Long time no see

A new generation of super telescopes will soon probe the most distant heavens

Mirrors on the twin Keck telescopes measure 32 feet in diameter. The Magellan telescope mirrors will stretch 80 feet. (W.M. Keck Observatory)

CAMBRIDGE - Some possess names nicely capturing the spirit of discovery: the "Giant Magellan," for example.

Others have appellations only a committee could love: Europe's "Extremely Large Telescope," most thuddingly.

Some may join Galileo's 20-power spyglass, the Palomar Observatory's legendary Hale 200-incher, or the space-borne Hubble as telescopes that magnificently enlarge humanity's view of the universe. Others will not see the light of day, never mind the light of stars - strangled in the conceptual crib as too costly or too narrowly conceived.

Within the next decade or so, a new generation of Earth- and space-based telescopes should be probing the farthest, faintest regions of the heavens, putting sharp focus on the formation of the first stars and galaxies. These monsters, many times more powerful than today's telescopes, should also bolster the hunt for habitable - or, indeed, inhabited - planets beyond the solar system and even beyond our Milky Way galaxy.

"We're reaching a wall on what we can learn with existing telescopes," said Wendy Freedman, director of the Observatories of the Carnegie Institution, one of the research bodies involved in development of the Giant Magellan. "It's time to take the leap to the next generation."

The telescope grabbing the most wows is NASA's James Webb Space Telescope, a $4.6 billion contraption whose 22-foot diameter honeycomb mirror will ride Aladdin-like atop a "carpet" of tennis court-sized sun shields meant to ensure that the telescope operates at a crisp minus-370 degrees Fahrenheit.

The Webb is billed as the successor to the Hubble Space Telescope, which suffers from technical aches and whose 8-foot main mirror is too puny to gather meaningful glimmers from primeval stars and the gases that gave rise to the original galaxies. The 17-year-old Hubble is still a marvel - astronauts are scheduled to undertake a repair mission next year, which could extend its life through the decade - as are such other existing space telescopes as the Chandra and Spitzer, but scientists are clamoring for newer, more powerful instruments.

The "seeing power" of telescopes is mainly a function of mirror size - the bigger the mirror, the greater the capacity to snare light from distant sources. "They are light buckets, basically," said Steve Maran, spokesman for the American Astronomical Society and a former NASA scientist. "The more light a telescope can collect, the farther back [in time] it can reach."

Telescopes are really time machines, trapping light that has travelled billions of years. Scientists theorize that the universe was forged in a single instant - the Big Bang - occurring 13.7 billion years ago. Non-optic instruments have captured the cosmic radiation signatures from the earliest moments of the universe, but an interlude starting perhaps as early as 300,000 years after the Big Bang and ending about 12.7 billion years ago - the universe's "Dark Age" - remains shrouded in space dust and deep mystery.

"This is when the first stars and galaxies were born," said Avi Loeb, a theoretical physicist at the Harvard-Smithsonian Center for Astrophysics. "All we see now are faint smudges on the nearest edges."

Loeb added: "At present, we have a family album that gives snapshots of the universe at infancy and as an adolescent. But we're missing the pictures from childhood. The Webb should give us images of first light forming in the first galaxies."

Scientists hope to find answers about how stars, galaxies, and black holes coalesced from the elementary particles of the early universe. They expect the new fantastically distant views will also yield clues about the nature of dark matter and dark energy, weird substances that pervade the cosmos.

The Webb, scheduled for launch in 2013, will maintain a fixed position relative to Earth some 1 million miles into space - making the Hubble seem like a homebody in its close orbit of only 355 miles. Webb's infrared telescope is designed to detect the faintest ghosts of galactic light, but infrared works best in deep darkness and intense cold. So the Webb will "park" at the Lagrange point, named after an 18th-century French theoretician, where gravitational pull from the Earth and Sun are equal, allowing it to remain in a steady orbit while providing optimal conditions for the equipment.

If astronomers are thrilled by the Webb, they also issue cautions. Maran noted that the Webb, with its emphasis on the infra-red spectrum, might prove less of a crowd-pleaser than the Hubble. "It may not be the source of equally mind-blowing images," he said.

For such pics, look to a new breed of giant ground-based telescopes with multiple times the light-gathering capacity of today's biggest observatories. "In some ways, the most exciting stuff in space will be happening on the ground," said Freedman. "Expect big new discoveries."

For nearly 50 years, starting in 1948, it was believed that the 200-inch mirror of the Hale telescope in California's famed Palomar Observatory had achieved the outer limits of what was possible for a land telescope. In the 1990s, technological advances in metallurgy allowed for the building of large but relatively lightweight new mirrors with computer-adjusted supports to prevent sag.

The biggest "eyes" scanning the cosmos at present are the twin Keck telescopes atop Hawaii's dormant Mauna Kea volcano, each with a mirror 10 meters in diameter, or about 32 feet. Until quite recently, it was assumed that atmospheric interference made it pointless to build larger telescopes - distortion caused by air molecules would offset gains in light-gathering capacity. A once-classified technology called "adaptive optics," however, uses laser lights bounced off sodium layers high in the skies to erase the "twinkle" effect that so bewitches ordinary folk but blurs the view for astronomers.

Space telescopes perform even better, with no atmospheric distortion and less "glare" from certain spectrums, but carry boggling price tags. Giant Earth telescopes, costing $1 billion, more or less, to build and operate for 20 years, seem a relative bargain. At least three such mammoth instruments are in various stages of development in North America, Europe, and Australia. Each is backed by organizations eager for the prestige such a telescope could bring, but a feral behind-the-scenes fight for funding means that none of these projects is a sure bet.

The giant telescopes will scan vaster portions of the heavens than the smaller Webb and are intended to complement the space telescope, not compete with it - much as today's land telescopes team with the Hubble and other space mirrors.

The Giant Magellan is scheduled to catch "first light" atop Chile's Cerro Las Campanas in 2016. The first of the Magellan's seven primary mirrors has already been cast. These mirrors, with one at the center and the other six arranged around like petals on a daisy, will give the telescope an effective aperture of 80 feet.

The mirror's surface is being polished to an accuracy of 1 millionth of an inch in a massive laboratory beneath the University of Arizona's football stadium. The Magellan's images should be 10 times sharper than those of Hubble, say proponents. Backed by Harvard, the Carnegie, the Smithsonian Institution, and other august bodies, the project has raised $30 million toward an estimated $600 million design and construction cost.

The Thirty-Meter Telescope, championed by a consortium of US and Canadian universities, has raised $80 million toward a final cost that remains even fuzzier than its stellar targets. Boosted by advanced adaptive optics, this giant will consist of a 98-foot diameter mirror made of 492 individual segments. Supporters predict it will come online in 2016.

Europe's Extremely Large Telescope - downgraded from a more ambitious "Overwhelmingly Large Telescope" - will cost $1 billion to bring its 138-foot diameter mirror to bear by 2016.

These land giants are likely to be the last generation of Earth-based telescopes. Many astronomers expect that in two or three decades, technology will overcome the hurdle of prohibitive costs and devise enormous telescopes for deployment in space.

"Scientists are greedy, always hungry for more information," said Sara Seager, professor of earth, atmospheric, and planetary sciences at the Massachusetts Institute of Technology. "So some of us are already thinking beyond the next generation of telescopes, to the next generation after the next."