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Supersize Me.

PROFESSIONAL ASTRONOMERS, just like amateurs, suffer from that widespread affliction known as aperture creep. If only we had a scope twice that size, they fantasize, think what we'd discover.

Chile's Las Campanas Observatory already hosts the twin Magellan Telescopes, each bearing a 6.5-meter (21-foot) mirror. But soon it will boast the Giant Magellan Telescope. This behemoth will combine seven 8.4-meter mirrors for an effective aperture of 24.5 meters (80 feet). The two 10-meter Keck telescopes atop Mauna Kea in Hawai'i do phenomenal science. Yet astronomers hope eventually to add another telescope just steps away with a mirror effectively 30 meters in diameter.

European pros might have the most pronounced aperture creep of all. The four unit telescopes (8.2 m each) that make up the European Southern Observatory's Very Large Telescope have conducted groundbreaking astronomy for more than a decade. But the ESO is now building the Extremely Large Telescope (39.3 m). If European astronomers had had their way, the ESO instead would be erecting the Overwhelmingly Large Telescope (100 m).

I'm not making these names up. One wonders what they'd dub the next iteration: The Astronomically Large Telescope? The Unimaginably Large Telescope? Suitable adverbs would run out long before their lofty notions.

This ever-bigger tendency is not limited to single-object observing. Large survey projects like the Sloan Digital Sky Survey (2.5 m) will pale, at least in terms of total data collected, beside next-gen survey instruments like the Large Synoptic Survey Telescope (8.4 m). The SDSS total data volume is about 40 terabytes; LS ST will gather 15 terabytes of raw data every night (S&T: Sept. 2016, p. 16).

Nor does "bigger is better" confine itself to optical and near-infrared astronomy. The Arecibo Observatory (305 m), for instance, recently ceded the distinction of world's largest single-dish radio telescope to China's Five-hundred-meter Aperture Spherical Radio Telescope, or FAST (500 m). Even space telescopes creep. The James Webb Space Telescope (6.5 m) will explore far more deeply than is possible with either the Spitzer Space Telescope (0.85 m)--which focuses on the infrared as JWST will--or the Hubble Space Telescope (2.4 m).

Creep is a good thing for astronomy, of course. Those three monster optical telescopes alone--the Giant Magellan, the Thirty Meter, and the Extremely Large--will revolutionize our understanding of the universe. So huge are they in significance that we're devoting two articles to them. The first, on page 14, describes the telescopes in general; the second, in next month's issue, goes into their instrumentation and the key science questions they'll help us address.

Amateurs: Isn't it reassuring to know you're not alone in your predicament?

Peter Tyson

Editor in Chief

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Title Annotation:SPECTRUM
Author:Tyson, Peter
Publication:Sky & Telescope
Date:Nov 1, 2018
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