Friday, October 4, 2013

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

An interesting update with new pictures of Comet ISON.

Via, 2 October 2013  (Thanks Connie)

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:

by Nick Howes, Ernesto Guido and Martino Nicolini

1 comment:

Linda said...

What does it all mean - requiring more brain power than is currently accessible by my weary state....anyone? Oh, btw, I love playing with words, and sometimes I believe we are left really obvious clues. Here's one that came to me the other night while drifting off, almost asleep, which made me wake up laughing - here 'tis: the word is comet = com-ET isOn! (said in Southern US dialect) hehe. Well, I amuse myself.
Hope you're all doing fine over there in USA folks! Much love.