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The James Webb Telescope - unveiled by NASA
 
Artists conception of the James Webb Space Telescope
 
NASA unveiled the James Webb Space Telescope (JWST) last week. The largest and most expensive space telescope has been 20 years in the making, and is finally ready and the first significant pretest completed. The JWST is a joint project between NASA, the European Space Agency (ESA) and the Canadian Space Agency. “This was a long time coming, because it’s so complex,” explained NASA’s Administrator, Charlie Bolden. “Two decades of innovation and work and this is the result. We are opening a whole new territory of astronomy. We will see things that we’ve never been able to see before, because this telescope is much more powerful than even the great Hubble Telescope,” added John Mather, Nobel laureate and Senior Astrophysicist at GSFC’s Observational Cosmology Laboratory

So how is it different than Hubble and other space telescopes?
With a 21-foot wide mirror, the telescope is more than twice the size of the Hubble Space Telescope, with a light-collecting area five times as large. It is made of 18 highly sensitive gold coated-mirrors. To detect infrared light, the JWST will be cooled to around -220 degrees Celcius (-364 degrees F, just 50 degrees above absolute zero), and will need shielding from the sun. The final pieces of the telescope include sunshields that will protect the telescope’s infrared sensors from the sun’s background heat. Each sunshield is gold-plated and no thicker than a human hair. With $8.7 billion in construction and operations costs, it’s more than four times as expensive as its predecessor.
 
Comparison of JWST and Hubble Primary Mirrors
 
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