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NASA Hopes to Capture Cosmic Nursery

Posted on: Wednesday, 23 April 2003, 06:00 CDT

by STEPHEN STRAUSS

Last of agency's great space telescopes will map infrared light from baby stars and planets

The Globe and Mail -- All the old, cold and dirty things in the universe should soon be seen in a fresh, clean light if NASA successfully launches the last of its revolutionary space telescopes next week.

The hoped-for fallout of suddenly clearer vision will be the first pictures of baby stars and planets forming in the cosmos.

The Space Infrared Telescope Facility (Sirtf), which is roughly the size of a small car, is the last of what the U.S. National Aeronautics and Space Administration calls its four "Great Observatories" telescopes. These have included the Hubble Space Telescope, which has looked at visible light, the Compton Observatory, which has looked at gamma rays, and the Chandra X-Ray Observatory.

Sirtf's purpose is to map the infrared emissions from various parts of the universe. Invisible to our eyes, infrared light is the signature heat radiation given off by very cold (a bit above absolute zero or -273.15 C), very old (objects formed near the start of the universe) and very dusty objects.

While it is possible to monitor infrared emissions from Earth, the measurement process is fraught with intrinsic difficulties. To begin with, Earth-based telescopes generate their own heat and in the process create a measurement static called "infrared noise."

This "noise" blocks out some of the infrared light coming from space. In the case of Sirtf, the iciness of space will cool the telescope.

More importantly, many of the infrared signals are absorbed by Earth's atmosphere and therefore never make it to instruments on the planet's surface.

"In a sense, being on Earth is like living wrapped up in a blanket of atmosphere, but when you go off into space, you can unwrap the blanket and see all sorts of things you can't see from here," says James Di Francesco, an astronomer with the National Research Council in Victoria specializing in planet formation.

NASA has estimated that, depending on the Sirtf instrument being used, the telescope's readings will be hundreds to thousands of times more sensitive than any previous infrared measuring tool.

What will Sirtf, originally set to cost $2.2-billion (U.S.) but brought in at $750-million (U.S.) by a budget-conscious space agency, actually do? Take baby pictures of the stars for one thing.

Astronomers know that stars form behind billows of dust and gas that hide their birthing processes from visual telescopes -- even space-based ones like the Hubble. However, because of its long wavelength, infrared radiation pierces these clouds.

"We hope to be able to see all the constituents in the stellar nurseries, what kind of stars a particular region is making . . . and measurements of the dust clouds themselves," Dr. Di Francesco says.

Another set of baby pictures will be taken of planets. They are created when the gaseous discs that surround stars cool and then coagulate.

While Sirtf won't be able to see planets themselves, there is the hope that it will record the various stages in the process wherein the small pieces of planet-making matter -- so-called planetesimals -- come into existence.

Lastly, the telescope should begin the first census of "brown dwarfs." These are bodies too large to be planets, but too small to self-ignite into stars. While sighted only in the mid-1990s, there are theoretical reasons to believe that there are as many brown dwarfs in the universe as stars.

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