National Geographic : 2009 Jul
• astronomer propitiates the gods at the start of each Subaru observing run by pouring vintage sake on the ground outside the dome at the four points of the compass.) When a particular instrument is required, a robotic yellow trolley makes its way to the alcove, picks up the detec- tor, ferries it to the bottom of the massive tele- scope, and locks it in place, attaching the data cables and the plumbing for the detector s re- frigeration system. Subaru happens to be one of the few giant telescopes that anybody has ever actually looked through. For its inauguration in 1999, an eyepiece was attached so that Princess Sayako of Japan could have a look through the scope, and for several nights therea er eager Subaru sta ers did the same. "Everything you can see in the Hubble Space Telescope photos--- the colors, the knots in the clouds---I could see with my own eyes, in stunning Technicolor," one recalled. Keck consists of two identical telescopes. Both have ten-meter mirrors made of 36 seg- ments; with its support structure, each segment weighs close to a thousand pounds, costs close to a million dollars, and would su ce to create a ne, university-grade telescope on its own. e telescopes "tubes" are spindly steel skeletons that look as delicate as spiders webs but are more precisely con gured than a racing sloop s rigging. "We use the telescope s mission to mo- tivate ourselves," one Keck astronomer told me. "If a little wire or something is found intruding into the optical path, we think, If the light has been traveling through space for 90 percent of the history of the universe, and it got this close to the telescope, we d better make sure it gets the rest of the way." Few of the astronomers awarded time on the big telescopes actually go there to observe any- more. Most submit their requests electronical- ly---on a recent night at Gemini, the scheduled projects ranged from "Primordial Solar System Masses" to "Magnetic Activity in Ultracool Dwarfs"---and the results are sent back to them. Geo Marcy, a modern-day Prince Henry the Navigator whose team has dis- covered more than 150 planets orbiting stars other than our sun, gets more observing time than most at Keck but has not been there for years. Instead, his extrasolar planet team observes from a remote operating facility at UC Berkeley. During observ- ing runs, Marcy reports, "we settle into a rou- tine of working all night. We have all our books and other resources here at hand, plus enough normal life so our spouses don t forget us." their unprecedented light- gathering power, today s big telescopes bene t from their adaptive optics (AO) systems, which compensate for atmospheric turbulence. e turbulence is what makes stars glitter; telescopes magnify every twinkle. A typical AO system res a laser beam into a thin layer of sodium atoms 56 miles high in the atmosphere, causing them to glow. By monitoring this arti cial star, the system determines how the air is churning and adjusts the telescope s optics more than a thousand times each second to compensate. Gemini pays a pair of students ten dollars an hour to sit outside the dome all night, walkie- talkies in hand, ready to warn the astronomers to turn off the laser should an airplane ap- proach. "It s incredible to see in practice," says Scott Fisher. "When the AO system is o , you see a nice, pretty star that looks a little fuzzy. Turn the AO on, and the star just goes phonk! and collapses to a tiny point." Objects in the night sky are measured in A TELESCOPE DOESN'T JUST SHOW YOU WHAT'S OUT THERE; IT IMPRESSES UPON YOU HOW LITTLE YOU KNOW.