New Comet: P/2011 W2 (RINNER)

Cbet nr.2922, issued on 2011, November 29, announces the discovery of a new comet (discovery magnitude 17.9) by Claudine Rinner on CCD images obtained on November 28, 2011 taken with a 0.5-m f/3 reflector located at the Oukaimeden Observatory near Marrakech, Morocco. The new comet has been designated P/2011 W2 (RINNER).

We performed some follow-up measurements of this object, while it was still on the neocp. Stacking of 14 unfiltered exposures, 120-sec each, obtained remotely, from the GRAS Observatory (near Mayhill, NM) on 2011, November 29.3, through a 0.25-m, f/3.4 reflector + CCD, shows that this object is a comet: diffuse coma nearly 15-arcsec in diameter.

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

M.P.E.C. 2011-W80 assignes the following preliminary orbital elements to comet P/2011 W2: T 2011 Oct. 10.62; e= 0.51; Peri. = 210.50; q = 2.32 AU; Incl.= 14.20

Congratulations to Claudine Rinner for this new amateur comet discovery!!

by Ernesto Guido, Giovanni Sostero & Nick Howes

COMET P/2010 UH55 (SPACEWATCH)

Cbet 2923, issued on 2011, November 30, reports that an apparently asteroidal object reported by the Spacewatch survey and designated 2010 UH55 by the Minor Planet Center last year, has been found to show cometary activity. H. Sato (Tokyo, Japan) first reported the appearance of a condensed coma of size 6"-8" on 2010 Nov. 17.4 UT. Sato's report remained unconfirmed until the past month, when he again found the object on 2011 Nov. 3.5 to show a cometary appearance. Other observers have confirmed the cometary nature of this object. The new designation is P/2010 UH55 (SPACEWATCH).

Prompted by an alert note of Dmitry Chestnov, we performed some follow-up about this object. Stacking of 5 R-filtered exposures, 40-sec each, obtained remotely, from the Haleakala-Faulkes Telescope North on 2011, November 28.6, through a 2.0-m f/10.0 Ritchey-Chretien + CCD, shows that this object is a comet: diffuse coma about 9" in diameter, and a faint, broad tail, nearly 20" long toward west-northwest. Total magnitude m1 R about 18.2

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

M.P.E.C. 2011-W82 assignes the following orbital elements to comet P/2010 UH55 (SPACEWATCH): T 2011 May 10.36; e= 0.58; Peri. = 221.62; q = 2.77 AU;  Incl.= 8.67


Giovanni Sostero, Krzysztof Rochowicz, Ernesto Guido and Nick Howes

2005 YU55 - Close Approach

On November 08, 2011 at 23:28 Universal Time (UT), the Near-Earth asteroid 2005 YU55 passed within 0.85 lunar distances (or 319,000 km or 0.00217 AU) from Earth's surface.

Asteroid 2005 YU55 was discovered by Robert McMillan during the Spacewatch survey on December 28, 2005. The 2011 approach is the closest that we know about in advance by an asteroid with an absolute magnitude this bright since 2010 XC15 (H = 21.4) approached within 0.5 lunar  distances in 1976 (although astronomers did not know about this flyby at the time), and until 2028, when 2001 WN5 (H = 18.2) will approach within 0.65 lunar distances.

The object has been previously observed on April 2010 by Mike Nolan, Ellen Howell and colleagues with the Arecibo radar on April 19-21, 2010 and shown to be a very dark, nearly spherical object 400 meters in diameter with a relatively long rotation period, 18 to 20 hours. 


Trajectory of Asteroid 2005 YU55 - November 8-9, 2011. Click on the thumbnail to see a bigger version:

(Credit: NASA-JPL)

We have been able to follow-up this object on November 09.25 remotely from the GRAS Observatory (near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD. At the moment of our observing session the asteroid was moving at about 260.07 "/min and it was of magnitude ~11. The image below is a single 60-second exposure (click on it for a bigger version).

While this is an animation showing the object movement in the sky. Each image was a 2-second exposure. Click on the thumbnail to see a bigger version:

Scientists working with the 70-meter Deep Space Network antenna at Goldstone, California, have generated a short movie clip of asteroid 2005 YU55 from data  collected on November 07, 2011. These are the highest-resolution radar images ever obtained for a near-Earth object:

Due to its size and proximity to Earth, the Minor Planet Center has designated 2005 YU55 as a "Potentially Hazardous Asteroid". Although classified as a potentially hazardous object, 2005 YU55 poses no threat of an Earth collision over at least the next 100 years, the entire interval over which its motion can be computed reliably.

For more info about this close approach:

http://www.skyandtelescope.com/observing/home/133013563.html

http://echo.jpl.nasa.gov/asteroids/2005YU55/2005YU55_planning.html

https://www.nasa.gov/mission_pages/asteroids/news/yu55-20111108.html


by Ernesto Guido, Giovanni Sostero and Nick Howes

Recovery of comet 171P/Spahr

On October 19.5, 2011 we started an observing session to recover the periodic comet 171P/Spahr. T. B. Spahr (then at University of Arizona, Arizona, USA - now Director, Minor Planet Center) discovered this comet with the 0.41-m f/3 Schmidt telescope in the course of the Catalina Sky Survey on 1998 November 16.39.

We found an object of magnitude ~20.6 with the following offset from the nominal position of comet 171P (RA 2.5'W  DEC 0.6'S). We found again the same object on October 20.5 & October 24.5. A faint possible tail, about 20-arcsec long toward North-East is visible. We imaged it remotely with the 2.0-m f/10 from the Siding Spring-Faulkes Telescope South.

Below you can find our recovery image of October 24, 2011:

While below you can see an animation showing the movement of the comet (click on the thumbnail for a bigger version):

Before our recovery, comet  171P/Spahr was last observed on February 06, 2006.

by Ernesto Guido, Giovanni Sostero, Nick Howes & Antoni Kasprzyk

New Comet: C/2011 U2 (BRESSI)

Cbet nr.2875, issued on 2011, October 26, announces the discovery of a new comet (discovery magnitude 19.4) by Terry H. Bressi on CCD images obtained on September 24, 2011 with the Spacewatch 0.9-m f/3 reflector at Kitt Peak. The new comet has been designated C/2011 U2 (BRESSI).

We performed some follow-up measurements of this object, while it was still on the neocp. Three stacked 60-s R-band exposures taken remotely on Oct. 25.5 with the 2.0-m f/10 "Faulkes Telescope North" at Haleakala show that this object is a comet with a compact coma about 4" x 3" in size, elongated toward p.a. 250 deg, with a sharp central condensation and a tail about 20" long in p.a. 250 deg.

Our confirmation image (click for a bigger version):

M.P.E.C. 2011-U85 assignes the following preliminary orbital elements to comet C/2011 U2: T 2012 Oct.  9.20; e= 1.0; Peri. = 222.89; q = 2.49 AU; Incl.= 9.81

by Ernesto Guido, Giovanni Sostero, Nick Howes & Daniel Cirelli

"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):

UPDATE OCTOBER 25, 2011

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

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):

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