Spatially Resolved Spectroscopic Observations of Na and K in the Tail of Comet C/2011 L4 (PanSTARRS)
Abstract
We used the Dunn Solar Telescope (DST) of The National Solar Observatory to obtain spectroscopic observations of comet C/2011 L4 (PanSTARRS) on 13 and 14 March 2013. The DST has the advantage for comet observations that one can observe the comet when it is close to the Sun. At the time of our observations, comet PanSTARRS was at 0.31 and 0.32 AU heliocentric distance. We used the Horizontal Spectrograph to observe five different spectral regions of the coma. The resolving power was 50,000 - 60,000. The slit was 0.3 arcsec wide and 171 arcsec long. At the comet's geocentric distance, the slit covered 1.43e5 km. The comet was approximately centered on the slit. We observed strong emissions from sodium (D1@589.592nm and D2@588.995nm) and potassium (D1@770.108nm and D2@671.701nm), along with a weak continuum. Lithium was not detected. The sodium was visible on the optocenter and the tailward side of the comet and extended to the edge of the slit (i.e. at least 70,000km tailward). It shifted redward at larger cometocentric distances, attributable to the acceleration of sodium by solar radiation pressure. The potassium was much weaker than the sodium and does not appear to extend as far from the optocenter. In this paper, we will show the distribution of these gases and compare their relative strengths. We will discuss the effects of the different photodissociative lifetimes of sodium and potassium and how they dictate what we observed.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #45
- Pub Date:
- October 2013
- Bibcode:
- 2013DPS....4550205C