An outburst of delta Pavonids and the orbit of parent comet C/1907 G1 (Grigg-Mellish)

Abstract

The CAMS New Zealand meteor shower survey detected a brief outburst of delta Pavonids (IAU shower 120, code DPA) with a compact radiant on March 31, 2019. This is the first instrumental detection of a shower long suspected to exist by visual observers monitoring the theoretical radiant of parent comet C/1907 G1 (Grigg-Mellish), despite it being listed in comet catalogs only with a parabolic orbit. The 2019 detection of an associated meteor shower confirms that this comet moves in an elliptical orbit. The range of allowed orbit solutions fitted to the 1907 observations of the comet strongly correlate node and semi-major axis. Taking into account the difference in node between comet orbit and dust trail, the time of the outburst constrains the comet orbital period to 447 ​± ​80 years (heliocentric), having last been near the sun in A. D. 1460 ​± ​80 years. The corresponding elliptical orbital elements for C/1907 G1 are presented. The short 23-min duration of the outburst (FWHM ​= ​16 ​min) confirms that C/1907 G1 is a small comet, having ejected dust with low ejection speeds. It passed close enough to Earth orbit to be a potentially hazardous comet in future returns.