Southern African Large Telescope makes its debut

09/01/05

Rutgers contributes instrument package to examine building blocks of universe



The Lagoon Nebula is a region about 3,800 light years away in which stars of high mass and luminosity are being born, emitting enough ultraviolet radiation to stimulate atoms in the surrounding gas clouds to emit light. The light-gathering capability of SALT will allow astronomers to study motions in the gas clouds, perhaps leading them to revise ideas of how stars are born.
Click here for a high resolution photograph.

NEW BRUNSWICK/PISCATAWAY, N.J. – Rutgers, The State University of New Jersey, today joined 10 partners worldwide to release the first full-color astronomical images made by the Southern African Large Telescope (SALT) in South Africa. This milestone – known as "first light" in astronomical circles – marks the debut of scientific observations on the southern hemisphere's largest telescope.

The new images provide views of newly born stars amid brilliantly glowing gas clouds, clusters of stars more than twice the age of our own sun, and another galaxy similar to our own Milky Way. Gathering more than 25 times as much light as any existing African telescope, SALT can detect objects as faint as a candle flame on the moon.

"For the first time, astronomers can now have a detailed 24-hour view of the southern night sky by combining South African observations with similar images from telescopes in Australia and Chile," said Theodore Williams, professor of physics and astronomy at Rutgers. "This is essential for studying objects that change rapidly, such as supernovae and time-variable stars."

SALT is located on the grounds of the South African Astronomical Observatory near Sutherland, about 220 miles inland from Cape Town. It joins six other smaller telescopes at the site. The telescope has been built over the past five years – a rapid schedule for a big telescope project – and costs have been kept within the original $20 million budget.

Rutgers holds a 10 percent partnership in SALT, having contributed $2.4 million toward construction. The university has committed an additional $1 million for operations during the first 10 years. In 1999, Rutgers became the first institutional partner to join the National Research Foundation of South Africa in the SALT project.

Rutgers and the University of Wisconsin-Madison, another SALT partner, are deploying an advanced instrument package on the telescope that will give astronomers new insights into the building blocks of the universe – from dust clouds to star clusters to distant galaxies. The instrument, known as the Prime Focus Imaging Spectrograph, or PFIS, will break down light into colors, or wavelengths, to examine such properties as the temperatures and chemical compositions of stars as well as how fast they are moving. The spectrograph also will capture and analyze polarized light, which can reveal the nature of cosmic dust and magnetic fields around black holes, quasars and galactic nuclei.

The Wisconsin/Rutgers PFIS, to be named the Robert Stobie Spectrograph in honor of the SALT board's late chair, is slated for installation in mid-September. Astronomers from both universities expect to begin collecting data in early October. Unlike traditional spectrographs, which gather light from a tiny point or a narrow slit, Rutgers astronomers designed a way to collect images across the broad two-dimensional field of the telescope.

"This will speed our study of globular star clusters, which are the oldest identifiable objects in our galaxy and contain clues about how galaxies form," said Carlton Pryor, Rutgers physics and astronomy professor. "With traditional instruments, we see one star at a time. With PFIS, we'll capture data on a thousand stars simultaneously."

Rutgers also contributed a key structural element for PFIS – a six-foot-wide metal truss on which the spectrograph will be mounted 10 stories above the telescope's 36-foot-wide (11 meter) mirror array. Rutgers instrument makers meticulously assembled the truss from an exotic metal alloy that maintains its shape to one-thousandth of an inch under the wide temperature swings of South Africa's high plains – essential to ensure sharp images during long exposures.

SALT's design involves rotating the telescope at its base to select a portion of sky for observation, then moving instruments at the top of the telescope to precisely track specific objects. The design, which can access nearly three-quarters of the visible sky, is based on the Hobby-Eberly Telescope at the MacDonald Observatory in Texas.

"This gives astronomers incredible bang-for-the-buck," Williams said. "We're able to capture as much light as a fully steerable telescope of similar size, at one-fifth the cost, putting leading-edge observations within reach of more investigators."

Source: Eurekalert & others

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