Behemoths and First Light...

The European Extremely Large Telescope is under construction on Cerro Armazones, Chile. (Artist’s conception courtesy of ESO/L. Calçada.)
Citation: Phys. Today 68, 8, 24 (2015); http://dx.doi.org/10.1063/PT.3.2875

Topics: Astronomy, Astrophysics, Research, SETI, Telescopes

Among the science goals for three 30-m-scale telescopes is to seek signs of extraterrestrial life. But the big projects must first overcome big hurdles.

In what seems akin to winning the lottery, astronomers are moving ahead with not one, but three gigantic optical-IR telescopes, each with a price tag upwards of a billion dollars. The European Extremely Large Telescope (E-ELT) and the Giant Magellan Telescope (GMT) are both sited in Chile, and the Thirty Meter Telescope (TMT) is to be built on Mauna Kea in Hawaii.

For a given wavelength, the diffraction limit, which sets a telescope’s maximum possible resolution, shrinks as the primary mirror grows. “We will be able to take exquisitely sensitive images back to the beginning of the observable universe,” says TMT board member Michael Bolte of the University of California, Santa Cruz. With adaptive optics, the ground-based telescopes will have spatial resolution exceeding that of the Hubble Space Telescope by at least a factor of 10 and topping that of the 6.5-m James Webb Space Telescope (JWST), scheduled to launch in 2018.

The billion-dollar scale raises questions, says Matt Mountain, president of the Association of Universities for Research in Astronomy. “What are the appropriate funding models? It’s fair to ask if we have enough resources globally to build, operate, and adequately instrument three of these as completely independent entities.”

The science goals are similar for the three telescopes: They will be used to search for biomarkers in the atmospheres of extrasolar planets and to study black holes, dark matter, dark energy, star and galaxy formation, the era of re-ionization, and more. But the telescopes differ in design, instrumentation, approaches to adaptive optics, and funding and organizational structures.

Each project faces its own technical, financial, and social hurdles; in particular, the GMT still has half a billion dollars to raise, and some native Hawaiians strongly oppose the building of the TMT on a mountain they hold sacred. But to first order, says Jochen Liske, acting program scientist for the E-ELT, “The challenge for all three projects is getting things right and producing a telescope that works.” They all aim to have first light in the early to mid 2020s.

Physics Today: Behemoth telescopes build toward first light, Tom Feder