6P/d'Arrest (0006P)


Type: Periodic Perihelion date: 17 September 2021 Perihelion distance (q): 1.4 Aphelion distance (Q) : 5.6 Period (years): 6.5 Eccentricity (e): 0.61 Inclination (i): 19.5 JPL orbit diagram COBS lightcurve 6P/d'Arrest was discovered in Pisces by Heinrich Ludwig d'Arrest (Leipzig, Germany) on 28 June 1851. It was described as very faint. The comet was not found on the next night because the sky was too hazy, but on 30 June, d'Arrest described it as large and faint. The 1950 return was unusual because the comet was not expected to exceed a magnitude of 12.5 (the maximum brightness of the more favorable 1943 appearance). However, about three weeks after passing closest to the sun, the comet experienced an outburst which took it to magnitude 10.5. The comet's brightest appearance to date came in 1976. A close approach to Jupiter in 1968 (0.42 AU) had decreased the perihelion distance to 1.17 AU. During the 1976 return the comet was closest to Earth on the same day it passed closest to the Sun. The result was that the comet passed only 0.15 AU from Earth on 13 August. It reached a maximum brightness of magnitude 4.9 and exhibited a tail one degree long. In 1991, A. Carusi and G. B. Valsecchi (Rome) and L. Kresak and M. Kresakova (Bratislava) independently suggested this comet was the same as a comet observed by La Hire in 1678. Independent orbits were computed by Carusi and Sitarski which confirmed the link. During 1995, the comet passed 0.3996 AU from Earth on 9 August. During the latter days of August the maximum brightness reached a magnitude of about 7.5. The comet was still magnitude 11 in early November. The comet was recovered at its 2008 apparition in late April by observers at Lowell Observatory's Anderson Mesa Station and Kachina Observatory, Flagstaff. It was around 19th magnitude. It appears to have undergone something of an outburst around the time of perihelion. Observations (VEMag = visual equivalent magnitude) Date 10x10 mag Error VEmag Coma ' 05-May-21 18.2 0.4 16-Jun-21 18.1 0.4 01-Jul-21 18.02 0.09 17.8 0.4 26-Aug-21 16.5 0.4