Photometry of the Oort Cloud comet C/2009 P1 (Garradd): Pre-perihelion observations at 5.7 and 2.5 AU. (1st November 2016)

• Record Type: Journal Article
• Authors: Mazzotta Epifani, E.; Snodgrass, C.; Perna, D.; Dall'Ora, M.; Palumbo, P.; Della Corte, V.; Alvarez-Candal, A.; Melita, M.; Rotundi, A.
• Is Part Of: Planetary and space science. Volume 132(2016)
• Page Start: 23
• Page End: 31
• Publication Date: 2016-11-01
• Subjects: Comets -- Dust -- Comets -- Coma; Space sciences -- Periodicals; Atmosphere, Upper -- Periodicals; Sciences spatiales -- Périodiques; Haute atmosphère -- Périodiques; 523
• DOI: 10.1016/j.pss.2016.07.007
• Languages: English
• ISSNs: 0032-0633

Abstract

Abstract: The aim of this paper is to contribute to the characterization of the general properties of the Long Period Comets (LPCs) family, and in particular to report on the dust environment of comet C/2009 P1 (Garradd). The comet was observed at two epochs pre-perihelion, at ~6 AU and at ~2.5 AU: broad-band images have been used to investigate its coma morphology and properties and to model the dust production rate. Comet C/2009 P1 (Garradd) is one of the most active and "dust producing" LPCs ever observed, even at the large heliocentric distance r h ~6 AU. Its coma presents a complex morphology, with subtle structures underlying the classical fan-shaped tail, and, at r h ~2.5 AU, also jet-like structures and spiralling outflows. In the reference aperture of radius ρ =5°×10 4 km, the R-A f ρ is 3693±156 cm and 6368±412 cm, in August 2010 ( r h ~6 AU) and July 2011 ( r h ~2.5 AU), respectively. The application of a first order photometric model, under realistic assumptions on grain geometric albedo, power-law dust size distribution, phase darkening function and grain dust outflow velocity, yielded a measure of the dust production rate for the two epochs of observation of Q d =7.27×10 2 kg/s and Q d =1.37×10 3 kg/s, respectively, for a reference outflow dust velocity of v small =25 m/s for small (0.1–10 µm) grains and v large =1 m/s for large (10 µm–1 cm) grains. These results suggest that comet Garradd is one of the most active minor bodies observed in recent years, highly contributing to the continuous replenishment of the Interplanetary Dust Complex also in the outer Solar System, and pose important constraints on the mechanism(s) driving the cometary activity at large heliocentric distances. Highlights: Very active and "dusty" comet, even at r h ~6 AU. Complex coma morphology, with jet-like structures and spiralling outflows. Measured dust loss rate Q d among the highest for minor bodies at small r h (<3 AU).