DETECTION OF EXTRASOLAR FAR-INFRARED LASERS

S.W.J. Colgan^1,2, E.F. Erickson¹,

M.R. Haas¹, D.J. Hollenbach¹,

H.A. Smith³ and V.S. Strelnitski³

¹NASA-Ames Research Center

Moffett Field, CA 94035-1000

²SETI Institute

2035 Landings Drive

Mountain View, CA 94043

³Laboratory for Astrophysics

National Air & Space Museum

Smithsonian Institution

Washington, DC 20560

Abstract

The idea of interstellar connection with the aid of lasers and the possibility of manipulating natural lasers to this end makes the search for lasing cosmic sources a part of the SETI program. Yet, apart from the very weak lasing in the 10 um CO2 band in the Martian and Venusian atmospheres, only one case of possible natural lasing, in the 4.7 um hydrogen PfBeta line from the Becklin-Neugebauer source in Orion, has been reported but never confirmed. Given hundreds of maser sources detected during the 30 years after their first discovery in 1965, the lack of detected natural lasers became a tantalizing puzzle. We undertook a search for high-gain hydrogen lasers in the far-infrared spectrum of MWC349 - a peculiar star known as a unique source of mm/submm hydrogen masers. We used the facility cryogenic grating spectrometer (CGS) on board the Kuiper Airborne Observatory. An efficient criterion of lasing is elaborated using a set of nonlasing, spontaneous emission lines as a reference. The shortest wavelength line showing the excess of radiation in our search is H10alpha at 52 um. We briefly discuss possible reasons for the lack of detectable lasers in the visual and near-infrared domains.

Even as this paper was being written, the discovery of the first natural UV laser was being reported!

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