C/1907 G1 (Grigg–Mellish)

For other comets discovered by John E. Mellish, see Comet Mellish.

C/1907 G1 (Grigg–Mellish) is a long-period comet discovered independently by John Grigg and John E. Mellish in April 1907. The comet has been identified as the parent body of the delta Pavonids meteor shower.

C/1907 G1 (Grigg–Mellish)

Comet Grigg-Mellish photographed by Edward Emerson Barnard on 13 April 1907
Discovery
Discovered by	John E. Mellish John Grigg
Discovery date	8 April 1907
Designations
Alternative designations	1907b[1] 1907 II
Orbital characteristics[2]
Epoch	18 April 1907 (JD 2417683.5)
Number of observations	4
Aphelion	123.9 AU
Perihelion	0.924 AU
Semi-major axis	62.43 AU
Eccentricity	0.985205
Orbital period	~490 years
Inclination	109.95°
Longitude of ascending node	190.47°
Argument of periapsis	328.60°
Last perihelion	27 March 1907
Next perihelion	~2400
TJupiter	-0.322
Earth MOID	0.003 AU
Jupiter MOID	1.351 AU
Comet total magnitude (M1)	10.0[3]

Discovery and observations

John Grigg, in New Zealand, discovered a nebulous object near the star α Cae on 8 April 1907, however the discovery wasn't communicated quickly enough for observers in the southern hemisphere to confirm the discovery.^[4] The comet was found independently by amateur astronomer John E. Mellish, from Madison, Wisconsin, on 14 April. The comet had an apparent magnitude of 11 upon discovery.^[5] The comet was also spotted by Edward Emerson Barnard in a photographic plate exposed on 13 April while he was searching for comet C/1907 E1 (Giacobini). The comet formed a trail 13.6 arcminutes long during the one hour the plate was exposed.^[6] The comet was reported to have a coma two arcminutes across and a broad tail 8 arcminutes long on 16 April. The comet faded rapidly and it was difficult to measure with the 36-inch telescope of Lick Observatory on 7 May.^[7]

The comet was found to have a similar orbit to comet C/1742 C1,^[8] however comet Grigg–Mellish is intrinsically fainter than that comet. The comet's orbit passes very close to Earth, at a distance of 0.003 AU (0.45 million km; 0.28 million mi); Earth passes that point on 30 March. Due to the small minimum orbit intersection distance, it was suggested to be a source of meteors with a radiant point at R.A. = 20.63^h , DEC = –60.4° and a speed of Vg = 59.0 km/s.^[9]

Meteor shower

Comet Grigg–Mellish has been identified as the parent body of the delta Pavonids meteor shower. The shower has a zenithal hourly rate (ZHR) of 5 meteors per hour and peaks at March 31. An outburst was observed in 2019. The orbit of the meteors indicates that comet has an orbital period of 447 ± 80 years.^[9]