C/2009 P1 (Garradd)

For other comets of the same name, see Comet Garradd.

Comet Garradd, formal designation C/2009 P1, is a non-periodic comet that was observed between September 2008 and March 2013.^[6] It is one of 17 comets discovered by Australian astronomer, Gordon J. Garradd.

C/2009 P1 (Garradd)

Comet C/2009 P1 (Garradd) imaged from Italy on 23 September 2011
Discovery[1]
Discovered by	Gordon J. Garradd
Discovery site	Siding Spring Observatory
Discovery date	10 August 2009
Orbital characteristics[2][3]
Epoch	22 November 2011 (JD 2455887.5)
Observation arc	5.42 years
Earliest precovery date	27 September 2008
Number of observations	9,044
Aphelion	~4,770 AU (inbound) ~12,000 AU (outbound)
Perihelion	1.551 AU
Eccentricity	0.99935 (inbound) 0.99974 (outbound)
Orbital period	~116,000 years (inbound) ~462,000 years (outbound)
Inclination	106.18°
Longitude of ascending node	325.99°
Argument of periapsis	90.747°
Mean anomaly	–0.0005°
Last perihelion	23 December 2011
TJupiter	–0.432
Earth MOID	1.253 AU
Jupiter MOID	1.307 AU
Physical characteristics[4][5]
Dimensions	3.2–6.8 km (2.0–4.2 mi)
Mean diameter	5.0 km (3.1 mi)
Synodic rotation period	11.0±0.8 hours
Comet total magnitude (M1)	8.8
Apparent magnitude	5.8 (2012 apparition)[6]

Physical characteristics

Ultraviolet observations from the Swift Observatory revealed that the comet lost about 4.0×10¹¹ kg of ice and dust during its most recent apparition.^[7] It was previously described as having one of the highest dust-to-gas ratios ever observed from a comet since Hale–Bopp in 1997.^[8][9]

Optical spectrometer observations conducted at SAO revealed molecular emissions of organic chemicals, particularly diatomic carbon (C
₂) and tricarbon (C
₃), cyanogens (CN and CN
₂), hydrocarbons (CH and CH+), and carbon monoxide (CO+), within the comet's coma,^[10] where the gas production rate of C
₂ and C
₃ atoms were measured at 4.84×10²⁶ and 2.16×10²⁵ mol/sec, respectively.^[11]

The nucleus of C/2009 P1 (Garradd) is estimated to have an effective diameter of 5.0 km (3.1 mi),^[4] rotating once around its axis every 11.0±0.8 hours.^[5]