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Astron. Astrophys. 325, L5-L8

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Letter to the Editor

Radio detection of ammonia in comet Hale-Bopp

M.K. Bird1, W.K. Huchtmeier2, P. Gensheimer2, T.L. Wilson2, P. Janardhan*1, and C. Lemme3

1Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany
2Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
3Institut für Planetenerkundung, DLR, Rudower Chaussee 5, D-12489 Berlin, Germany

Received 17 June 1997 / Accepted 26 June 1997


Radio emission from ammonia, a suspected parent molecule in comets, was detected from comet Hale-Bopp near its perihelion passage with the 100-m Effelsberg Radio Telescope. Signals from the five lowest metastable inversion transitions of NH3 were obtained to derive a rotational temperature of 104 FORMULA 30 K, assumed to be representative of the kinetic temperature in the comet's inner coma (R < 5000 km). The ammonia production rate at perihelion is calculated from these observations to be 6.6 FORMULA 1.3 FORMULA 1028 s-1 (almost two tons of ammonia per second). Compared with independently determined water production rates near perihelion, the implied ammonia abundance ratio to water is in the range 1.0-1.8%.

Key words: radio line emission - comets - comet Hale-Bopp

*Permanent address: Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, India

Send offprint requests to: M.K. Bird

© European Southern Observatory (ESO) 1997