Big Glass

At the end of March I got to travel to Tuscon for the first time for a project in collaboration with the University of Arizona. Being an astronomer it’s a bit surprising I had never been to Tucson before since U of A is involved in many observatories and countless astronomical instrumentation projects (not limited to JWST-NIRCam, and Magellan-AO). Between the huge astronomy presence and the legendary tamales, I was excited for the visit. I was also looking forward to some warm weather and a change of scenery.

I was not disappointed.

As a part of my trip, my collaborator Jared Males was nice enough to give me a tour of the mirror lab, where the Giant Magellan Telescope mirrors are being built. GMT is part of a set of next generation “extremely large telescopes” (ELTs) that will be a few times larger in diameter than any ground-based optical telescope in use now (8-10m currently). GMT will have a 24.5m diameter. All of the ELTs will be made up of smaller mirror segments that form the full telescope surface. Each segment of GMT is 8.4m across.

And here they make the solid glass surfaces, braced from behind with a honeycomb structure to reduce the total weight. They assemble chunks of special glass over the ceramic honeycomb molding and melt it in a giant spinning furnace. The glass is cooled rapidly first, and then very slowly over months. After the mirror has been set it is polished to the correct specifications (the step shown above).

Needless to say, I was grateful for the tour. I am definitely on team big glass. My trip to Tucson was fun and productive. I even got to see some nearby nature at the Sonora Desert Museum. Driving out to the museum was breath-taking, where cacti characteristic of the Sonora Desert fill the landscape.