The sixth mirror of the Magellan telescope has just been cast. There is one more to go

By 2029, the Magellan Telescope (GMT) in northern Chile will begin to collect the first beam of light from the universe. As part of a new generation of instruments called “Extra Large Telescope” (ELT), GMT will combine the functions of a complex primary mirror, flexible secondary mirror, adaptive optics (AO) and spectrometer to achieve further observation and observation . More detailed than any previous optical telescope.
At the center of the telescope are seven monolithic mirror segments, each with a diameter of 8.4 m (27.6 ft), which will give it the resolving power of the primary mirror of 24.5 m (80.4 ft). According to a recent statement from the GMT Organization (GMTO), the Richard Caris Mirror Laboratory at the University of Arizona began casting the sixth and seventh parts of the telescope’s primary mirror (this will be completed in the next four years).
The seven mirror parts that make up the GMT are the world’s largest rigid integral mirror. In its final configuration, six off-axis segments will surround a central axis segment, giving it a main reflector that can collect light from a surface area of ​​368 square meters (approximately 1,200 square feet). It also has a resolution 10 times higher than the Hubble Space Telescope (HST).
“The most important part of a telescope is its condenser. The larger the mirror, the deeper we can see the universe and the more details we can observe. The unique primary mirror design of the Magellan Giant Telescope consists of the world’s largest seven-sided mirror. .
“The casting of the sixth mirror is an important step towards completion. Once put into use, the giant Magellan telescope will produce images ten times clearer than the Hubble Space Telescope. The discovery of these mirrors will change our understanding of the universe.”
The casting process takes place in the Richard F. Caris Mirror Laboratory, which is supervised by the University of Arizona in Tuscon, Arizona. It started with nearly 17.5 metric tons (38,490 pounds) of high-purity borosilicate glass (also known as E6 glass), which was then melted in the world’s only rotary furnace. This “spin casting” process heats the glass to liquefaction, which is why the segment has a special parabolic shape.
At the highest temperature (the event is called “high fire”), the furnace rotates at 5 rpm to heat the glass to 1,165°C (2,129°F) for about 5 hours. The sixth and seventh mirror sections will reach “high firepower” on March 6, 2021. Then, they will undergo a one-month “annealing” process, during which the spinning furnace will slow down to eliminate internal stress on the glass.
This will harden the mirror as it cools and last for another 1.5 months before reaching room temperature. Once cooling is complete, the mirrors will be polished for two years until their surface reaches an optical surface accuracy of a few nanometers (less than one thousandth of the width of a human hair). Buell Jannuzi, Director of UofA Butler Observatory and Dean of Astronomy Department said:
“I am very proud of how the Mirror Lab’s operations have adapted to the pandemic, which has allowed the talented members of our talented Richard Caris Carris Mirror Lab to safely continue to produce mirrors for the giant Magellan telescope.”
At present, the first two mirror parts have been completed and stored in the mirror laboratory, while the third to sixth mirrors are now in various stages of their production. The fifth mirror was cast in November 2017, while the fourth mirror has finished back polishing, and the third mirror has more than half completed (and reached 70 nanometer accuracy).
An eighth backup mirror is also planned, and the backup mirror will be exchanged whenever another mirror segment needs to be maintained. The mirror is a key part of the optical design. It enables GMT to obtain the widest field of view of any ELT telescope at the 30-meter (approximately 100 feet) level-such as the 30-meter telescope (TMT) currently in use at Mauna Kea, Hawaii building.
The secret of GMT lies in its unique optical design, which enables GMT to utilize every photon collected by the mirror (thus ensuring unprecedented optical efficiency). As the chief scientist Rebecca Bernstein of Greenwich Mean Time explained:
“This unprecedented combination of light-gathering power, efficiency and image resolution will enable us to make new discoveries in all fields of astronomy, especially those that require the highest spatial and spectral resolution (such as searching for other earths).”
“We will have a unique high-resolution ability to study planets. This is the key to understanding whether the planet has the same rocky composition as our earth, whether it contains liquid water, and whether its atmosphere contains the correct combination of molecules to indicate the existence of the key life.”
By the end of the 2020s, the completed mirror will be transported from Tuscon, Arizona to the Las Campanas Observatory in the Atacama Desert in northern Chile. This arid area is located at an altitude of 2500 m (8,200 ft) above sea level and is considered to be one of the best places for astronomy on earth. At this altitude, the sky is very clear, and the distance from the city ensures that there is almost no light pollution.
Most importantly, the stable airflow in the area makes the image exceptionally clear, and the location (in the southern hemisphere) allows the observatory to stare at the center of the Milky Way. It is close to other observatories in the area (observing at other wavelengths) and can easily collaborate.
These will include the European Very Large Telescope (EELT), currently being built by the European Southern Observatory (ESO) at Cerro Amazones Observatory near Chile. It will also assist observations conducted by ESO at other major observatories in the area, such as the Very Large Telescope (VLT) and the Atacama Large Millimeter/Submillimeter Array (ALMA).
In addition to having 10 times the observation power of the Hubble Telescope, GMT also has four times the power of the highly anticipated James Webb Space Telescope scheduled for launch on October 31, 2021. Once put into use, GMT will explore the mysteries of the universe, including the early history of the universe, the role of dark matter and dark energy in the evolution of the universe, and the potential habitability of nearby exoplanets.
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Post time: Mar-16-2021