The New York Times Student Journalism Institute

Beneath the University of Arizona’s football stadium, a massive, rotating red furnace sprouting wires and copper coiling heats 20 tons of molten glass.

On Saturday, it will reach roughly 2,150 degrees Fahrenheit, which is just hot enough for the glass to finish melting into the crevices of a huge honeycomb-shaped mold consisting of 1,750 hexagonal columns.

“I’m just terribly excited,” said Dr. David Lambert, director of the McDonald Observatory at the University of Texas at Austin. On Saturday he will join hundreds of people — astronomers, donors and interested citizens — in watching the furnace as it continues making the second of seven mirrors for what will be one of the world’s largest telescopes.

“I was there when they cast the first one,” Lambert said. “I’m delighted to be back for the second one, and I hope to be there for three, four, five, six and seven.”

The glass will be cooled slowly over the next 12 hours so that it won’t crack. After three years of grinding and precise polishing, the final product, a mirror 27 feet in diameter, will be complete.

The university’s Steward Observatory Mirror Lab, under the direction of Roger Angel, will produce the mirror. The lab has been making giant mirrors since 1980, but this one is special. When combined with six other mirrors, it will form the Giant Magellan Telescope, a $700 million project supported by universities and research institutes from the U.S., South Korea and Australia.

The telescope will be located in the Andes on a peak called Las Campanas in Chile. Sponsors hope to have the telescope completed by 2020, but so far they have raised only 40 percent of the cost of construction.

The size of a telescope is a primary factor in determining its sensitivity. The Giant Magellan’s mirrors will be capable of collecting light dating back to the beginning of the universe.

“It will dwarf anything in existence today,” said Dr. Rick Fienberg, press officer of the American Astronomical Society.

As the furnace below the stadium rotates, the centrifugal force pushes the saucerlike glass formation into a parabolic shape. The honeycomb structure allows the concave mirror to maintain its stiffness without the weight of a solid mirror.

After the mirrors are completed, at a cost of $20 million each, they will be placed in a hexagonal formation like flowers in a bouquet, with one mirror in the center. That structure, on top of a metal base, will channel starlight into a set of smaller mirrors correcting the distortion of the Earth’s atmosphere. The light will then pass through imaging processors to produce sharp pictures of stars and possibly their previously undiscovered planets, said Dr. Peter Wehinger, director of development at the lab.

Though scientists are moving forward with the casting of the mirror, the future of the telescope isn’t certain. Finding the remaining $300 million or $400 million needed to complete the project will be no easy feat, Lambert said. The public casting of the second mirror is being used to attract the attention of potential donors, including universities and the National Science Foundation. The first mirror was cast in 2005 and is now nearly complete.

The Giant Magellan Telescope is one of three large telescopes being developed. The European Extremely Large Telescope is set for completion in 2020, and the Thirty Meter Telescope, designed by scientists in California, is expected to be completed in 2018. Each has a different design.

Though there is competition among the three telescope builders, Wehinger said that when it comes to science, they are willing to share. “There’s a lot of space and time to explore,” he said. “And there’s enough room for more than one big telescope.”