Seeing the Light of Long Ago

Las Campanas, Chile. The Magellan I telescope dome, above, will get its mirror in mid 1999 and open for business sometime in 2000. OCIW, FRANK PEREZ

Professor of astronomy Robert P. Kirshner '70 and others who measure the redshifts of very distant supernovas (exploding stars) may be on the brink of a transforming discovery. In 1929 Edwin Hubble found that the universe is expanding. Data released in 1998, by a team including Kirshner, strongly suggest something "very odd," he says, "but it might be true"--that the universe won't attain equilibrium or collapse inward in a Big Crunch, but expand forever. (In which case, The End Is Not Near.) Moreover, the spectra seem to say, the universe is expanding at an accelerating rate, hastening into infinity.

We shall see. Technicians at the University of Arizona Mirror Lab turned on the oven on September 9, 1998. By the fifteenth, 22,750 pounds of glass had melted and the 6.5-meter mirror for the Magellan II telescope was cast. It cooled in the oven until early December. Once ground and polished for 10 months and tested, it will go by truck and ship--a wide load--to Las Campanas, a site 7,800 feet up in the Chilean Andes. Magellan II will sit next to Magellan I, at left, and should be operational in 2002. Both telescopes will be able to see the ancient light of an explosion that occurred, say, seven billion years ago, light that has traveled at the speed of light and reached us only now.

Harvard is part of a consortium building the two Magellan telescopes at the Carnegie Institution of Washington's Las Campanas Observatory. Carnegie is a 50 percent partner; Harvard will put up 20 percent of the cost, the University of Michigan, the University of Arizona, and MIT 10 percent each. Harvard astronomers have access to Smithsonian Astrophysical Observatory telescopes in the Northern Hemisphere; now, "these telescopes in Chile will put us in a really good position," says Kirshner, who has been an enthusiastic fundraiser for the project. Both Magellan I and II are 6.5-meter-aperture optical/infrared telescopes, not the biggest on earth, but whoppers. (Much of this century's breakthrough astronomical work has been done on the 5-meter instrument at Palomar Observatory in California.) Harvard's $14-million share of the Magellan project buys 140 nights a year of telescope time.

Exciting nights. The prospect of getting behind the wheel of state-of-the-art technology, at a dark site with near-perfect weather in the Southern Hemisphere, makes Kirshner effervesce. The center of our galaxy lies in Sagittarius, and in Chile will pass overhead, instead of near the horizon. Around the center are globular clusters of stars, laboratories for studying how stars work, classrooms for learning the history of our galaxy.

Why build a telescope on land when we can now hurl them into space above the atmosphere? Telescopes in space cost a hundred times more than those on land. Kirshner cites two other advantages of staying down-to-earth. On land, all of the instrumentation that goes with a telescope can be kept closer to the cutting edge, whereas the technology of an instrument in space is frozen when the design is accepted. And telescopes on land can be much bigger--and better at light-gathering. "Astronomers are greedy for light," says Kirshner. "We need those photons."

~ Christopher Reed

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