International consortium approves construction of Giant Magellan Telescope

The GMT project has institutional partners in Australia, Brazil (represented by FAPESP), South Korea, the US and Chile.

By Elton Alisson

Agência FAPESP – The Board of Directors of the Giant Magellan Telescope Organization (GMTO) announced in June that it has decided to start the first stage of construction of the mega-telescope in the Chilean Andes.

The decision was made after the consortium’s 11 international partners, including FAPESP, committed more than US$500 million to begin construction of the first of a new generation of extremely large telescopes.

The project is a global scientific collaboration with institutional partners in Australia, Brazil (represented by FAPESP), South Korea and the United States, as well as its host nation Chile. The estimated cost is about US$1.05 billion.

FAPESP will invest US$40 million, equivalent to approximately 4% of the project’s estimated cost. This investment ensures that researchers from São Paulo State will have 4% of the GMT’s operating time for their own observations, as well as giving Brazilian astronomers a seat on the consortium’s board.

“This first stage of the project is crucial,” said João Evangelista Steiner, a professor at the University of São Paulo’s Institute of Astronomy, Geophysics & Atmospheric Sciences (IAG-USP) in São Paulo State, Brazil, told Agência FAPESP. “It calls for construction of the mechanical structure and the start of scientific operations, with at least four of the telescope’s seven giant primary mirror segments in working order.”

Work began on the optical systems even before construction of the observatory started, Steiner explained, because the mirror is the key component and presented a major technological challenge.

Fabrication of the first mirror segment, with a diameter of 8.4 meters, was completed and approved in 2012. Only then did groundwork begin for preparing the construction site for the observatory on Las Campanas Peak, more than 2,500 meters above sea level in Chile’s Atacama Desert.

“The mirror segments were already being fabricated,” Steiner said. “The first is ready, and the second and third are about to be ground and polished. The fourth will be cast later this year.”

Work will now begin on construction of the foundations for the observatory, a huge pier on which the telescope will be erected and the telescope’s enclosure, according to Steiner. The enclosure will be a rotating cylindrical structure with shutters and screens that will shield the telescope from heat during the day, as well as from wind and storms, and will open at night for scientific operations.

A summit support building and other facilities will also be built to house equipment, offices, laboratories and utilities.

In parallel with construction of the observatory, fabrication of the first four mirror segments will be completed, and an initial set of scientific instruments will be produced, including cameras and spectrographs to measure the composition and movement of distant planets and galaxies. The telescope is expected to see first light in 2021.

Following completion of the first stage, another US$500 million funding tranche will be required to fabricate the other three mirror segments, scheduled for installation until 2024; develop an adaptive optics system; and produce the other scientific instruments needed for full operation of the GMT. However, “The telescope can start operating with four mirror segments while the others are being completed,” Steiner said.

Mirror fabrication

The seven mirror segments are being cast in the United States at the University of Arizona’s Steward Observatory Mirror Lab, the only facility in the world capable of creating mirrors of this size. The University of Arizona is one of the GMT’s international partners.

Each segment will weigh approximately 17 tons. It will take a year to mold and cool the ceramic glass, followed by three more years to grind and polish its surface. The seven segments will form the telescope’s primary mirror, with an effective aperture of 25.4 meters. It will collect more than six times the amount of light captured by the largest optical telescopes now in operation, producing images ten times sharper than those generated by the Hubble Space Telescope.

The GMT will enable astronomers to investigate the formation of stars and galaxies shortly after the Big Bang, measure the mass of black holes, and map their immediate vicinity.

It will also help scientists discover and characterize planets orbiting around other suns, detect exoplanets similar to Earth, and study the nature of dark matter and dark energy.

“The GMT represents a new reality compared with today’s optical telescopes,” Steiner said. “The funding necessary to start the first stage of the project was completed when FAPESP joined the consortium at the end of 2014.”

Researchers from São Paulo State will participate in the GMT along lines similar to their collaboration in the Gemini observatories, which began operating in 2000 with “twin” telescopes, one in the Chilean Andes and the other in Hawaii, and in the Southern Astrophysical Research (SOAR) telescope, which saw first light in 2004. Brazil has a 6% share in observations via Gemini, whose telescopes are equipped with primary mirrors 8.1 meters in diameter, and a 30% share in SOAR, which has a 4.2-meter mirror.

In addition to the GMT, two other giant telescopes are being developed internationally: the European Extremely Large Telescope (E-ELT), coordinated by the European Southern Observatory (ESO), and the Thirty Meter Telescope (TMT), run by the California Institute of Technology and the University of California.

To read more about the GMT, visit www.gmto.org.