2005ApJ...620..487J

The outflows from comets in orbit around G-type main-sequence stars can be detected when they produce transient OH absorption lines in the spectrum near 3100 Å of the host star. There is only about a 3x10^–8 probability of detecting an analog to comet Hale-Bopp orbiting an analog to the Sun. However, for young solar-type stars with very large numbers of comets, possibly delivering water to terrestrial planets, there is as much as a 1% chance that any sufficiently sensitive, randomly timed observation may detect such transient absorption.