| Manu | Date: Monday, 13-December-2021, 9:57 AM | Message # 1 |
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| Five things to know about the James Webb Space Telescope
by Lucie Aubourg
Webb's centerpiece is its giant primary mirror, a concave structure 21.5 feet (6.5 meters) wide and made up of 18 smaller hexagonal mirrors.
The James Webb Space Telescope, the most powerful space observatory ever built, is finally set for launch in late December after decades of waiting.
An engineering marvel, it will help answer fundamental questions about the Universe, peering back in time 13 billion years. Here are five things to know.
Giant gold mirror
The telescope's centerpiece is its enormous primary mirror, a concave structure 21.5 feet (6.5 meters) wide and made up of 18 smaller hexagonal mirrors. They're made from beryllium coated with gold, optimized for reflecting infrared light from the far reaches of the universe.
The observatory also has four scientific instruments, which together fulfill two main purposes: imaging cosmic objects, and spectroscopy—breaking down light into separate wavelengths to study the physical and chemical properties of cosmic matter.
The mirror and instruments are protected by a five-layer sunshield, which is shaped like a kite and built to unfurl to the size of a tennis court.
Its membranes are composed of kapton, a material known for its high heat resistance and stability under a wide temperature range—both vital, since the Sun-facing side of the shield will get as hot as 230 degrees Fahrenheit (110 degrees Celsius), while the other side will reach lows of -394F.
The telescope also has a "spacecraft bus" containing its subsystems for electrical power, propulsion, communications, orientation, heating and data handling; all told, Webb weighs around as much as a school bus.
Read more/full article/source - https://phys.org/news/2021-12-james-webb-space-telescope.html
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