![[ Diagram of MWC 349 Disk ]](/mt/?noimg=&dark=on&url=http%3a%2f%2fccf.arc.nasa.gov%2fdx%2fbasket%2fpix%2flaserKAO.gif) | Circumstellar disk surrounding the hot star MWC 349. Maser emissions are thought tooccur in outer regions while lasers are operating nearer the central star.(CourtesyStrelnitskiet al., 1995) |
| Circumstellar disk surrounding the hot star MWC 349. Maser emissions are thought tooccur in outer regions while lasers are operating nearer the central star.(CourtesyStrelnitskiet al., 1995) |
The first "natural" laser in space was detected by scientists on boardNASA'sKuiper Airborne Observatory (KAO)as they trained the aircraft'sinfrared telescope on a young, very hot, luminous star in the constellationCygnus.
Discovery of this naturally occurring laser provides scientists with apowerful tool for probing the conditions in disks of gas and dustsurrounding young stars, according to Principal Investigator VladimirStrelnitski of theAstrophysics Laboratory,National Air and Space Museum(NASM),Washington, DC, who made the discovery. Scientistsbelieve that many of these circumstellar disks are regions where planetsare forming.
The laser is created as intense ultraviolet light from the star "pumps" orexcites the densely packed hydrogen atoms in the gaseous, dusty disksurrounding the star. Then, when the infrared light shines on the excitedhydrogen atoms, it causes the atoms to emit an intense beam of light atexactly the same wavelength, creating the circumstellar laser, accordingto Sean W. J. Colgan of the Search for Extraterrestrial Intelligence(SETI)Institute, Mountain View, CA, a co-investigator in the discovery.
The discovery was made as the KAO, the world's only flying observatory,returned toMoffett Field,CA, from observing missions based in Hawaii.Co-investigators in the discovery are Howard A. Smith, also of NASM;Michael R. Haas and Edwin F. Erickson,Ames Research Center,Mountain View, CA; and Colgan.
Strelnitski used a sensitive liquid helium-cooled spectrometer attached tothe KAO telescope to search for selected "lasing lines" in the infraredregion of the spectrum between 50-500 microns (100 to 1000 times thewavelength of visible light).
The natural laser was detected at 169 microns as the scientists viewed thenearly edge-on gas and dust disk surrounding the peculiar star known asMWC 349. The "lasing line" has an intensity six times brighter thannon-amplified spontaneous emissions at the same wavelength, Strelnitski said.
The existence of natural lasers was predicted more than 15 years ago,following the successful amplification of both microwave and visible lightwavelengths in laboratory experiments, and the discovery ofamplified microwavesin space.
(COMMENT: This statement is not exactly correct, stellar laserswere predicted more than a quarter of a century ago by the astrophysicistD.H. Menzelin a remarkable paper onLaser Action in Non-LTE Stellar Atmospheres)
American physicist and Nobel laureateCharles Townesfirst proposed thepractical amplification of electromagnetic radiation by stimulated emissionin 1951. In 1954, his group atColumbia Universitycreated the firstlaboratory amplifier of microwaves, calling it aMASER(Microwave Amplification by the Stimulated Emission of Radiation.)
In 1960Theodore Maiman atHughes Research Laboratoriesdeveloped a device to amplify visible light, creatingthe first LASER(Light Amplification by Stimulated Emission of Radiation.)
Not long after the invention of laboratory masers and lasers, the firstnatural maserswere discovered in interstellar and circumstellar gasclouds.Townes,a frequent investigator onboard the KAO, was among thediscoverers of the first strong astrophysical water masers.
Astrophysical masers,due to their extremely high intensity and spectralpurity, are valuable tools in studies of the birth and death of theirassociated stars. On Earth, many scientific and industrial applications ofmasers and lasers have been developed, such as keepingexact time,bar-code reading in supermarkets and performing"bloodless surgery."
Astrophysical masers can be observed from the ground with specialinstruments, but the major part of the infrared spectrum where potentiallasers might be seen is hidden from the ground observer by Earth'sabsorbing atmosphere.
This long awaited discovery of a natural laser was made on the lastscheduled flight of the KAO instrument -- the Ames Cryogenic GratingSpectrometer. The instrument permits sensitive detection of emission fromatoms and molecules throughout the mid- and far-infrared spectraldomain.
The KAO is scheduled for retirement this fall. NASA plans to begindevelopment of the follow-on airborne observatorySOFIAin 1996, withfirst flight scheduled for the year 2000.
Don SavageHeadquarters, Washington, DC August 29, 1995(Phone: 202/358-1547)Diane FarrarAmes Research Center, Mountain View, CA(Phone: 415/604-3934)RELEASE:95-14895-35
 | Spectral line profile of the H-26-alpha maser transition in MWC 349(Strelnitski et al., 1995)The shape of this microwave laser line (354 GHz) is similar to the H-15-alphainfrared laser line at 169 microns (1775 GHz). These velocity profiles aretypical of microwave laser emissions in many other sources and probably indicatehigh velocity outflows towards and away from the observer. |
