Comets - 143P Kowal-Mrkos - 0143P
Type Periodic Perihelion Date 7 May 2018 Perihelion Distance (q) 2.5 Aphelion Distance (Q) 6.1 Period (Years)   8.9 Eccentricity (e)   0.41 Inclination (i)   4.7 Click for NASA orbit diagram
Hills Observatory: 1 January 2013 to 6 May 2018
During September of 1984, C. T. Kowal (Palomar Observatory, California, USA) was examining photographic plates exposed earlier in the year with the 1.2-m Schmidt telescope, when he found the unmistakable trail of a comet. The trail appeared on images exposed on 23 and 30 April 1984.  Kowal estimated the magnitude as 15 and described the comet as "almost stellar, with a faint but definite coma." B. G. Marsden quickly realized the Kowal's object was identical to a minor planet found by A. Mrkos (Klet Observatory, Czech Republic) on a photographic plate exposed on 2 May. Mrkos had noted that the minor planet (designated 1984 JD) was stellar on the first image, but slightly diffuse on the second. The magnitude was given as 16.0. During March of 2000, the Lincoln Laboratory Near-Earth Asteroid Research (LINEAR) project provided observations of an asteroidal object from 9 and 13 March, which was subsequently designated 2000 ET90. Following additional observations by LINEAR on 4 and 8 April, G. V. Williams (Central Bureau for Astronomical Telegrams) noted the apparently cometary orbit and requested further observations. Prediscovery images were subsequently reported by LINEAR for 7 February (magnitude 19.2-19.7), and by the Catalina Sky Survey for 1 March (magnitude 17.2-17.4). Another observation was subsequently found by the Lowell Observatory Near-Earth Object Search (LONEOS) program for 2 April (magnitude 16.9). From the subsequent orbit spanning nearly two months, Marsden suspected this was comet Kowal-Mrkos and an independent suggestion was also made by C. W. Hergenrother. Marsden quickly confirmed that 2000 ET90 was identical to Kowal-Mrkos. He also noted that the prediction for the 2000 return was 125 days too late. Date 10x10 mag Error Kphot mag Coma ' 26-Dec-17 18.31 0.13 18.0 0.2 21-Jan-18 18.20 0.06 18.1 0.2 14-Feb-18 17.89 0.01 17.8 0.2 21-Feb-18 17.75 0.03 17.5 0.2 11-Mar-18 17.32 0.06 17.2 0.2 20-Mar-18 17.24 0.02 16.9 0.2 08-Apr-18 16.57 0.01 16.0 0.3 21-Apr-18 16.86 0.05 16.5 0.2