UW is key partner in push to build monster telescope

August 02, 2000

The University of Wisconsin-Madison has joined forces with an international consortium to help build and operate a major new South African observatory.

UW-Madison's bid to gain access to what will become one of the world's largest optical telescopes will help maintain the stature of its world-renowned program in astronomy,

The planned observatory, known as SALT for South African Large Telescope, will boast a 10- by 11-meter (32-by-36 foot) hexagonal segmented mirror that will make the telescope the largest in the southern hemisphere and comparable in size and power to the world's largest telescopes.

The new observatory groundbreaking is scheduled for Friday, Sept. 1, and the telescope should see "first light" sometime in 2004. The observatory will permit scientists to peer deep into the universe, observe as many as 100 objects at a time and gather critical new insights into the menagerie of objects that populate the cosmos.

"In certain ways, this telescope will have unique and superior capabilities" to the growing number of mega-telescopes cropping up on mountaintops worldwide, says Matthew Bershady, a UW-Madison professor of astronomy and a leader of the team of UW-Madison astronomers involved in the development of the massive telescope.

The new telescope will permit UW-Madison astronomers and their students to conduct a versatile research program, including studies of how matter assembled into galaxies after the Big Bang, the nature and chemistry of interstellar and intergalactic matter, and star and stellar system formation.

Phillip Certain, dean of the UW-Madison College of Letters and Science, says the telescope will play a critical role in keeping UW-Madison at the apex of an extremely competitive business. Its role in research and education, including undergraduate education, can't be overemphasized, he says.

The SALT Observatory is planned for a desert mountaintop near Sutherland, South Africa, about 350 kilometers (217 miles) northeast of Cape Town at the southern tip of Africa.

The SALT consortium includes institutions from South Africa, Germany, Poland, New Zealand and the United States. UW-Madison, which has pledged a minimum of $4.8 million toward constructing, equipping and operating the observatory, becomes the second biggest stakeholder in the consortium after the South African government.

The total cost of the observatory - telescope, buildings, instrumentation and operation for 10 years - is roughly $35 million, according to Kenneth H. Nordsieck, a UW-Madison professor of astronomy.

As a partner in the SALT Observatory, UW-Madison would gain a percentage of observing time in proportion to its contribution to the project. Currently, UW-Madison is a major partner in the WIYN Telescope consortium, a 3.5-meter (11.5-foot) telescope located atop Kitt Peak, Ariz., and has its own observatory with two smaller telescopes at Pine Bluff, Wis.

A key contribution to be made by UW-Madison to the new telescope will be a novel imaging spectropolarimeter, one of three instruments to which the light from distant stars, galaxies and planets will be routed. The other two planned instruments are an imaging camera and a multi-object high-resolution spectrograph, a device that can sample light from many objects at once and which breaks light down into its constituent, telltale wavelengths for study.

The spectropolarimeter will cost an estimated $1.9 million. The device will be at the heart of the new observatory and will help give SALT a performance edge that will put the data it collects on a plane with observations made by much costlier telescopes.

"This is a chance to build the best spectropolarimeter in the world," says Nordsieck, an astronomer with long experience building astronomical instruments to be deployed in space."It's a device that will make the SALT Telescope more efficient and versatile."

The Wisconsin spectropolarimeter, in fact, will be built using the same philosophy that guides the making of space-based instruments. Typically, telescope instruments are housed in ancillary buildings or in areas away from the primary mirror, but because this device will be positioned on a truss directly above the telescope's primary mirror, the spectropolarimeter will need to be compact and light. When completed, the device will be about the size of a kitchen stove.

The South African mountaintop location gives access to the southern sky and objects of intense interest to astronomers, including the plane of the Milky Way and the Magellanic Clouds, the two galaxies nearest our own.

The SALT Telescope is closely modeled on the Hobby-Eberly Telescope in west Texas. At the heart of the telescope will be a primary mirror composed of 91 identical 1-meter hexagonal mirror segments.Mounted on a common structure, the segments will bring the light they collect to a common focus.

Weighing 13 tons and with a length of 13 meters (about 43 feet), the telescope will cost only 20 percentof the cost of a conventional 10-meter (32-foot) telescope because the mirror will be fixed at a constant angle from the horizon. Observations of stars and other objects are made by a combination of rotating the telescope on a turntable, the rotation of the Earth on its axis, and the manipulation of instruments at the telescope's point of focus.

"For a big telescope of this kind, the field of view for the instruments is exceptionally large," says Bershady. "That means you can do a lot of things at once for very little cost."

For example, measurements of all the stars in globular clusters, which are tightly packed groupings of thousands of stars, can be made with extraordinary efficiency. And object-rich regions of the sky such as the plane of the Milky Way can be quickly and systematically surveyed.

UW-Madison's participation in the SALT consortium will help the university's astronomy department remain a leader in astronomy research and education, according to Nordsieck.

"Access to state-of-the-art laboratory facilities is crucial to participating in the forefront of research," he says. "In astronomy, that means access to the new generation of large-aperture optical telescopes like SALT. It will be a cornerstone of our research program for the next 15 years."
More information on the SALT Observatory and Telescope can be found online at: http://www.salt.ac.za.

NOTE TO PHOTO EDITORS: High-resolution images and a rendering of the planned SALT Observatory can be obtained by visiting: http://www.news.wisc.edu/newsphotos/salt.html

Terry Devitt 608-262-8282, trdevitt@facstaff.wisc.edu

University of Wisconsin-Madison

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