* Astronomy

Blobrana · L

RE: Giant Magellan Telescope

Blobrana · L

The Giant Magellan Telescope (GMT) Corporation is pleased to announce that nine astronomical research organizations from three continents have signed the Founders' Agreement to construct and operate the 25-meter Giant Magellan Telescope at Las Campanas Observatory in the Andes Mountains of Chile. In the United States the participating institutions are the Carnegie Institution for Science, Harvard University, the Smithsonian Institution, Texas A& M University, the University of Arizona, and the University of Texas at Austin. The two Australian members of the Founders group are the Australian National University and Astronomy Australia Limited. Most recently, the South Korean government has approved participation in the GMT project, with the Korean Astronomy and Space Science Institute as the representative of the Korean astronomical community.

Read more

Blobrana · L

The Giant Magellan Telescope (GMT) Consortium* announces that the GMT will be constructed at Cerro Las Campanas, Chile. This location was selected for its high altitude, dry climate, dark skies, and unsurpassed seeing quality, as well as its access to the southern skies.

This decision represents a critical step towards realizing our goal of building the premier next -generation astronomical observatory - Dr. Wendy Freedman, leader of the GMT Board and director of the Observatories of the Carnegie Institution, which operates Las Campanas.

The Giant Magellan Telescope represents the dawn of a new age of astronomical exploration. As telescopes get larger, we are able to see fainter, farther, and with more clarity than ever before. We can only predict a fraction of the scientific discoveries that will be made using this enormous telescope and the new insights into the universe that we will gain - Dr. Charles Al****, director of the Harvard-Smithsonian Center for Astrophysics.

The Las Campanas Observatory is home to the twin Magellan Telescopes, the predecessors of the new instrument.

The GMT builds on the partners collective experience in constructing and operating world-class telescopes. Locating the telescope at a proven world-class, mountain-top site in Chile will maximise its productivity and cost effectiveness - Prof. Nicholas Suntzeff, head of the astronomy program at Texas A&M University.

Excellent science has come from Las Campanas for several decades; the superb astronomical quality of the site is a significant contributor to this success - Dr. Wendy Freedman.

Scheduled for completion in 2016, the Giant Magellan Telescope will be the first of a new generation of ground-based telescopes. Its large size will offer exceptional resolving power, producing images up to 10 times sharper than the Hubble Space Telescope. The GMT will be composed of seven 8.4-meter primary mirrors, six of which will be off-axis encircling the seventh to produce a telescope with an effective aperture of 24.5 meters.

Read more

Blobrana · L

Giant Magellan Telescope
Over the past 20 years, a new generation of big telescopes has allowed astronomers to discover distant planets and galaxies. But those telescopes are runts compared to what's coming. Mirrors for what will be the world's largest telescope are now being made at the University of Arizona.
The Steward Observatory Mirror Lab recently began casting the first of seven mirrors -- each 27 feet in diameter -- that will become part of the Giant Magellan Telescope, creating an enormous reflective surface of glass.

The facility uses a unique process to cast single-piece mirrors so large. Twenty tons of glass are spun inside a two-story rotating furnace to create a naturally concave mirror. The bowl shape is highly effective at gathering and focusing light. As the glass melts, it flows around ceramic forms inside the furnace, creating a mirror a few inches thick on top of a glass honeycomb. That makes it just one-fifth the weight of a solid mirror.
Cooling the furnace will take almost three months. After that, the mirror will be moved to another room for polishing, a process that takes about a year. The finished product will be accurate to within one-billionth of a meter.

Eventually, the giant mirror will end up on a mountaintop in Chile, where it will join six others surrounding a seventh central mirror to become part of the Giant Magellan Telescope.
The Giant Magellan will have 10 times the resolution of the Hubble. Astronomers hope those powerful optics will help them look directly at some of the dozens of planets spotted orbiting other stars.

Source

Blobrana · L

The University of Arizona's Steward Observatory Mirror Lab is pre-firing its huge spinning furnace and inspecting tons of glass for casting a first 8.4-meter diameter mirror for the Giant Magellan Telescope (GMT). The casting is scheduled for Saturday, July 23.

With this milestone step, the GMT becomes the first extremely large ground-based telescope to start construction.

The completed GMT telescope primary mirror will consist of six 8.4-meter off-axis mirrors surrounding a seventh, on-axis central mirror.
(An off-axis mirror focuses light at an angle away from its axis, unlike a symmetrical mirror that focuses light along its axis.) This arrangement will give the GMT four-and-one-half times the collecting area of any current optical telescope and the resolving power of a 25.6-meter diameter telescope, or 10 times the resolution of the Hubble Space Telescope.

The Steward Observatory Mirror Lab casting team installs the last of 1,681 ceramic fibre cores to complete the mould for the first 8.4-meter diameter (27-foot) Giant Magellan Telescope mirror on May 26, 2005. Core installation took seven weeks. At this point, the mould holds 16,000 pounds of fibre tub walls, 15,000 pounds of cores and pins, and 17,000 pounds of tiles. About 40,000 pounds of Ohara E6 borosilicate glass will be loaded into the mirror. Bearings on the rotating furnace will turn a 100-ton load during spincasting on July 23, 2005. (Photo: Lori Stiles, University Communications)

'Spin-casting' single-piece telescope mirrors that are giant, stiff yet lightweight is an ingenious, awesome process that was conceived and developed by University of Arizona Regents' Professor of astronomy J. Roger P. Angel. Casting giant monolithic mirrors is accomplished at only one place in the world - the Steward Observatory Mirror Laboratory.

The casting team, headed by Randy Lutz, installed about 50 cores a day for a total 1,681 cores during seven weeks in April - May. The team bolted each core at precisely measured angles to hearth tile and adjoining cores in this operation. The crew daubed all the glued junctures with blue "smurf" - a concoction the colour of the blue smurf cartoon characters -- to prevent glass from sticking to the mould.

At this point, the mould holds 17,000 pounds of hearth tiles, 16,000 pounds in fibre tub walls, and 15,000 pounds of cores and pins. The casting team has now cleaned and inspected the completed mould, lowered the furnace cover into place, and begun pre-firing on June 16.

Team members actively 'pilot' the furnace by computer as temperatures ramp up during the first 8 days of the heating process, then shut power off to complete the two-week pre-firing. Pre-firing centres core glue joints, burns out any impurities and stresses the mould. The casting team will inspect the mould for any needed repairs after pre-firing.

Some of the most visually stunning steps in casting are glass inspection and loading. The team began inspecting 90 shipping crates of glass on June 24. Glass loading is scheduled for the second week of July, said Steve Miller, Mirror Lab manager.

The 40,000 pounds of borosilicate glass that will make the 27-foot diameter GMT mirror comes from Ohara Glassworks in Japan. Ohara made the glass from sand that comes from the gulf coast of Florida.

The Mirror Lab will start heating the furnace July 18. It takes six days for the glass to reach peak temperature at 2,150 degrees Fahrenheit (1178 Celsius). At this temperature, the glass begins to flow like honey at room temperature. The thick liquid glass flows between the hexagonal cores in the mould to create a "honeycomb" structure. The final honeycomb mirror blank will weigh about a fifth as much as a solid glass mirror of its size.

The bearings on the rotating furnace will turn a 100-ton load during spincasting. The furnace can be supplied with up to 1.1 Megawatts of electricity during casting -- enough to power an average 750 to 1,100 Tucson households, depending on the time of year.

The oven's rotation rate determines the depth of the curve spun into the shape of the mirror, or the mirror's focal length. The GMT mirror will spin 5 times a minute, slower than the two 8.4-meter mirrors the Lab made for the Large Binocular Telescope (LBT), because the off-axis GMT mirror is to be a shallower, longer focal-length mirror than the symmetric LBT primaries.

"This is a new epoch for astronomy. The fabrication of the off-axis mirror is a path-breaking event that will advance scientific discovery. Everyone in the eight-member GMT consortium is excited that we're in production." - Richard Meserve, president of the Carnegie Institution.

The Giant Magellan Telescope consortium currently includes the Carnegie Observatories, Harvard University, Smithsonian Astrophysical Observatory, University of Arizona, University of Michigan, Massachusetts Institute of Technology, University of Texas at Austin, and Texas A & M University.

"The fact that we are already in production is directly related to the successful technology developed for the twin 6.5-meter Magellan telescopes at Carnegie's Las Campanas Observatory in Chile. The Magellan telescopes have proved to be the best natural imaging telescopes on the ground." - Matt Johns, assistant director of the Carnegie Observatories and GMT project manager.

Mirror cooling is a carefully controlled process that will take 11 to 12 weeks. After the mirror is completely cooled, the lab will wash the ceramic cores out of the mirror's glass honeycomb cells. Then the mirror will be ground and polished to an accuracy of plus-or-minus 15 to 20 nanometres (a nanometre is a billionth of a meter). The mirror will be coated with a layer of reflective aluminium only 100 nanometres thick at the observatory site.

The GMT is slated for completion in 2016 at a site in northern Chile. With its powerful resolution and enormous collecting area, it will be able to probe the most important questions in astronomy, including the birth of stars and planetary systems in our Milky Way, the mysteries of black holes, and the genesis of galaxies.

Detailed information about the GMT design and science goals is online at

http://www.gmto.org/