Radio OH observations of 9P/Tempel 1 before and after Deep Impact

Ellen S. Howell, Amy J. Lovell, Bryan Butler, F. Peter Schloerb

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We observed 18-cm OH emission in Comet 9P/Tempel 1 before and after Deep Impact. Observations using the Arecibo Observatory 305 m telescope took place between 8 April and 9 June, 2005, followed by post-impact observations using the National Radio Astronomy Observatory 100 m Green Bank Telescope 4-12 July, 2005. The resulting spectra were analyzed with a kinematic Monte Carlo model which allows estimation of the OH production rate, neutral gas outflow velocity, and distribution of the out-gassing from the nucleus. We detected typically 24% variability from the overall OH production rate trend in the two months leading up to the impact, and no dramatic increase in OH production in the days post-impact. Generally, the coma is well-described, within uncertainties, by a symmetric model with OH production rates from 1.6 to 7.4 × 1027   mol s-1, and mean water outflow velocity of 0.75 ± 0.03   km s-1. At these low production rates, collisional quenching is expected to occur only within 20,000 km of the nucleus. However, our best-fit average quenching radius is 64,200 ± 22,000 km in April and May.

Original languageEnglish (US)
Pages (from-to)469-480
Number of pages12
Issue number2 SUPPL.
StatePublished - 2007
Externally publishedYes


  • coma
  • Comet Tempel-1
  • Comets
  • Radio observations
  • Spectroscopy

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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