186P/Garradd (0186P)

Type: Periodic Perihelion date: 27 March 2019 Perihelion distance (q): 4.4 Aphelion distance (Q) : 5.6 Period (years): 11.1 Eccentricity (e): 0.12 Inclination (i): 28.8 JPL orbit diagram COBS lightcurve G. J. Garradd (Siding Spring Observatory, New South Wales, Australia) discovered this comet on images obtained on 25 January 2007 using the 0.5-m Uppsala Schmidt and a CCD camera. The three images indicated a magnitude of 18.0-18.3. In late February, M. Meyer (Germany) announced that he had found three prediscovery images on Siding Spring Observatory Digital Sky Survey images from 1975 and 1996. He had been slightly adjusting the early orbits that were calculated when he found an image of the comet on a plate exposed on 26 February 1996. The magnitude was given as 17.8. The orbit improvement brought about by this position then enabled Meyer to locate the comet on images exposed on 31 May and 3 June 1975. The magnitude on these images was given as 15.5. In linking all of these positions, G. V. Williams (Central Bureau for Astronomical Telegrams) found that comet images reported on IAU Circular No. 3247 (25 July 1978) by R. D. Eberst also belonged to this comet. The images were also exposed at Siding Spring Observatory, using the 1.2-m UK Schmidt, on 18 and 19 July 1977. The magnitude was given as 18, while a tail extended about 3'. Although it usually reaches 17.5 mag at best, the comet was unexpectedly bright at 15.5 mag in May and June 1975. It seems to have been a temporary outburst, as the comet returned to its normal brightness in July 1977 at 18 mag. This comet is similar to 111P/Helin-Roman-Crockett; large perihelion distance, almost circular orbit, and a record of unexpected brightening in temporary outburst. Observations (VEMag = visual equivalent magnitude) Date 10x10 mag Error VEmag Coma ' 02-May-16 19.49 0.21 19.2 0.2 22-Jan-18 18.62 0.05 18.0 0.2 14-Feb-18 18.28 0.08 16.9 0.3 21-Feb-18 18.20 0.05 18.0 0.2 11-Mar-18 18.01 0.03 17.6 0.2 14-May-18 17.70 0.09 17.3 0.2 13-Sep-20 19.0 0.4