Comet C/2012 S1 (ISON) - Update 2013, Oct. 2

We obtained further follow-up on C/2012 S1 (ISON) on 2013, Oct. 1.2, through the 2.0-m f/10.0 Ritchey-Chretien + CCD + SDSS r' Filter of Liverpool Telescope (MPC code J13).

Stacking of 20 exposures, 11-seconds each, produced an image where is visible a well developed coma and tail measuring at least 3 arcmin extended toward PA  297 deg. Click on the image for a bigger version.

Below another elaboration of the same stacking. Click on it for a bigger version.

Just out of curiosity, in this ISON field there are 2 known asteroids (31176) 1997 XL9 (magnitude ~18)  & (11293) 1991 XL (magnitude ~18.5). We have highlighted here the position of the asteroids:

In the image below you can see 3 different elaborations of the ISON inner coma. The first panel on the left is a Larson-Sekanina filter.  In the middle panel elaboration with the MCM filter creates an artificial coma, based on the photometry of the original image, and subtract the original image itself in order to highlight the internal zones of different brightness that are very close to the inner core and that would normally be hidden from the diffuse glow of the comet. While the last panel on the right is the elaboration with filter RWM - 1/r theoretical coma subtraction.

Af[rho is a proxy of dust abundance within the coma. It was introduced by Michael A'Hearn et al. in 1984 (AJ 89, 579, 1984) with the aim of comparing measurements concerning the dust continuum under different observing conditions, times and instruments.

A first result obtained by CARA team from a preliminary analysis on comet ISON is shown in the  two plots below: one concerning the observed Af[rho]quantity (where  is evident an apparent peak related to the phase effect) and another with the log(Afrho) quantity corrected for the solar phase effect. Click on the images for a bigger version. 

Credit: CARA

Credit: CARA

On our data of October 01, 2013 we measured an Af[rho] value about 350 cm, for a corresponding aperture of nearly 20,000 km in diameter at the comet distance, confirming the fading trend. Click on the image for a bigger version.

For more info about comet C/2012 S1 (ISON) please see our previous post & images:

http://remanzacco.blogspot.it/2012/09/new-comet-c2012-s1-ison.html

http://remanzacco.blogspot.it/2012/10/updated-data-for-comet-c2012-s1-ison.html

http://remanzacco.blogspot.it/2012/10/comet-c2012-s1-ison-update-2012-oct-4.html

http://remanzacco.blogspot.it/2013/05/comet-c2012-s1-ison-update-may-20-2013.html 

https://twitter.com/comets77/status/376777383258234880/photo/1

UPDATE - October 05, 2013

We obtained new data on comet C/2012 S1 (ISON) on October 04, 2013. The details are on the caption of the image below.

UPDATE - October 06, 2013

We obtained new data on comet C/2012 S1 (ISON) on October 05, 2013. The details are on the caption of the image below.

UPDATE - October 07, 2013

We obtained new data on comet C/2012 S1 (ISON) on October 07, 2013. The details are on the caption of the image below.

UPDATE - October 08, 2013

Here we present a preliminary analysis with respect to a sunward facing feature detected on comet C/2012 C1 (ISON) The feature imaged between 30th Sept 2013 and 7th Oct 2013 is clearly visible and reproducible in images taken over four observing nights we had with the 2.0 m. Liverpool Telescope between these dates.

All images have the same integrated exposure time (being a sum of 20x11sec.=220sec at 2x2 binning on the CCD, yielding a pixel resolution of 0.3”/pixel.) In all image the same filter (SDSS R' band) and exactly the same false-color scale visualization using Astroart software has been deployed.

After the usual dark subtraction and flat field correction using field data provided by the Liverpool Telescope (as on some nights, automatic calibration was not performed) and stacking on the photometric centre of the coma, we built a radial normalization model of the coma suing a plug in developed for this purpose within Astroart (The plug in is known as the M.C.M. or Median Coma Model). With this , we then subtracted the modelled image from the original image data to enhance any difference between the real and the "ideal modelled" coma.

The results of this processing is shown in the four images detailed below. Each square is a zoomed in view of the full image, and each image is 30" wide, with each rectangular white grid scaled to 7.5"x10". The white pixel in the centre of each image is the brightest pixel inside the coma, known as the optocenter.

The sunward facing feature, feature shows a maximum size on data taken on the 7th Oct reaching out to about 2.7 arcsec (about 4500 km at the projected plate scale) and also is notably almost absent on data taken on the 4 Oct, which we believe is due to adverse seeing conditions on this date at our site on La Palma. The seeing conditions for each night as measured are :1 Oct/1.1" arcsec, 4 Oct/2.1" arcsec, 5 and 7 Oct. 1.5" arcsec.

At this plate scale the sunward facing feature we believe cannot be associated with any degree of confidence with any nuclear phenomenon (eg/jets) but  after careful analysis, we now believe it to be a typical cometary coma condensation. We therefore state that this feature is a cometary atmosphere feature present in almost all comets approaching the Sun and the Earth.

UPDATE - November 06, 2013

We obtained new data on comet C/2012 S1 (ISON) on November 04, 2013. The details are on the caption of the image below.

UPDATE - November 11, 2013

We obtained new data on comet C/2012 S1 (ISON) on November 11, 2013. DDP processed on the image to enhance the core of the coma and the thin second tail. The details are on the caption of the image below.

by Nick Howes, Ernesto Guido and Martino Nicolini

Comet C/2012 S1 (ISON) - Update May 20, 2013

Comet C/2012 S1 (ISON) was discovered on September 21, 2012 by Vitali Nevski and Artyom Novichonok on CCD images obtained with a 0.4-m f/3 Santel reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia.

Comet C/2012 S1 (ISON) will get to within 0.012AU of the Sun (extremely close) at the end of  November 2013 and then to ~0.4AU from Earth at the end of December 2013! According to its orbit, this comet might become a naked-eye object in the period November 2013 - January 2014. And it might reach a negative magnitude at the end of November 2013. For more info about the discovery please see our previous post here. While here & here you can read our October 2012 updates about comet ISON.

Our Team working with a suite of Hubble sized telescopes in Australia, Hawaii and the Canary Islands is collaborating with a range of professional scientists in an attempt to get high spatial resolution data on comet C/2012 S1 (ISON). Supported by the Liverpool John Moores Astrophysics Research Institute and the Faulkes Telescope Project we have been imaging C/2012 S1 ISON since the day it was  discovered, being part of the discovery MPEC for the comet ourselves.
 

Our recent images taken with the 2m Telescopes on La Palma are being worked on as part of an ongoing collaboration which started with Comet 103P/Hartley 2 with Nalin Samarasinha, a Senior Scientist at the Planetary Science Institute (PSI) in Tucson, AZ, USA. Nalin, a specialist in comets at the Planetary Science Institute, has been looking at the detailed structure of the near nucleus coma of comet C/2012 S1 ISON using data we are delivering in to the PSI. (click on the images below to see a bigger version).

 

Most recently, Nalin had looked at image comparisons for our team’s dataset from May 02, 05, and 07 taken with the F10/2m telescope on La Palma, using an extremely sensitive camera, perfectly suited for detailed comet work.

The images shown here are 28x28 pixel crops of the inner region with the optocenter (assumed to be the nucleus) at the center. (click on it for a bigger version)

"This comparison shows that the sunward feature we suspected from images taken on 02/05/2013 is originating slightly north of west and then the position angle (PA) of the feature (measured from north through east) increases as one moves away from the optocenter" quotes Nalin. The exact PA of this feature is tricky to determine, as it will depend on how far away from the optocenter that you look at and when near the optocenter, PAs can be very uncertain. Nalin's interpretation is that the curvature of this feature is not due to any rotational effects but is due to radiation pressure pushing dust grains towards the tail. Ultimately, this feature merges in with the tail.

This amazing result from a ground based set of observations, is in close agreement with features detected by the Hubble Space Telescope in images taken in April of this year. It goes to show how valuable ground based observations can be.

Credit: NASA, ESA, and Z. Levay (STScI)

As the comet comes closer to the Earth the spatial resolution will improve, and we should get more detailed views on the coma structure. Ongoing collaborations with scientists with the amateur community have been discussed in many recently published papers, and  this is a prime example of one that is delivering valuable scientific data on a hugely interesting object.

by Nick Howes and Ernesto Guido

Comet C/2012 S1 (ISON) - Update 2012, Oct. 4

We obtained further follow-up on C/2012 S1 (ISON) on 2012, Oct. 4.6, again  through the 2.0-m f/10.0 Ritchey-Chretien + CCD + Bessel R filter of Faulkes  Telescope North (F65) Haleakala.

Stacking of 9 exposures, 120 seconds each, produced an image where  a well developed and elongated coma measuring nearly 6"x9" is now visible, extended toward PA  280 deg. Click on the image below for a bigger version.

From this stacking, the Afrho parameter was determined to be about 1530  +/- 150 cm (see panel below). The total magnitude has been measured as R= 17.7. Click on the image below for a bigger version. 

For more info about comet C/2012 S1 (ISON) please see our previous post: 

http://remanzacco.blogspot.it/2012/09/new-comet-c2012-s1-ison.html 

http://remanzacco.blogspot.it/2012/10/updated-data-for-comet-c2012-s1-ison.html

by Nick Howes, Giovanni Sostero and Ernesto Guido

Updated data for comet C/2012 S1 (ISON)

Our team performed follow-up observations of comet C/2012 S1 (ISON) on 2012, Sept. 28.6, 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. After stacking 13 R-filtered exposures, 120-seconds each, comet ISON appears as a pale blob of light, slightly elongated toward the south-west (this is particularly obvious looking at the azimuthal median subtraction rendition). Click on the image below to see a bigger version.

The Afrho (proxy of dust abundance within the coma) calculation we performed on this dataset, using a few Tycho reference stars having colour indexes close to that of the Sun, provided rather puzzling results: in short, we found a significant variation of the Afrho amount, according to the dimension of the measurement window (something pretty different from the steady state coma model).

We measured an Afrho maximum value of 1365 +/- 200 cm, for a corresponding aperture of nearly 16,000 km in diameter at the comet distance. After this peak, the Afrho amount decreases, reaching a minimum of about 900 +/- 200cm for apertures of 50,000 to 60,000 km. Similar afrho values has been found analyzing CCD images obtained with the 1.5-m f/8 reflector at the Majdanak observatory on Sept. 21.99 (courtesy of A. Novichonok, scale 0.42"/px).

Afrho variation along the coma of C/2012 S1

This behaviour seems to indicate a steep photometric variation along the coma's profile, with a significant increase of the afrho values close to the central condensation (i.e. within about 6" to 8" of the nucleus), which would not be detected using average amateur telescope, for reasons of resolution and seeing conditions.

Indeed, our previous Afrho measurements, performed on Sept. 22.5 through the 0-25, f/3.4 reflector + CCD (scale 1.7"/px), provided an Afrho amount of about 600 +/- 150 cm, for a corresponding aperture of nearly 46,000 km at the current comet distance (taking into account the respective error bars, this compares rather well with the values found through the bigger scopes at similar distances from the nucleus).

From this data it seems that, at the current distance of comet ISON from the Sun, small amateur telescopes will have difficulty accounting for its near-nucleus activity, due to their unfavourable scale factor, and seeing conditions (however they still can play a role monitoring the evolution and general trend of this comet).

The punch line : Comet C/2012 S1 appears to be even more active than we first thought...watch this space!

Giovanni Sostero, Nick Howes and Ernesto Guido

New Comet: C/2012 S1 (ISON)

Cbet nr. 3238, issued on 2012, September 24, announces the discovery of a new comet (discovery magnitude 18.8) by Vitali Nevski (Vitebsk, Belarus) and Artyom Novichonok (Kondopoga, Russia) on CCD images obtained on Sept. 21.06 UT with a 0.4-m f/3 Santel reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia. The new comet has been designated C/2012 S1 (ISON). 

Comet C/2012 S1 (ISON) will get to within 0.012AU of the Sun (extremely close) at the end of  November 2013 and then to ~0.4AU from Earth at the beginning of January 2014! According to its orbit, this comet might become a naked-eye object in the period November 2013 - January 2014. And it might reach a negative magnitude at the end of November 2013.

We performed some follow-up measurements of this object, while it was still on the neocp. Stacking of 24 unfiltered exposures, 120-sec each, obtained remotely on 2012, September 22.4 from H06 (ITelescope network near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD, shows that this object is slightly diffused, with a 5" coma. The FWHM of this object was measured about 15% wider than that of nearby field stars of similar brightness.

Our confirmation image (click on the image for a bigger version):

Below a false colour rendition of our image, better showing the coma (click on the image for a bigger version):

Below you can see an animation showing the movement of the comet in about 30 minutes (click on the thumbnail for a bigger version):

M.P.E.C. 2012-S63 assigns the following nearly parabolic (e = 0.999999964) orbital elements to comet C/2012 S1 (ISON): T 2013 Nov. 28.87; e= 0.99; Peri. = 345.56; q = 0.012 AU; Incl.= 62.36. (prediscovery observations were identified by G. V. Williams in MPC data from the Mount Lemmon Survey on 2011 Dec. 28 and from the 1.8-m f/4 Pan-STARRS reflector on 2012 Jan. 28)

Below you can see the orbit (Credit JPL) and current position of comet C/2012 S1 (ISON). The comet is at present of magnitude ~18 and it is located at 6.25 AU from the Sun. 

Below you can see a graph generated using the software Orbitas and showing the predicted magnitude (in red) versus the elongation (click on the image for a bigger version):

Below a star map (calculated for Latitude is 46 deg north, time about 45 minutes before sunrise) for 2013, Nov.10. showing the comet position (click on the image for a bigger version):

While by clicking here, you'll see a daily animation from 2013, Nov. 10 to Nov. 25 (wait a few seconds for the video to load).

Ephemerides (for the geocenter) generated using the "Minor Planet Ephemeris Service" for the period November 2013 - December 2014. A word of caution: as always with comets, the future magnitudes reported here are only indicative at this stage. Next weeks will tell us something more about the future of this promising comet.

Date       R.A. (J2000) Decl.    Delta     r     El.    Ph.    m1                                                                          
2013 11 10 12 08 03.9 -01 01 00   1.003   0.768   45.3  66.5   4.9
2013 11 18 13 24 14.0 -10 43 12   0.871   0.528   32.2  86.2   2.9
2013 11 21 14 01 42.1 -14 51 28   0.856   0.423   25.3  95.1   1.9
2013 11 22 14 15 23.6 -16 13 08   0.856   0.386   22.7  98.2   1.5
2013 11 23 14 29 42.5 -17 32 40   0.860   0.346   20.1 101.2   1.1
2013 11 24 14 44 40.4 -18 48 53   0.868   0.304   17.4 104.1   0.5
2013 11 25 15 00 21.0 -20 00 30   0.880   0.260   14.6 106.9  -0.1
2013 11 26 15 16 52.8 -21 05 50   0.898   0.211   11.6 109.2  -1.0
2013 11 27 15 34 37.4 -22 02 15   0.922   0.156    8.5 110.4  -2.3
2013 11 28 15 54 44.1 -22 42 33   0.955   0.090    5.0 107.8  -4.6
2013 11 29 16 23 20.6 -20 31 20   0.985   0.022    1.3  93.0 -10.6
2013 11 30 16 22 02.5 -16 36 54   0.917   0.108    5.0 127.2  -3.9
2013 12 01 16 19 50.9 -14 12 38   0.872   0.170    7.8 128.2  -2.0
2013 12 02 16 18 02.1 -12 08 28   0.834   0.223   10.4 127.5  -0.9
2013 12 03 16 16 32.0 -10 12 48   0.801   0.271   12.8 126.3  -0.2
2013 12 06 16 13 22.7 -04 40 04   0.716   0.395   19.9 122.2   1.2
2013 12 07 16 12 40.2 -02 48 06   0.692   0.433   22.2 120.7   1.6
2013 12 08 16 12 06.2 -00 53 51   0.668   0.468   24.5 119.1   1.8
2013 12 09 16 11 39.8 +01 03 27   0.646   0.503   26.9 117.5   2.1
2013 12 20 16 13 50.5 +28 33 54   0.467   0.829   57.1  94.7   3.5
2013 12 21 16 14 41.8 +31 45 29   0.457   0.855   60.3  92.1   3.6

by Ernesto Guido, Giovanni Sostero & Nick Howes