David Aguilar
(617) 495-7462

Christine Pulliam
(617) 495-7463


CfA Press Release


EMBARGOED FOR RELEASE: 8 am (CST) January 8, 1999

Water, Water Everywhere: New NASA Satellite Finds Stellar Nurseries to be Hot and Humid


AUSTIN, TX--With nearly flawless execution in both its launch andearly operations, the Submillimeter Wave Astronomy Satellite, or SWAS,has already produced some exciting results, including the discoverythat large amounts of water seem to saturate the interstellarmedium, while, by contrast, molecular oxygencannot be found.

Launched from a Pegasus XL vehicle on December 5, 1998, SWAS is thefirst space borne observatory to operate at submillimeter wavelenghts,a narrow band of emission lying between infrared and radio on theelectromagnetic spectrum. In only two weeks of observations, SWASseems on target for achieving its main goal: to study the molecularclouds in space, those giant star-forming regions like the one fromwhich our Sun and Solar System were born.

The news that excites astronomers most is that SWAS has found wateralmost everywhere--and molecular oxygen apparently no where.

"We have seen water in the interstellar medium before, but only in hotregions," says principal investigator Gary Melnick of theHarvard-Smithsonian Center for Astrophysics. "SWAS, on the otherhand, has found water in much cooler regions, and that's importantbecause most of the interstellar medium is cold and that may mean thatwater is in a lot more places than we knew."

Equally exciting and revealing, SWAS has sofar seen no molecular oxygen in the interstellar clouds it has observed. In just two weeks of science observations, SWAS has set the most stringent limits to date on the amount of molecular oxygen in star-forming clouds. The apparent absence ofoxygen may actually help astronomers pinpoint the age of thosemolecular clouds.

"Molecular clouds are like chemical laboratories," says Melnick. "Ourtheories tell us oxygen won't appear until the cloud reaches a certainage. SWAS, in its future observations, will help us test thosetheories and determine more about these star factories."

Melnick and his colleagues are also looking forward to using SWAS tocreate large-scale maps of different molecules in space. Unlikewater and oxygen, astronomers already know that carbon molecules,including carnon monoxide, are abundant in the galaxy. SWAS will beable to make maps of warm molecules across vast swaths of the sky -something that is nearly impossible from ground-based facilities.

With its ability to conduct pointed, high-spectral- resolutionobservations of molecular clouds that are either sites of ongoing orfuture star formation, SWAS may also be able to answer some basicquestions: 1) Where is the oxygen hiding?; 2) How do collapsingclouds cool so they can form as stars and planets?; and, 3) What isthe internal structure of the clouds?

In addition to the Harvard-Smithsonian Center for Astrophysics, theSWAS project also includes contributors from the University ofMassachusetts at Amherst, Cornell University, Johns HopkinsUniversity, NASA Ames, and the University of Cologne in Germany.

For more information, contact:

Gary Melnick, 617/495-7388, gmelnick@cfa.harvard.edu

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