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How the World’s Largest Telescope Will Hunt for Alien Life

The European Extremely Large Telescope has just been greenlit for construction.

by Becky Ferreira
Dec 11 2014, 11:00am

​Concept drawing of E-ELT. Image: ESO/L. Calçada

​Over the next decade, a new class of super-giant ground telescopes will emerge onto the astronomical scene. By far the most most gargantuan of these projects is the aptly named European Extremely Large Telescope (E-ELT), which just secured its first phase of funding—a whopping 1.24 billion Euros (1.54 billion USD).

Currently scheduled to receive its first light in 2024, the E-ELT's primary mirror will be an unprecedented 39.3 meters (130 feet) wide, several meters larger than competitors like the Giant Magellan Telescope and the Thirty Meter Telescope.

From its perch in Chile's Atacama Desert, it will be able to detect the atmospheric composition of terrestrial planets and glimpse the first objects ever to shine in the universe, which have never been directly observed before.

How the competition lines up. Image: Cmglee.

"The bigger the telescope, the sharper are the images you can make," E-ELT astronomer Jochen Liske told me over Skype. "The E-ELT is by far the largest. It will have an edge over all the competing projects."

The telescope will be an especially significant player in the search for extraterrestrial life. Space and ground telescopes alike have been identifying and characterizing exosolar planets for decades, but E-ELT has the potential to zoom in on the most tantalizing candidates with unmatched precision.

"This investigation might be most fun and most promising if you do it on a rocky, Earth-like planet around a solar type star, where the planet is also at the right distance from its star," explained Liske. "To do that, you simply need a very big telescope. There's just no way around it."

Other telescopes can make similar exoplanetary observations up to a point, but astronomers need to achieve very high angular resolution to study planets similar to our own. If an alien astronomer was trying to image Earth from 20 light years away, for example, it would be challenging to differentiate between the Sun's light and our planet's reflected glow.

E-ELT will be able to make that distinction, allowing it to detect biomarkers—like oxygen, methane, or water—in the atmospheres of terrestrial worlds. "That doesn't mean that you've identified little green men," clarified Liske, "it's just generally about the detection of life."

"That is the goal that we want to achieve in the long run," he continued. "It's going to take a few years, but we're pretty convinced we're going to find something in this way."

The E-ELT site in Chile. Image: ESO/S. Brunier.

The other major mystery the telescope may finally shed light on (or rather, collect light from) is the early universe, specifically by capturing a glimpse of the very first shining objects in the universe. The E-ELT and the James Webb Space Telescope (JWST) will team up to image these inaugural stars and galaxies, which have never been seen by any telescope before.

"This is an important chapter in the history of the universe that is observationally entirely unconstrained," said Liske "We know that period must exist, and we can set limits to when it must have occurred in the history of the universe. But we've not yet actually made those detections. That is certainly something where the E-ELT and the JWST are going to team up and work together to, first of all, detect them, and then also to characterize them."

The two telescopes complement each other perfectly. The JWST will be orbiting one million miles away from Earth in Langrangian point 2, equipped with a sunshield that will keep its mirror temperature at a chilly minus 388 degrees Fahrenheit. The cold mirrors make the JWST more sensitive to light than E-ELT, because it doesn't have to account for ambient radiation generated by warmer mirrors.

Meanwhile, the diameter of the E-ELT's primary mirror is about six times that of the JWST, which is 6.5 meters across. This size difference enables the E-ELT to achieve much higher resolution of the ancient objects that first lit up the universe.

"That's going to be how it splits up," explained Liske. "The JWST, with its higher sensitivity, will detect them first, and then—at least for the bright ones—we will be looking at these objects and trying to characterize them in more detail, using both high spatial as well as high spectral resolution."

The European Southern Observatory (ESO), the international organization behind the E-ELT, has at least a decade's worth of work to do before it captures the "let there be light" moment in the universe's history, or detects the first trace of alien life.

But the fact that it is now officially on its way bodes well for space research in the 2020s, and highlights ESO's ambition. Indeed, the E-ELT is actually a scaled down version of ESO's original plan to build a 100-meter-wide primary mirror, a conceptual design known as the Overwhelmingly Large Telescope.

Concept drawing of Overwhelmingly Large Telescope. Image: ESO Telescope Systems Division.

"No technical show-stoppers per se were uncovered in that study," Liske pointed out. "It just turned out to be very expensive, and there were also technical risks associated with it."

So, perhaps the E-ELT will one day find itself outclassed by an even more ambitious project, in the same way it is showing up so many telescopes today. For now, though, it's enough to look forward to 2024, when the world's largest eye on the sky is slated to finally open.