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Title:
Activity of comets at large heliocentric distances pre-perihelion
Authors:
Meech, K. J.; Pittichová, J.; Bar-Nun, A.; Notesco, G.; Laufer, D.; Hainaut, O. R.; Lowry, S. C.; Yeomans, D. K.; Pitts, M.
Affiliation:
AA(Univ. Hawai'i, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA), AB(Univ. Hawai'i, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; Astronomical Institute of Slovak Academy of Sciences, Dúbravská cesta 9, 845 04 Bratislava, Slovak Republic.), AC(Tel Aviv University, Dept. of Geophysics and Planetary Sciences, Tel Aviv 69978, Israel), AD(Tel Aviv University, Dept. of Geophysics and Planetary Sciences, Tel Aviv 69978, Israel), AE(Tel Aviv University, Dept. of Geophysics and Planetary Sciences, Tel Aviv 69978, Israel), AF(European Southern Observatory, Casilla 19001, Santiago 19, Chile), AG(Jet Propulsion Lab, MS 183-301, 4800 Oak Grove Drive, Pasadena, CA 91109, USA), AH(Jet Propulsion Laboratory, MS 301-150, Pasadena, CA 91109-8099, USA), AI(Univ. Hawai'i, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA)
Publication:
Icarus, Volume 201, Issue 2, p. 719-739. (Icarus Homepage)
Publication Date:
06/2009
Origin:
ELSEVIER
DOI:
10.1016/j.icarus.2008.12.045
Bibliographic Code:
2009Icar..201..719M

Abstract

We present observational data for two long-period and three dynamically new comets observed at heliocentric distances between 5.8 to 14.0 AU. All of the comets exhibited activity beyond the distance at which water ice sublimation can be significant. We have conducted experiments on gas-laden amorphous ice samples and show that considerable gas emission occurs when the ice is heated below the temperature of the amorphous-crystalline ice phase transition (T˜137 K). We propose that annealing of amorphous water ice is the driver of activity in comets as they first enter the inner Solar System. Experimental data show that large grains can be ejected at low velocity during annealing and that the rate of brightening of the comet should decrease as the heliocentric distance decreases. These results are consistent with both historical observations of distant comet activity and with the data presented here. If observations of the onset of activity in a dynamically new comet are ever made, the distance at which this occurs would be a sensitive indicator of the temperature at which the comet had formed or represents the maximum temperature that it has experienced. New surveys such as Pan STARRS, may be able to detect these comets while they are still inactive.
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