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: http://arxiv.org/abs/1409.7641


by Giovanni Sostero, Nick Howes & Ernesto Guido

Splitting event in comet 168P/Hergenrother

Over the past few weeks, comet 168P/Hergenrother has been under intense scrutiny due to its strange behaviour, namely a 6 magnitude surge in its brightness in a matter  of several nights. Simultaneously the central condensation became markedly brighter and  sharper, whilst the coma was also seen to grow in size. This has triggered the attention of amateur and professional astronomers alike. Most of the time these brightening events (comets are among the most  unpredictable astronomical objects from themselves) originate from some activity within, or associated with, the nucleus of the  comet. There were strong assumptions in the astronomical community on the possible emergence of some visible fragments in the coma, the potential consequences of a break-up of in the comet's nucleus.

There have even been a few claims relating to a sighting within the comet hunting community, however these turned out to be most likely false alarms, due to the unfavourable combination of seeing/instrumental  resolution within the amateur community. Our team have been monitoring the evolution of this comet with a variety of  instruments including the research grade Faulkes Telescopes, with sub arcsecond imaging capability.

Today...we found the fragment...

Our team performed follow-up observations of comet 168P/Hergenrother on 2012, Oct. 26.4, remotely through the Faulkes Telescope North (Haleakala) under good seeing conditions, and a scale of 0.3"/px.

Stacking of 13 R-filtered exposures, 30-sec each, obtained remotely, from the Haleakala-Faulkes Telescope North on 2012, Oct. 26.4, through a 2.0-m f/10.0 Ritchey-Chretien + CCD, under good seeing conditions, shows the presence of a secondary nucleus, or fragment, placed about 2" in PA 188 with respect to the main central condensation of comet 168P.

The magnitude of this fragment was measured to be R about 17, and it shows a diffuse coma nearly 2" in diameter. Click on the image below for a bigger version.

Below you can see an animation obtained by means of the same frames (here East is to the left, North is to the bottom). The animation covers about 20 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 new fragment we discovered today):

0168P        KC2012 10 26.42126 23 41 31.60 +34 07 36.5          15.6 N      F65
0168P        KC2012 10 26.42747 23 41 31.37 +34 07 44.6          14.3 N      F65
0168P        KC2012 10 26.42901 23 41 31.31 +34 07 46.6          15.7 N      F65
     168Pb   KC2012 10 26.42126 23 41 31.57 +34 07 34.5          17.2 R      F65
     168Pb   KC2012 10 26.42747 23 41 31.32 +34 07 42.3          16.9 R      F65
     168Pb   KC2012 10 26.42901 23 41 31.28 +34 07 44.3          17.4 R      F65

There was no evidence of this fragment in our previus follow-up images, obtained through the Faulkes Telescopes 2.0-m f/10.0 Ritchey-Chretien + CCD on 2012, Oct. 22.4 and Oct. 3.6, to limiting magnitude about 19.. See our previous post about comet 168P here and here.

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: http://arxiv.org/abs/1409.7641

by Giovanni Sostero, Nick Howes & Ernesto Guido

Update on Comet 168P/Hergenrother

Our team performed follow-up observations of comet 168P/Hergenrother on 2012, Oct. 22.4, remotely through the 2m, f/10 Ritchey-Chretien + CCD of Faulkes Telescope North (Haleakala) under good seeing conditions, and a scale of 0.3"/px. Comet 168P has recently undergone an outburst with its magnitude increasing from ~14-15 to magnituide ~9.5. For more info about the recent outburst of this comet, see our previous post here.

Recent observations posted on comet-images ml were showing a "cloud" of material trailing the nucleus in the anti-solar direction. In our image (stacking of 9 x 30-second exposures) is visible an unresolved and diffuse trail about 6" long and 3" wide in PA145. Click on the image for a bigger version.

Below you can see a graph showing recent magnitude estimates of comet 168P.  Click on the image for a bigger version.

Credit: Seiichi Yoshida

by Giovanni Sostero, Nick Howes, Alison Tripp & Ernesto Guido

Follow-up on 168P/Hergenrother bright phase

According to reports issued by a number of observers to several astro-forums, comet 168P/Hergenrother is currently experiencing a bright phase: over the course of several nights, it increased in brightness by several magnitudes, reaching a total visual magnitude of approximately 8. We performed some follow-up on it remotely, on 2012 Sept. 26 and Oct. 3, through the 2.0-m f/10.0 Ritchey-Chretien + CCD + Bessel R filter of the Faulkes Telescope South, at Siding Spring (click on the image below for a bigger version).

Inspecting our stacked images obtained on Sept. 26, the comet shows an obvious  central condensation, measuring nearly 3" across; the total coma was traced to a  diameter of about 1.7'. On Oct. 3, the central condensation grew to 8" and the  total coma diameter was nearly 3'. It's interesting to notice how, apart the growing of the central condensation  size, also its appearance changed, appearing pretty sharp on Sept. 26, and a bit "fluffy" on Oct. 3.

Subtracting the two images (after normalization of the stackings) of Sept. 26  from Oct. 3, the evolution of the central condensation became obvious. To some  extent, the difference might be due to a slight change in the perspective angles  (e.g. its phase angle passed from 10 to 13 deg), however we consider that a part  of what we see in the panel, is a genuine evolution of the central condensation  due to its active phase (click on the image below for a bigger version).

The photometric data supports the observed evolution: our afrho data on Sept. 26  shows a peak of about 670 +/- 100 cm at 2230 km from the photocenter, while on  Oct. 3 we measured an afrho of 1210 +/- 150 cm peaking at a radius of about 3000 km from the photocenter.  This seems to indicate a two-fold increase of the afrho  activity within the central condensation in a matter of a week, as well the  apparent recession of the activity peak from the central condensation. A change in the photometric profile of the coma is also obvious, from the comparison of the two panels, with the Oct. 3 graph significantly wider and less  steep, compared to that of Sept. 23.

  

By clicking on the thumbnail below you can see a short animation of comet 168P/Hergenrother on our images of 2012 Sept. 26:

So our follow-up confirms and adds scientific data to the previous reports: currently comet 168P/Hergenrother is alive and rather active.

Giovanni Sostero, Nick Howes, Alison Trip and Ernesto Guido