By Terry Devitt, trdevitt@facstaff.wisc.edu
 

Astronomers from UW-Madison and several collaborating institutions have won a major contract with NASA to perform a detailed survey of the inner regions of the Milky Way using the Space Infrared Telescope Facility, a telescope that will be boosted into orbit around the sun in 2002.
 
"This is the last of NASA’s ‘great observatories,’" says Edward Churchwell, a UW-Madison astronomer. Major orbiting observatories developed by NASA include the Hubble Space Telescope, the Chandra X-ray Telescope and the Compton Gamma Ray Observatory. Churchwell will lead a collaboration of astronomers from half a dozen institutions to sample infrared starlight from the inner reaches of our galaxy using the $600 million satellite.
 
"Our proposal is to map the inner two-thirds of the galaxy," Churchwell says. The region is rich in young stars and star clusters, luminous nebulae, brown dwarfs and substellar objects, but it can only be sampled by infrared and radio telescopes, Churchwell explains.
 
"This is the richest part of our galaxy and we’ll see things there that we’ve never seen before," Churchwell predicts.
 
As its name implies, the Space Infrared Telescope Facility is designed to sample light in the infrared region of the electromagnetic spectrum. Infrared light, invisible to the unaided eye, is given off by stars, planets, nebulae and many other objects that populate the cosmos.
 
By looking at stars and other objects in the infrared, astronomers gain insight into how stars are formed, the distribution of stars in the inner Milky Way and the population of substellar objects — dark, planet-sized objects — that reside there.
 
Perhaps more importantly, astronomers use infrared light to peel back obscuring clouds of gas and dust that hide many objects from view. For example, scientists know that in the inner regions of our galaxy there are great stellar nurseries where new stars are born and concentrated, but those nurseries are completely hidden by an obscuring veil of dust and gas, a veil that can be parted by the Space Infrared Telescope Facility.
 
"We’re going to learn a lot about the stellar content of our galaxy," Churchwell says. "The inner region of the galaxy is completely opaque, except in radio and the infrared. But radio can’t detect normal stars, where as in the infrared the obscuring dust can be penetrated, and I’m dead sure we’ll see a lot of new things."
 
The orbiting telescope will have three scientific instruments on board when it is launched into solar orbit in mid-2002. Churchwell’s team will use an Infrared Array Camera to capture detailed pictures of stars, star clusters and other objects currently hidden in the inner regions of the galaxy.
 
Using the camera, Churchwell says, it may even be possible to look through the opaque plane of our galaxy to discover new galaxies and many other objects in what are now completely unexplored regions of space.
 
The observing program to be led by Churchwell and his colleagues is known as a "legacy program" because it will use the telescope for long periods of time to catalog the stars and other objects in wide swaths of the inner galaxy. The data will then be made available to other astronomers via the World Wide Web.
 
In the first year of science operations, the team will be granted 400 hours of observing time to catalog the stellar wealth of the inner galaxy. Those data sets, made available to the broad community of astronomers, will help answer fundamental questions such as how
stars are formed and what kinds of stars occur where and with what frequency in the galaxy.
 
"We’re going to be looking at where most of the mass in our galaxy is situated. This is where a lot of the action is in terms of star formation," says Churchwell, "and our surveys will help us figure out the content of our galaxy."
 
IMAGE CAPTION:
[http://www.news.wisc.edu/news/images/SIRTF_Orbit00.jpg]
In this artist’s rendition, the Space Infrared Telescope Facility (SIRTF) is seen in its Earth-trailing orbit around the Sun. This innovative orbit produces many advantages, from a more benign thermal environment for the super-cooled detectors, to a better view of the open sky, away from the Earth and the Moon. (Photo: courtesy Jet Propulsion Laboratory)