The scattering phase function of comet 67P/Churyumov–Gerasimenko coma as seen from the Rosetta/OSIRIS instrument

Bertini, I.; La Forgia, F.; Tubiana, C.; Güttler, C.; Fulle, M.; Moreno, F.; Frattin, E.; Kovacs, G.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A’Hearn, M. F.; Barucci, M. A.; Bertaux, J-L.; ... (2017). The scattering phase function of comet 67P/Churyumov–Gerasimenko coma as seen from the Rosetta/OSIRIS instrument. Monthly notices of the Royal Astronomical Society, 469(Suppl_2), S404-S415. Oxford University Press 10.1093/mnras/stx1850

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The study of dust, the most abundant material in cometary nuclei, is pivotal in understanding the original materials forming the Solar system. Measuring the coma phase function provides a tool to investigate the nature of cometary dust. Rosetta/OSIRIS sampled the coma phase function of comet 67P/Churyumov–Gerasimenko, covering a large phase angle range in a small amount of time. Twelve series were acquired in the period from 2015 March to 2016 February for this scientific purpose. These data allowed, after stray light removal, measuring the phase function shape, its reddening, and phase reddening while varying heliocentric and nucleocentric distances. Despite small dissimilarities within different series, we found a constant overall shape. The reflectance has a u-shape with minimum at intermediate phase angles, reaching similar values at the smallest and largest phase angle sampled. The comparison with cometary phase functions in literature indicates OSIRIS curves being consistent with the ones found in many other single comets. The dust has a negligible phase reddening at α < 90°, indicating a coma dominated by single scattering. We measured a reddening of [11–14] %/100 nm between 376 and 744 nm. No trend with heliocentric or nucleocentric distance was found, indicating the coma doesn’t change its spectrum with time. These results are consistent with single coma grains and close-nucleus coma photometric results. Comparison with nucleus photometry indicates a different backscattering phase function shape and similar reddening values only at α < 30°. At larger phase angles, the nucleus becomes significantly redder than the coma.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Thomas, Nicolas

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering

ISSN:

0035-8711

Publisher:

Oxford University Press

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

06 Apr 2018 15:43

Last Modified:

06 Apr 2018 15:43

Publisher DOI:

10.1093/mnras/stx1850

BORIS DOI:

10.7892/boris.107576

URI:

https://boris.unibe.ch/id/eprint/107576

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