The Giant Magellan Telescope is getting a key milestone Saturday as it moves closer to becoming operational with the addition of a gigantic mirror, Space.com reported.

The mirror is 27 feet across and is the third of seven that will combine to create a mirror 80 feet across. The mirror alone will weigh 20 tons when completed. The mirror will go into a rotating furnace capable of reaching 2,140 degrees Fahrenheit at the University of Arizona's Steward Observatory Mirror Lab in Tucson.

The telescope is on schedule to be operational in 2020 and will have a resolution ten times more powerful than that of the famed NASA Hubble Telescope.

"Astronomical discovery has always been paced by the power of available telescopes and imaging technology," Peter Strittmatter, head of the Steward Observatory's astronomy department, said in a statement. "The GMT allows another major step forward in both sensitivity and image sharpness."

Click here to see photos of the Giant Magellan Telescope.

The mirrors will act as adaptive optics devices meant to make clear the normal blurriness caused by the Earth's atmosphere. Among other things, officials said GMT will be used to search for exoplanets and study black holes.

"We expect to be able to make observations and spectrographic studies of the first stars that formed after the Big Bang," Michael Long, vice president of GMTO Corp., the nonprofit organization based in Pasadena that is coordinating the Giant Magellan Telescope project, told the Los Angeles Times. "We'll be able to observe the earliest galaxies, as those stars assembled, and answer the question, when did black holes arrive? Did they arrive with the early galaxies or did they arrive later?"

Technicians will turn the furnace up to 2,000 degrees Fahrenheit plus to forge the mirror, but it will take about a year to polish it. When it is finished, the mirror will be 1/20 the wavelength of light.

"Let's imagine you took this mirror and you enlarged it to the physical size of the United States. The tallest mountain on that surface would be 1 inch tall," Long said. "So it's incredibly tight tolerances that have to be maintained, even when the mirror is in the telescope itself."