Tuesday, 14 February 2012

The composition of Comet C/2009 P1.

Comet C/2009 P1 was discovered in August 2009 by G.J. Garradd of Siding Spring Observatory in Australia. It is a long period, Oort Cloud comet with a highly eccentric orbit tilted at 106.2° to the plain of the Solar System. At its closest to the sun in December 2011 C/2009 P1 was 1.55 AU from the sun (slightly further away than Mars), it is not clear how far the comet gets from the sun, though it is assumed to be a long way, nor how long its period (year) is.

The known orbit of C/2009 P1. From Astro Corner.

In a paper published on the online arXiv database at Cornell University Library on 1 February 2012, a team of scientists led by Lucas Paganini of the Goddard Center for Astrobiology describe the chemical composition of C/2009 P1, based upon observations of the comet by the Very Large Telescope in the Atacama Desert.

Since it was not possible to sample the comet directly, and determine the absolute quantities of compounds, the data was presented as abundances relative to the abundance of water (H₂O).


The chemical composition of comets can be used to asses where in the protoplanetary disk that formed the Solar System they originated. C/2009 P1 is rich in Carbon Monoxide, which is one of the most abundant ice molecules in inter-stellar dust clouds, but is absent in inner-system comets. It is also rich in volatile compounds that are usually absent from inner-system comets. Paganini et al. conclude from this that C/2009 P1 formed in the outer part of the original protoplanetary disk.

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