to the main tail originating from the central condensation of 168P).

Below you can see our rendition of today imaging session. Through some image processing, the tail of the fragment became easily visible. Click on the image for a bigger version.

Below you can see an animation obtained using the school's imaging frames. (North to the top, East to the left). The animation covers about 25 minutes in total. Click on the thumbnail for a bigger version.

Below you can find the astrometry lines (0168P: main nucleus of comet Hergenrother, 168Pb the fragment):

0168P        KC2012 11 02.42647 23 39 40.15 +36 23 36.3          15.2 N      F65
0168P        KC2012 11 02.43576 23 39 40.11 +36 23 45.3          15.4 N      F65
0168P        KC2012 11 02.44505 23 39 40.02 +36 23 54.1          15.9 N      F65
0168P      b KC2012 11 02.42647 23 39 40.28 +36 23 33.4          18.8 R      F65
0168P      b KC2012 11 02.43576 23 39 40.19 +36 23 42.5          18.6 R      F65
0168P      b KC2012 11 02.44505 23 39 40.10 +36 23 51.8          18.8 R      F65

A blog entry (posted on their blog on Oct 31st) by the WIYN telescope group, who were testing the new ODI instrument, showed the comet with the fragment clearly. Below you can see their image obtained on October 30. 

Credit: WIYN Observatory/ODI Instrument

Our team would like to thank Queens College and The Dollar Academy (Adam Shannon) for their superb observations and we have included them in our submissions to the minor planet centre (PI at each school) and will reference their inclusion in our ongoing project to look at the dust/continuum values of this very interesting cometary event.

UPDATE - November 03, 2012

After the publication of our post with the discovery image & info of the splitting of comet 168P, the news spread and some of the largest telescopes in the world were pointed to the comet. On JPL website has just been published this image captured by the 8.1m NOAO/Gemini North telescope on Nov. 2, 2012 at about 6 a.m. UTC and showing in great details the near nucleus area and "at least four distinct pieces".

Credit: NASA/JPL-Caltech/NOAO/Gemini

UPDATE - November 06, 2012

Below you can see our rendition of a series of images obtained by Maui Community College on 2012 November 03, through the 2-meter Faulkes Telescope North. Click on the image for a bigger version.

The fragment we found Oct. 26 appears increasingly weak and undefined, while it is maintaining its tail. A second fragment, observed by the Gemini North, is possibly visible in this image too, though he is just above the noise level of the image. Please see the following image (image processing by Mauro Facchini).

After some significative image-processing, in the stacking below there might be some evidence of a possible third fragment, tailward of the previous two (about 13" in PA 120 respect the central condensation of the comet); however its reality has still to be confirmed, due to its low signal/noise in the original images, so further follow-up on it it's needed to confirm or discard its presence.

Today the "Istituto Nazionale di Astrofisica" (National Institute for Astrophysics), or INAF for short published a short summary of the splitting event with an interview with our team's Giovanni Sostero on the 168P comet story (in Italian).

UPDATE - November 07, 2012

Comparison of two consecutive sets of images counting, respectively, twelve R-filtered exposures, 70 seconds each, and fourteen R-filtered exposures, 60 seconds each, obtained remotely (by G. Sostero, K. Rochowicz, P. Phelps, N. Howes, E. Guido), from the Haleakala-Faulkes Telescope North on 2012, Nov. 7.43 and Nov. 7.45 under not good seeing conditions, through a 2.0-m f/10.0 Ritchey-Chretien + CCD, shows that the fragment we reported on Oct. 26.4 and Nov. 2.4 now is not visible anymore (limiting magnitude about 20).

On today's stackings, we noticed, instead, the possible presence of a second, extremely weak, fragment, having R about 19.5, placed nearly 8.4" in PA 142 respect to the main central condensation of 168P. This second fragment appears to be visible, in nearly coincident positions, also on images obtained by R. Stevenson through the Gemini North telescope on 2012, Nov. 2.25 and on stackings obtained by the Maui Community College at the Haleakala-Faulkes Telescope North on 2012, Nov. 3.3. Due to its extreme faintness, we were prevented to calculate any reliable astrometric position for it, on the stackings we obtained today.

Moreover the central condensation today appears a bit fuzzy and wider compared to four days ago (see image below; click on it for a bigger version). We will perform further follow-up to verify that this evolution is genuine, and not an effect of temporary bad seeing conditions.

UPDATE - September 30, 2014

Paper by Z. Sekanina (JPL) about comet 168P fragmentation has been published on Arxiv with acknowledgement to our discovery and mention to this blog:

To read and download the full paper:

by Giovanni Sostero, Nick Howes & Ernesto Guido


Anonymous said...

congratulations , good job ..

¿ you are calculated the speed of separation from principal nucleus ?

Erik Bryssinck said...

congratutaltions with this work !! fragment has a magnitude fainter then 18! not easy to catch inside the coma of tha min nucleus!
well don!

NickAstronomer said...

Thank you Erik

Unknown said...

So, is it heading for the sun? Or already `been there done that'...?

Team said...


In one week (Oct. 26.4 - Nov. 2.4) the separation of the main fragment from the central condensation passed from 2" to 3.3", so its drifting speed respect the nucleus of the comet appears rather slow, even if we take into consideration that during the same time the comet has receded by about 6.6 Million Km from Earth, then introducing a "squeezing" effect due to the line of sight.


Team said...


The comet has already passed its perihelion distance (minimum separation from our star) on Oct. 1. That date, does incidentally coincides with the peak in its lightcurve.