Showing posts with label C/2010 X1 (Elenin). Show all posts
Showing posts with label C/2010 X1 (Elenin). Show all posts

Monday, October 24, 2011

"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):


Below you can see a new elaboration of the previous image (click on the thumbnail for a bigger version):

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:

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):

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
   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

Tuesday, October 11, 2011

C/2010 X1 (Elenin) post solar conjunction recovery attempt

Recently we tried to image C/2010 X1 (Elenin) after its solar conjunction. The observing conditions for this comet are currently quite difficult: very low in the morning sky at twilight, within the zodiacal "light pollution".

Anyway we decided to go with several robotic scopes, operating under excellent sky conditions (New Mexico and Mauna Kea). At first we aimed at the expected comet's position (MPC ephemerids) on 2011, Oct 09.5, through a 0.25-m f/3.4 reflector + CCD and, nearly simultaneously, through a 0.10-m f/5 APO refractor + CCD, from the Global Rent a Scope facility (near Mayhill, NM).

Stacking of a number of images, we observed no distinct evidence of the comet within about 30 arcmin of the expected position, with a limiting magnitude around 17, and to limiting magnitude about 15, within about 2 deg from the expected position. Below you can see the crop of the 0.25-m reflector stacked image set (click on the image for a bigger version):

On 2011, Oct. 10.6, we imaged the area where comet Elenin was supposed to be, through the 2.0-m f/10.0 Ritchey-Chretien + CCD of Faulkes Telescope North (Mauna Kea, Hawaii). Stacking several exposures, with limiting magnitude at around 20.5, doesn't show any trace of the comet within the 10'x10' field of view centered on the comet's ephemerids (while stacking these images along the proper motion of the field minor planets, we can easily distinguish the asteroid (43629), with its magnitude at 20.3 (click on the image for a bigger version):

by Ernesto Guido, Giovanni Sostero and Nick Howes

Thursday, March 31, 2011

Comet C/2010 X1 (Elenin)

According to the current ephemerides, comet C/2010 X1 (Elenin) promises to became a nice binocular object at the end of next summer. As for many new comets, there is still some discussion about the maximum brightness this comet might actually reach.

In order to provide further elements to the discussion, on 2011, March 14 we dedicated a few observing hours to C/2010 X1, using a couple of scopes kindly provided by the Tzec Maun Foundation: a RCOS 16" Ritchey-Chretien + CCD (located near Mayhill, NM) and a Takahashi TOA-150 f/7.3 refractor + CCD (located near Moorook, Australia).

We used V and R photometric filters, and a selection of different calibrated reference stars (Tycho catalogue). The first analysis indicate a compact coma about 15 arcsec in diameter; within such aperture, we measured the following magnitudes: V= 16.7, R= 16.5, with an uncertainty about 0.5 magn in each color (photometry of faint comets is always a tricky business, so this data must be taken anyway with a certain amount of caution).

The afrho parameter (proxy of the dust abundance within the coma) measured through an R-bessel filter, is close to a value 100 cm. Considering that the comet was about 3 Au from the Sun, this seems to indicate a relatively active object. It is always very risky to extrapolate the behavior of a newly discovered comet, expecially if it has a long period orbit, however we can say that, if its trend will continue this way, we might expect indeed a nice comet a few months from now. Probably a key factor will be the efficiency of water ice sublimation within the nucleus, that is expected to rise significantly in the next few weeks, when the comet will approach our star.

When the first visual estimations will be available, it would be possible to prepare a more reliable forecast about C/2010 X1 brightness peak.

Our image of C/2010 X1 (Elenin) (click for a bigger version):

by Giovanni Sostero and Ernesto Guido (CARA, AFAM)