New update on comet C/2011 L4 (PANSTARRS)

Comet C/2011 L4 (PANSTARRS), discovered by Pan-STARRS 1 telescope on Haleakala, Maui, on the night of 2011, June 5-6, will reach perihelion in March 2013 when it will be located only 0.30 AU from the Sun and might become a bright naked eye object ( with a peak magnitude of anywhere from +1 to -1). At its brightest C/2011 L4 will appear only 15° from the Sun.

The comet is now at 3.2 AU from the Sun (m2 ~ 14.0). While visually C/2011 L4 is at m1 ~ 11.

We performed some follow-up measurements of comet C/2011 L4 remotely from the Siding Spring-Faulkes Telescope South on 2012, September 10.4 through a 2.0-m f/10.0 Ritchey-Chretien + CCD. Below you can see our follow-up image (click on it for a bigger version):

Below you can see the lightcurve of comet C/2011 L4 (PANSTARRS) collected by Seiichi Yoshida on his comet webpage: 

                                  (Credit: Seiichi Yoshida)

As a comparison, below you can see our image of the comet taken on June 7.4, 2011 just one day after his discovery by Pan-STARRS Survey. The comet was then at 8.2 AU from the Sun (m2 ~ 19.5).

While below there is our image taken on May 18.6, 2012 with the comet at 4.6 AU from the Sun (m2 ~ 15.6).

Here you can read our full past reports about this comet:

http://remanzacco.blogspot.it/2011/06/new-comet-c2011-l4-panstarrs.html

http://remanzacco.blogspot.it/2012/05/update-on-comet-c2011-l4-panstarrs.html


by Ernesto Guido, Kris Rochowicz, Nick Howes & Giovanni Sostero

Update on comet C/2011 L4 (PANSTARRS)

Comet C/2011 L4 (PANSTARRS) was found by Pan-STARRS 1 telescope on Haleakala, Maui, on the night of 2011, June 5-6. At the moment of discovery the comet was at a distance of nearly 7.9 AU from the Sun (discovery magnitude 19.4). According to his orbit, around perihelion in March 2013 the comet would be located only 0.30 AU from the Sun and might become a bright naked eye object ( ~ magnitude 1). For more info about the discovery of this comet, see our previous post on this blog of 2011, June 09.

We performed some follow-up measurements of comet C/2011 L4 remotely from the Siding Spring-Faulkes Telescope South on 2012, May 18.5 through a 2.0-m f/10.0 Ritchey-Chretien + CCD. The comet is now at 4.6 AU from the Sun (m2 ~ 15.6).  Below you can see our follow-up image (click on it for a bigger version):

It's interesting to notice a very compact coma, this means active dust production even at 4.6 AU away from the Sun (very good news). The image processing shows an asymmetric coma, probably due to a line-of-sight effect. According to our previous experiences, the "jet-like" structures evidenced by the rotational-gradient  filtering, shows very likely the striking asymmetry of the coma/tail, instead of a genuìne activity due to the outgassing of the nucleus (that we are unlikely to resolve, at this time). This idea is confirmed by the appearance of the comet through the two other algorithms we applied, the azimuthal median subtraction and the 1/r theoretical coma subtraction. 

Anyway, our R-filtered image (that are showing mainly the dusty coma) shows that comet Panstarrs is pretty active, even at such big distances from the Sun (this is a good sign for future expectations on a bright comet, next year).

by Giovanni Sostero, Ernesto Guido & Nick Howes

New Comet: C/2011 L4 (PANSTARRS)

IAUC nr.9215, issued on 2011, June 08, announces the discovery of a new comet (discovery magnitude 19.4) on four CCD images taken with the 1.8-m "Pan-STARRS 1" telescope at Haleakala, on images obtained on 2011, June 6.4. The new comet has been designated C/2011 L4 (PANSTARRS).

After posting on the Minor Planet Center's 'NEOCP' webpage, this object has been found by several CCD astrometrists to show cometary appearance. We performed some follow-up measurements of this object while it was still listed in the NEOCP. Stacking of 14 unfiltered exposures, 180-sec each, obtained remotely on 2011, June 07.4 from the Tzec Maun Observatory (near Mayhill, NM) through a 0.35-m f/3.8 reflector + CCD, shows that this object is slightly diffused, with a hint of elongation toward the north-east.

Our confirming image (click for a bigger version):

M.P.E.C. 2011-L33 assignes the following preliminary orbital elements to comet C/2011 L4: T 2013 Apr. 17.12; e= 1.0; Peri. = 331.67; q = 0.36 AU; Incl. = 104.74

According to this very preliminary orbit based on an arc of only 2 weeks, this comet might become a bright object ( ~ magnitude 2) around perihelion in March-April 2013 and better placed for southern hemisphere. Next weeks will tell us something more about the future of this comet!!

This is the second comet discovery for PANSTARRS.

by Giovanni Sostero & Ernesto Guido