Narrowband Observations of Comets ISON (2012 S1) and 2P/Encke: Extremes of the New and the Old
Abstract
We report on narrowband filter observations of Comets ISON (2012 S1) and 2P/Encke obtained from Lowell Observatory. Observations of dynamically new Comet ISON include the first successful gas measurements of the apparition on March 5 (r = 4.57 AU) with a CN production rate of 1.3x1024 molecules/s, implying a water production rate of 1-10x1026 molecules/s for a normal range of CN-to-OH abundance ratios. Two months later the measured CN and inferred water values were about 70% higher. During the same interval the apparent dust production more than doubled, with Afρ increasing from 120 cm to 270 cm. Further observations, both photometry and imaging, are scheduled for early September and early October, and the results from these will be presented. In contrast to ISON, Comet Encke is highly evolved both thermally and physically, having made hundreds of close passages by the Sun. As a result, only a small fraction of its surface remains active and almost no micron-sized dust particles are released during outgassing. This fall's apparition will be the ninth for which we will have obtained gas production rates. The existing data imply a strong secular decrease in water production but a much smaller decrease for the minor species. These and new observations will be presented and we will examine whether or not these trends continue and the possible meaning. This research is supported by NASA's Planetary Astronomy and Planetary Atmospheres Programs.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #45
- Pub Date:
- October 2013
- Bibcode:
- 2013DPS....4540705S