Telescopes Have Grown from Huge to Humongous [Slide Show]
The next-generation, gigantic land-based telescopes are under construction, and they utterly dwarf their predecessors
![Telescopes Have Grown from Huge to Humongous [Slide Show]](https://static.scientificamerican.com/sciam/cache/file/C8092AE1-E8B7-4502-A05FD3B687CC30C8.jpg?w=590&h=393)
Telescopes Have Grown from Huge to Humongous [Slide Show]
- THE FIRST WAVE The Mount Wilson Observatory in California hosts two of the earliest significant, large ground-based telescopes. From 1917 to 1948 the 2.54-meter Hooker Telescope, funded by the Carnegie Institution of Washington, was the largest ground-based telescope in the world. Edwin Hubble used it to discover that not only did the universe extend beyond the Milky Way Galaxy but that it was still expanding. The Hale Telescope atop Mount Palomar, seen here, was completed in 1948, with funding from The Rockefeller Foundation. At 5.1 meters, it dethroned Hooker as the largest telescope; it kept that title until 1976. Hubble served as its director. Both telescopes are still in use today. Credits: Palomar/Caltech
- BIG BUT BUMBLING The BTA-6 is huge indeed, but it shows that bigger isn't always better. It was built by the Special Astrophysical Observatory of the Russian Academy of Sciences and was the first to utilize the now-standard two-axis altazimuth mount that lets the telescope move along both horizontal and vertical axes. Although it achieved first light in 1975 and began scientific observation in 1976, it never reached its optimal operating ability due to its poor location and relatively shoddy construction. Tyavin Paul/Wikimedia Commons
- TWIN TELESCOPES The twin 6.5-meter Magellan Telescopes at the Las Campanas Observatory in Chile saw first light in 2000 and 2002. They were built by the Carnegie Institution for Science, with help from Harvard University, Massachusetts Institute of Technology, the University of Arizona and the University of Michigan. The second Magellan Telescope, named for Landon T. Clay, hosts the Magellan Planet Search Program, which utilizes a spectrograph to hunt for exoplanets amongst about 400 stars.
- PRODUCTIVE POWERHOUSE The four 8.2-meter telescopes that make up the Very Large Telescope are second only to the Hubble Space Telescope in productivity. Located in Chile and operated by the European Southern Observatory, the first of the four telescopes saw first light in 1998. The four units can be used together for extremely high-resolution observations but are typically used individually. Like the space-based Hubble, the VLT has an eye for studying exoplanets, although that's certainly not the only thing it observes. The gas-giant Beta Pictoris b was discovered using the VLT in 2008, making the VLT the first telescope to snap an unquestionable image of an exoplanet. Credit: ESO/S. Brunier
- SUM OF ITS PARTS Although Keck 1 saw first light in 1990, it wasn't until 1993 that it truly began its scientific observations. It was joined by its twin, Keck 2, in 1996. Both were constructed on Mauna Kea in Hawaii, the planned site for the future Thirty Meter Telescope proposed by the same group. Designed by the University of California and Lawrence Berkeley National Laboratory with funding from Howard B. Keck, the observatories showcased a major breakthrough in how telescopes were built: Their 10-meter mirrors comprised smaller segments working together to gather light, rather than one very large (and thus difficult to manufacture and transport) mirror. Although each is smaller than today's record-holding largest telescope, the 10.4-meter Gran Telescopio Carnarias, the two Kecks combined can collect slightly more light.
- CURRENT GIANT With a 10.4-meter segmented primary mirror, the Gran Telescopio Canarias in the Spanish Canary Islands is currently the largest single-aperture optical telescope in the world. It took seven years to build, and saw first light in 2007, although science operations did not truly begin until 2009. More than 1,000 people were involved in planning the massive telescope, representing the University of Florida, the National Autonomous University of Mexico, the Institute of Astrophysics of the Canary Islands and other Spanish and Mexican institutions. Credit: Pachango/Wikimedia Commons
- STARTING THE NEXT ERA The Magellan Telescopes at the Las Campanas Observatory in Chile will get a massive sibling in the early 2020s. The Giant Magellan Telescope will be made of up seven large mirrors, which will work together to form one massive mirror that is effectively 24.5 meters--about four times the size of the existing Magellans. Three of the seven mirrors have already been made, and it can start operation with as few as four mirrors. The Carnegie Institution for Science is building this telescope, along with its partner organizations that make up the Giant Magellan Telescope Consortium.
Credit: Giant Magellan Telescope--GMTO Corporation - NEXT-GEN CONTROVERSY Sponsored by Caltech and the University of California and built by the same consortium as the Keck Telescopes, the in-progress Thirty Meter Telescope has found itself at the center of controversy. Its planned location is atop the Hawaiian mountain of Mauna Kea, a popular site for astronomical observation due to its ideal conditions--among other traits it boasts dark skies, low humidity and a nearly equatorial location. Although its estimated first light is the early 2020s, native Hawaiians protesting against the overuse of Mauna Kea, which they believe is a sacred site, have delayed the telescope's construction.
Courtesy TMT International Observatory - WITHIN REASON In the mountains of northern Chile the European Southern Observatory is building the aptly named 39.3-meter Extremely Large Telescope, which should see its first light in 2024. At almost four times the size of the largest existing telescope, it will be able to probe exoplanetary atmospheres, perhaps even investigating a handful of potentially habitable worlds around nearby stars.
Credit: ESO/L. Calçada - A REAL NIGHT OWL The Overwhelmingly Large Telescope first envisioned by the European Southern Observatory truly lives up to its name. Charmingly nicknamed the OWL, it would be a staggering 100-meters across. Due to its incredible size, it would need to utilize a segmented mirror. Although it was deemed possible, its cost of about $1.6 billion was as overwhelming as its size, so ESO chose to focus on the comparatively smaller and less costly Extremely Large Telescope. Another massive telescope proposal is the Colossus Telescope, which would utilize 60 eight-meter mirrors that would give the resolution of a massive 77-meter one. Both proposed telescopes have cast an eye toward studying Earth-like exoplanets as well as studying star formation and the earliest epochs of the universe's history. Credit: ESO
