Contact: Robert Irion (408/459-2495)
KECK TELESCOPE MEETS MOST EXPECTATIONS, SAYS PROJECT SCIENTIST
Fine-tuning Keck I, completing Keck II, and developing adaptive optics keeps observatory humming
* This release is embargoed until 12:30 p.m. EDT Tuesday, June 13, when Jerry Nelson will speak at a press conference on the Keck Telescope at the American Astronomical Society meeting.
Nelson also will deliver the 1995 Heineman Prize Lecture, "The Keck Observatory: Challenges and Promise," at 11:40 a.m. EDT Thursday, June 15, in the Allegheny I and II rooms, Pittsburgh Vista Hotel.
PITTSBURGH, PA--The W. M. Keck Telescope, mankind's compound eye on the sky, is working smoothly and has yielded unparalleled results in its first 19 months of regular scientific observations, says the astronomer who conceived the telescope two decades ago.
Any lingering doubts about the viability of Keck's segmented- mirror design have dissolved with the unveiling of new regions of the cosmos, many of them inaccessible to smaller telescopes. Technicians are still striving to improve the quality of the telescope's images, which are "superb" but have not quite reached an optimal level, says project scientist Jerry Nelson.
At the same time, observatory teams are finishing the telescope's twin, Keck II, which should take a "first light" image in November 1995. Progress is also being made on an advanced adaptive-optics system for Keck II, using a low-power laser guide star invisible to the human eye. Nelson expects that system to be ready for testing by 1997.
"We are doing science at Keck I on 85 to 90 percent of the available nights," says Nelson, professor of astronomy and astrophysics at the University of California, Santa Cruz, and astronomer at UCO/Lick Observatory. "The astronomers who use it generally think it's a fabulous instrument. It's totally changing the way they tackle certain problems in astronomy."
Some of the latest results from the ten-meter Keck I will be presented today (June 13) at the 186th national meeting of the American Astronomical Society in Pittsburgh. They include the first convincing signs for a "brown dwarf," a not-quite-star long hypothesized by astronomers; evidence of well-formed rotating disk galaxies in the early universe; and a detailed spectrum of unusual objects along the line of sight to a distant quasar.
Within the last year, Keck also has hit the headlines for its role in watching Comet Shoemaker-Levy 9 dive into Jupiter; for measuring a temperature of the early universe consistent with the "Big Bang" scenario; for finding carbon ash from early stars in the distant reaches of intergalactic space; and for detecting the pull of dark matter within a dwarf galaxy orbiting our Milky Way.
Nelson and the observatory's engineers are seeking to refine Keck's image quality. On a typical night of scientific observations, the telescope's images are "excellent," Nelson says, with an image size of about seven-tenths of an arcsecond. However, when the team measures the images with optical tools on an engineering night, they see better resolution: Typical image sizes are about half an arcsecond. "That says there is something wrong, that our optical alignment is not as good on science nights," Nelson says. "The details are very subtle, but it's an important issue."
The researchers also hope to improve the "phasing" of Keck's 36 mirror segments--the height of the edge of one segment relative to another. Ideally, that height should not exceed 40 nanometers, about 25 times smaller than the wavelength of light at one micron. Currently, alignment techniques are as good as 20 nanometers, but the alignment varies with telescope elevation angle due to the changing effects of gravity. "Phasing all of the mirrors has been done," Nelson says, "but we still have work to do to make it generally available to the observer."
About 250 feet from Keck I, Keck II is taking shape. The building and dome are complete, the telescope has been erected, and the cell that will hold the mirror segments is in place. By November, Nelson expects, the first 12 segments will be ready for a "first light" test, with all 36 segments in place by February 1996. Scientific observations could begin by October 1996.
"It's anybody's guess as to what will or won't work on Keck II, but we think progress should be faster because of our experiences with the first telescope," Nelson says. However, the roughly $10 million needed to combine images from Keck I and Keck II through interferometry--creating the resolution of a mirror 85 meters wide--is not yet in hand, he notes.
Finally, Nelson and his colleagues have designed an adaptive- optics system for Keck II and soon will start building it, largely with $6.3 million from the W. M. Keck Foundation. A computer will calculate distortions in earth's atmosphere from the flickers of a laser guide star invisible to the eye. Then, a six-inch flexible mirror with 350 tiny pistons will cancel those distortions. The resulting images will be about 20 to 50 times sharper in the infrared part of the spectrum. The challenges facing adaptive optics become far more daunting at the shorter wavelengths of visible light, Nelson says.
"Adaptive optics will make a lot of new science possible," he says, "but it is quite complex and has many limitations. It does not mean that we will no longer need telescopes in space."
Nelson will expand on these topics during a lecture on June 15, where he will accept the 1995 Dannie Heineman Prize for Astrophysics. The prize, awarded jointly by the American Astronomical Society and the American Institute of Physics, recognizes Nelson's work on both Keck Telescopes.
Editor's note: After the AAS meeting, you may reach Nelson at (408) 459-5132 or via e-mail at email@example.com. For more information about the Keck Observatory, contact Andrew Perala at (808) 885-7887 or firstname.lastname@example.org.