On June 8, the magazine SPACE (6/8, Howell) reported about a proposed 77-meter Colossus telescope. I think the very first thing to do here is to attempt to put this into perspective. Currently, the largest ground-based telescopes in operation are the joint 10 meter Keck’s on Mauna Kea in Hawaii. These have been linked to provide interferometry in visible light wavelengths – a feat of extreme difficulty and delicacy. So, this proposed Colossus telescope would be 7.7 times the diameter of one Keck. Because the resolving power of a telescope increases as the square of its radius, this means that the Colossus telescope will have 59 times the resolution. This is a phenomenal difference. In terms of amateur telescopes, it is more than the difference between a 4″ telescope and a 28″ telescope. That difference provides only 49 times increased resolution. The Colossus is like comparing a 28″ dobsonian to a 3.5″ telescope, of the kind and size that Galileo had. This would enable us to see extrasolar planets from far distant solar systems.
If this Colossus telescope were properly funded, the article continues, the telescope could be constructed in mere five years, instead of the 15 to 20 years now commonplace for such research-grade telescopes. This is according to proposal team member Jeff Kuhn of the University of Hawaii’s Institute for Astronomy. The Colossus telescope would, then be large enough to detect a theoretical Dyson sphere around a star system if an alien civilization built one. A Dyson sphere is named for the physicist Freeman Dyson, who theorized it in the 1950’s. It is an enclosure built around a star, such that the enclosure absorbs all the energy output from the star, enabling it to be habitable. The size of the sphere depends on the temperature of the star, and the more massive the star, the larger the Dyson sphere would have to be. This type of structure was proposed long before extrasolar planets began to be discovered, and may have been posited as a means of furthering the belief that humanity is not the only intelligent species in the universe. Since extrasolar planets had not yet begun to be discovered at the time the Dyson sphere was proposed, any alien civilization would have had to live on the star itself.
Here is a photo of a proposed Dyson sphere:by