Monster Telescopes!

For decades after its dedication in 1948, the famed 200-inch Hale reflecting telescope at Palomar inCaliforniareigned supreme as the world’s largest telescope. (Russiahad built a somewhat bigger one but it never performed as hoped.)  Then came the twin 400-inch scopes at the Keck Observatory inHawaii, twice as big as Hale. But now, two instruments are in the works that will absolutely dwarf all those that have come before them!

While both funding and technical issues have yet to be resolved, if all goes according to plan the world’s two largest telescopes will make their appearance on the astronomical scene within the coming years. And these new instruments aren’t going to be just a bit bigger than their predecessors. We’re talking really BIG!  The one will be five times and the other eight times as large as Palomar’s 200-incher!

The smallest (!) of the two is the Giant Magellan Telescope of the Carnegie Observatories (which operates Palomar along with Caltech).  Hailed as the “Dream Machine,” it will consist of seven individual mirrors each 330-inches or more than 27 feet across! Combined, they will give this behemoth an effective aperture of 1,000 feetand a resolving power 10 times that of the Hubble Space Telescope! Being technically unfeasible (most optical engineers would say “impossible”) to make one single glass mirror in such unprecedented sizes, nearly all large telescopes today have taken advantage of high-speed computers, electronic imaging and laser technology to bring the images from a grouping or mosaic of separate mirrors to a single focus (an amazing achievement!). This seven-eyed giant will truly be a wonder to behold when it eventually goes into operation.

Enormous as the Magellan will be, there’s an even larger telescope in the works. Called the European Extremely Large Telescope, it’s being built by the European Southern Observatory for its existing mountaintop site inChile. Its “segmented” primary mirror will consist of 798 individual hexagonal ones working together as a single unit. (The 400-inch primaries of the Keck telescopes are also segmented, being made up of individual mirrors joined together.)  This will result in an instrument with an effective aperture of nearly 1,600 inches—about half the size of a football field!

It should be mentioned that there’s a third monster telescope that’s only being talked about right now (preliminary work has already started on the above two projects). A planned partnership of Caltech, theUniversityofCalifornia, and the National Optical Astronomy Observatory, this instrument would use a segmented mirror having 760 individual hexagonal ones and resulting in an effective aperture of nearly 1,200 inches.

When I look at the little 4-inch mirror in my Astroscan-Plus and think of all the marvels it shows in the night sky, I can only imagine what wonders these new telescopes with their monster mirrors will revel to astronomers.  It’s going to be utterly awesome!

—James Mullaney

Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing.