The case for adding new ground-based telescopes is compelling, astronomy experts say. But they cost $700 million to $1 billion apiece just to build.
Giant Magellan Telescope/Carnegie Observatories
In a lab beneath the University of Arizona's football field, scientists are painstakingly polishing a glass disk nearly 28 feet across – the first of seven mirrors that, when combined to form an enormous optical telescope, would help revolutionize ground-based astronomy.
The telescope would reveal the universe's youngest stars and galaxies. It would analyze atmospheres surrounding planets orbiting other stars. In our own solar system, it would allow astronomers to explore frozen orbs far beyond the orbits of Neptune or Pluto in the so-called Kuiper Belt.
Nor is the Giant Magellan Telescope (GMT), supported by a US-led international group, alone. Another US-led, international consortium is moving forward this month on an even larger optical telescope, the Thirty Meter Telescope (TMT), atop Hawaii's Mauna Kea.
And both groups are looking over their shoulders at the Europeans, who in April approved a site for the European Southern Observatory's Extremely Large Telescope (ELT), whose 40-meter light-gathering mirror would make it the largest of the three projects.
Even in an era of space-based telescopes, the case for more glass on the ground is compelling, astronomers say. The light-gathering mirrors on space telescopes tend to be relatively small compared with their ground-based counterparts. So they can't perform the detailed studies of distant objects as efficiently as the larger, ground-based observatories.