103P/Hartley (0103P)

Type: Periodic Perihelion date: 12 October 2023 Perihelion distance (q): 1.1 Aphelion distance (Q) : 5.9 Period (years): 6.5 Eccentricity (e): 0.69 Inclination (i): 13.6 JPL orbit diagram COBS lightcurve Periodic comet 103P/Hartley 2 is classed as a young, dwarf comet, with a nucleus roughly 2.2 km in diameter that rotates once every 18.1 hours. It belongs to the Jupiter family of comets (comets with periods less than 20 years). The discovery plate was exposed on 15 March 1986 and, after it was developed, Malcolm Hartley (U. K. Schmidt Telescope Unit, Siding Spring Observatory, New South Wales, Australia) noted the diffuse trail of a comet. He estimated the magnitude as 17-18 and added that a faint tail was evident. Further photographic plates were exposed on 17 and 20 March, whereupon Hartley annnounced his discovery to the Central Bureau for Astronomical Telegrams. During the early decades of the 20th century, the orbital period had been 9.3 years. A close approach to Jupiter in August 1947 (0.22 AU) reduced the period to 7.9 years, while another close approach during April 1971 (0.09 AU) reduced the period to 6.1 years. The comet has been seen at every return since its discovery. The 2010 return was exceptional, as the comet passed 0.12 AU from Earth on 20 October, and the Deep Impact space craft passed about 1,000 kilometers from the comet on 4 November. Observations (VEMag = visual equivalent magnitude) Date 10x10 mag Error VEmag Coma ' 15-Jun-23 18.6 0.4 19-Jun-23 18.3 0.4 17-Aug-23 11.7 5.1