World’s Most Extreme Telescopes, Geographically Speaking


—Picture courtesy NASA/JPL-Caltech

Yesterday NASA successfully hurtled another telescope into the heavens: the Wide-field Infrared Survey Explorer, or WISE.

Judging from the plethora of news coverage, WISE has quite a few people pretty excited. After all, NASA has only a handful of operational space telescopes up there right now … roughly 15 by my count [and I challenge you to name more than three without Googling].

Given the newbie’s relatively short projected life span of ten months, I can only imagine that all the media hoopla is over WISE’s potential.

Mission managers are hailing the craft’s ability to scan the entire night sky in infrared with unprecedented detail, possibly helping us to discover new comets, asteroids, brown dwarfs—maybe even a new planet within our solar system.

Even with that provocative prediction, it’s hard to get some folk excited about NASA and their big-budget telescopes. Space can seem so remote and cold, and it can be a genuine challenge tethering the importance of astronomy to our earthly pursuits.

So taking a cue from my colleagues in the TV industry, I started wondering: What are some of the superlatives that apply to telescopes here on Earth that might put stars in even an astrophobe’s eyes?


For now, at least, the world’s biggest optical telescope is the Gran Telescopio Canarias on the Spanish-held island of La Palma in the Canary Islands.

The telescope’s segmented, honeycomb-like mirror has an aperture, or light-collecting potential, of 10.4 meters (34 feet).


—GTC photo by Pablo Bonet

For contrast, think of all the fantastic pictures we have from the Hubble Space Telescope, and it has just a 2.4-meter (7.8-foot) aperture!

But GTC might not hold its title for long. The Thirty Meter Telescope and the Giant Magellan Telescope are both U.S.-based projects aiming to create the world’s biggest optical telescope.

TMT is slated to join the cluster of domes on Hawaii’s Mauna Kea volcano, while Magellan is bound for the mountains of Las Campanas, Chile.

Meanwhile, in Europe, folks are hard at work on the aptly named European Extremely Large Telescope, a 42-meter (137.8-foot) monstrosity yet to find a suitable home.


—Photo courtesy of the NAIC – Arecibo Observatory, a facility of the NSF

Other than optical, the biggest single-dish radio telescope is the Arecibo Observatory in Puerto Rico.

The reflector dish, which is built into the ground to keep it from collapsing under its own weight, covers nearly 20 acres (8 hectares).


If climbing the highest mountain is more your style, you should try for a visit to the Llano de Chajnantor Observatory in Chile’s northern Atacama desert.

The site actually hosts several submillimeter telescopes, built on a plateau 16,667 feet (5,080 meters) above sea level.


—Llano de Chajnantor photo by Ricardo Bustos

(PS, submillimeter is a type of microwave radiation closest to infrared in the light spectrum. These low-energy waves help astronomers peer through otherwise opaque dust clouds to see, for example, how stars are born.)

The record for the highest optical telescope—aside from the ones in space, of course—has been held since 2002 by the Indian Astronomical Observatory, sitting at 14,800 feet (4,517 meters) above sea level in the Himalaya.


It’s easy to see why telescopes on the ground would try to match telescopes in orbit by getting bigger or going higher. But oddly enough, there are some Earth-based telescopes that do their jobs best by seeing how low they can go.

The deepest telescopes on Earth look for neutrinos—small uncharged particles that can come from nuclear reactions, such as those that happen inside stars, or from crashes among cosmic rays.

Neutrinos are *extremely* hard to detect, since they tend to pass right through normal matter without disturbing anything. For example, more than 50 trillion neutrinos from the sun pass through the human body every second.

Finding even a few means setting up detectors far from any sources of background radiation, usually surrounded by purified liquids.

Studying neutrinos means better understanding the sun, other stars, and maybe even the properties of mysterious dark matter.

There are two neutrino telescopes that could vie for the title of deepest telescope: The Baikal Deep Underwater Neutrino Experiment in Siberia’s Lake Baikal, and the Super-Kamiokande (or Super-K) neutrino observatory in Japan.

Technically Baikal is deeper at about 3,900 feet (1,200 meters) below sea level, but it’s more an array of probes set up in a lake than its own custom-made facility.

By contrast, Super-K is a huge, human-made water tank lined with glass tubes that was built about a mile (1.6 kilometers) under a Japanese mountain.


And finally, what would any explorer’s guide to extreme telescopes be without a visit to an observatory that requires long arduous treks and polar gear?


—Photo by Bradford Benson, NSF

While most observatories set themselves up far from city lights, it’s hard to top the distances astronomers must travel to use the NSF-funded South Pole Telescope in Antarctica.

The observatory lies on an ice sheet about 11 hours away by plane from the nearest major city.

It’s cold, it’s isolated, and it’s a great place to look at the universe via millimeter and submillimeter light, searching for distant galaxy clusters or analyzing the radiation afterglow of the big bang.