"Debris cloud" of comet C/2010 X1 (Elenin)

"Debris cloud" of comet C/2010 X1 (Elenin)

The *big* problem imaging the "debris" of C/2010 X1 (Elenin), is the low S/N of the little cloud it left away. If you want to integrate enough, in order to increase the S/N of yours images, then you face the problem of the trailed stars that are crossing the field, producing an annoying interference with the faint cometary cloud.

A professional astronomer (CARA's collaborator Gian Paolo Tozzi, Arcetri Observatory, Italy), suggested to shoot again the field of the comet with the same instrumentation when the comet moved away, and then to subtract the field stars from the cometary original images you want to enhance. In principle, this would help to eliminate at least some part of the disturbing effect produced by the trailed stars.

We tried this interesting technique on the images we obtained on 2011 Oct. 23.37 (see our previous post), and we obtained the following result (click on the thumbnail for a bigger version):

We have still to improve this method (we found some issues matching the size of the field stars, due to the different seeing conditions and/or focus on two consecutive nights), anyway the results looks pretty promising. The image treated in this way, is significantly cleaner, and some features of C/2010 X1 (Elenin) are easier to be seen. In particular, the sunward part of the "cometary cloud" appears much sharper compared to the antisolar direction. The diffuse shape of the comet appears to be somehow "conical", about 1.5 deg long overall, with a maximum thickness of about 10-arcmin in the solar direction: the ovate shape of the "cometary cloud" than thinners tailward. We failed to find any convincing condensation within it, provided that the few "knots" visible on our image, are probably due to some noise left by the star profile removal process.

Talking about morphology, it's interesting to notice some similarities of what we found in our image, with this archive image of comet Shoemaker-Levy 9, seen after its break-up (Lowell Observatory 1.1m Hall telescope of 23 June 1993):

by Giovanni Sostero, Ernesto Guido and Nick Howes

Friday, October 21, 2011

Another recovery attempt on C/2010 X1 (Elenin)

Today, we imaged again the field of C/2010 X1 (Elenin) remotely, from the GRAS network (Mayhill station, NM). We used two scopes, nearly simultaneously: the 254mm, f/3.4 reflector + CCD, and the 0.1m, f/5 APO refractor + CCD.

The first observing session, on 2011 Oct. 21.3861 UT, through the 10" reflector (15x20sec, unfiltered exposures, scale 1.6"/px, field of view 59'x40'), provided no obvious moving objects in the field of view.

The second observing session with the APO refractor, was scheduled on two separate slots, spaced by about 2h, on 2011 Oct. 21.38392 and Oct. 21.47579. The first sequence was a stacking of 9x30sec, the second was 11x30 sec (unfiltered exposures, scale 3.5"/px, field of view 3.9 degx2.6 deg). Blinking the two fields, we found something moving on the sky background (moonlight interference).

After some image processing, to clean a bit the image, we get this result (click on the thumbnail below to see the animation):

50% crop of the original image

You can download the animation here:

http://tinyurl.com/652otdx

If this *extremely* faint and diffuse blob of light is not an artefact (stray light reflection, ghost image, etc.), it is very close to C/2010 X1 ephemerids position, and it seems to moves with the appropriate proper motion.

Tentatively we measured a 14'x8' (kind of) extremely faint cloud, elongated toward PA 300.


The provisional astrometry we obtained from these two set of data is listed below (very difficult measurement, since there isn't any obvious condensation):

COD H06
OBS E. Guido, G. Sostero, N. Howes
MEA E. Guido, G. Sostero. N. Howes
TEL 0.10-m f/5 reflector + CCD
ACK MPCReport file updated 2011.10.21 16.54.10
NET UCAC-2
CK10X010 KC2011 10 21.38392 07 55 08.81 +28 41 56.3 x.xx N H06
CK10X010 KC2011 10 21.47579 07 53 48.16 +28 45 45.0 x.xx N H06


We encourage other observers to confirm or refute this possible find we made, with their own observations/images. We suggest the use of wide-field, fast focal ratio scopes, possibly under very good sky conditions.


UPDATE October 23, 2011

Following our yesterday's report of the recovery of the remains of comet C/2010 X1 (Elenin), we confirm the detection of the "cloud" on today observations too.

Here is again the "cloud" imaged by our team few hours ago on October 23.4, 2011 remotely from the GRAS network (Mayhill station, NM) by 0.1m, f/5 APO refractor + CCD (12x300-seconds exposures). Click on the thumbnail for a bigger version:

The "cloud" is roughly 40' long with an extension of 6' near the expected position of the comet.

Here you can see an image where the X marked the ephemeris position for comet C/2010 X1 (Elenin). Click on the thumbnail for a bigger version:

And this is an animation showing the movement of the "cloud" along with to the movement of the expected comet's position (click on the thumbnail for a bigger version):

The fast streak moving on the right side of the animation is the PHA asteroid (138524) 2000 OJ8 (magnitude 14.5).

After our request to other observers to try to confirm our find, we have received the following images and animation by fellow observers that seems to confirm the presence of this faint and diffuse "cloud" moving at the same speed and PA of the comet C/2010 X1 (Elenin) very close to C/2010 X1 ephemerids position.

The image by Rolando Ligustri obtained remotely from New Mexico on October 22, 2011 (the image processing was particularly forced to highlight the faint nebulosity):

The animation by Leonid Elenin on October 22, 2011 (click for a bigger version)

The animation by Juanjo González Díaz on the evening of October 21, 2011 (click for a bigger version)

by Ernesto Guido, Giovanni Sostero and Nick Howes SOURCE

Posted in: SPACE