Kicking Off the GMT

Sally B. Patterson

The laboratory in the underbelly of the University of Arizona’s football stadium was the site of an unusual kickoff this summer as researchers got started on what could be a half-billion-dollar project. The goal was not a mere touchdown but an enormous skywatcher — the Giant Magellan Telescope (GMT) — that is scheduled for service in 2016.

The players included researchers from the eight institutions collaborating on the project. They gathered to observe the casting of the first of seven 27-ft-diameter mirrors that will be arranged to comprise a collecting surface 4.5 times larger than any current telescope.

The team filled an outsized mold with 40,000 pounds of borosilicate glass and heated it to around 2150 °F. As its specially designed 30-ft furnace slowly rotated, the molten glass seeped dow to fill 1681 hexagonal cores in the mold, forming a honeycomb mirror blank with a parabolic surface. The honeycomb structure was designed to lower the weight to about a fifth of that of a solid mirror of the same dimensions.

Next the researchers will tackle polishing and testing the mirror to prove that it works and — they hope — to secure the funding to continue work on the giant device. The GMT may never make the Super Bowl, but it could become a most valuable player in the search for alien planets and the investigation of dark energy.