C/2011 L4 (PANSTARRS)

DEPARTED

Type: Hyperbolic Perihelion date: 10 March 2013 Perihelion distance (q): 0.3 Aphelion distance (Q) : n/a Period (years): n/a Eccentricity (e): 1.00 Inclination (i): 84.2 JPL orbit diagram COBS lightcurve Richard Wainscoat, Institute for Astronomy, University of Hawaii, reported to the MPC that an object discovered on four CCD images taken with the 1.8-m "Pan-STARRS 1" telescope at Haleakala on 6 June 2011 appeared to show slight non-stellar appearance; three follow-up 30-s r-band exposures were then acquired by M. Micheli and Wainscoat with the Canada-France-Hawaii Telescope on Mauna Kea (queue observer Lisa Wells) on 7 June, showing that a coma is definitely visible with a subtle hint of a faint tail towards p.a. 60 deg. After posting on the NEOCP astrometrists confirmed the cometary nature. Visual observations began in March 2012, when the comet was a stellar 14th magnitude, but by May it had developed a coma, and it was around 12th magnitude by mid year. It continued brightening relatively quickly and by September was 10th magnitude. Some observers reported an outburst in August, but this was not apparent in the mean light curve. It was recovered after solar conjunction on 24 December by Alexander Amorim, when it was magnitude 8.1 in his 0.18m reflector. It soon became clear that the rate of brightening had slowed. By 2013 February it had reached 5th magnitude. It continued brightening and by the end of the first week of March had reached 0th magnitude according to observations by Marco Goiato. Nicolas Biver comments that it is one of the dustiest comets observed, with disproportionately high dust compared to its water vapour sublimation rate. Observations (VEMag = visual equivalent magnitude) Date 10x10 mag Error VEmag Coma ' 28-Jan-13 8.94 0.03 5.9 2.1 30-Jan-13 8.78 0.03 5.0 2.3 02-Feb-13 8.87 0.02 5.8 2.0