WASHINGTON – The casting process has begun for the fifth of seven mirrors that will make up the world’s largest telescope, the Giant Magellan Telescope Organization said Friday.
The GMT, which will be installed in the Chilean Andes and produce images that are 10 times sharper than those from the Hubble Space Telescope, will combine the light from seven 8.4-meter-wide (27.5-foot-wide) mirrors to create a telescope with an effective aperture 24.5 meters in diameter.
The process of casting these giant mirrors involves melting nearly 20 tons of glass in a spinning furnace, the GMTO said in a press release, adding that after the glass disk cools it is polished into its final shape using technology developed by the University of Arizona (UA).
“The result of this high-precision process is a mirror that is polished to an accuracy of one-twentieth of a wavelength of light, or less than one-thousandth of the width of a human hair,” the release said.
The project, inaugurated in 2015 and expected to be operational by 2021, will be used to study planets outside our solar system and analyze galaxy formation.
“We are thrilled to be casting the Giant Magellan Telescope’s fifth mirror,” GMTO President Robert N. Shelton was quoted as saying in the release.
“The Giant Magellan Telescope project will enable breakthrough discoveries in astronomy, and perhaps entirely new fields of study. With the talents of the team at the University of Arizona and across our entire community, we are taking the next step towards completing the seven-mirror GMT.”
The casting process, which will be carried out at UA’s Richard F. Caris Mirror Laboratory, involves heating blocks of low-expansion E6 glass from Japan’s Ohara Corporation to 1165 C (2129 F) for around four hours inside a revolving furnace until it liquefies and flows into a mold.
The glass is then carefully cooled for three months while the furnace spins at a slower rate.
The first GMT mirror was completed several years ago, while three others are at various stages of production at UA’s Mirror Lab.
The giant mirrors will eventually be transported to GMT’s eventual home at the Carnegie Institution for Science’s Las Campanas Observatory in the Chilean Andes, whose clear, dark skies make it an ideal astronomical site, the GMTO said.
“Creating the largest telescope in history is a monumental endeavor, and the GMT will be among the largest privately funded scientific initiatives to date,” said Taft Armandroff, director of the University of Texas at Austin’s McDonald Observatory and vice chair of the GMTO Corporation’s board of directors.