Issue |
A&A
Volume 442, Number 3, November II 2005
|
|
---|---|---|
Page(s) | 1107 - 1120 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20041571 | |
Published online | 14 October 2005 |
The chemistry of C2 and C3 in the coma of Comet C/1995 O1 (Hale-Bopp) at heliocentric distances rh ≥ 2.9 AU
1
Institute of Planetary Research, DLR, Rutherfordstr. 2, 12489 Berlin, Germany e-mail: joern.helbert@dlr.de
2
Institute of Planetary Exploration, DLR, Rutherfordstr. 2, 12489 Berlin, Germany
3
Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510, USA
Received:
1
July
2004
Accepted:
21
April
2005
The extraordinary activity of comet C/1995 O1 (Hale-Bopp) made it possible to observe the emission bands of the radicals and
in the optical wavelengths range at heliocentric distances larger than 3 AU. Based on these observations, we perform an analysis of the formation of
and
in a comet coma at large heliocentric
distances. We present the most complete chemical reaction network used until today, computing the formation of C2 and C3 from C2H2, C2H6, and C3H4 as their parent molecules. The required photodissociation rates of
and
had to be derived based on the observations. The spatial distributions of
and
calculated with the chemical model show good agreement with the observations over the whole range of heliocentric distances covered in this work. Based on the production rates for C2H2, C2H6, and C3H4, abundance ratios are obtained for heliocentric distances
AU. In comet Hale-Bopp, C2H2 and C2H6 were measured directly by infrared observations only at heliocentric distance
AU (Dello Russo et al. 2001). The model presented here greatly extends the heliocentric distance range over which hydrocarbons can be studied in the coma of comet Hale-Bopp. We discuss possible indications of these abundance ratios for the formation region of comet Hale-Bopp.
Key words: comets: general / comets: individual: C/1995 O1 (Hale-Bopp) / planets and satellites: formation / interplanetary medium
© ESO, 2005
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