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  • Sahil Bade

A Webb of Gold

You’ve surely heard of the James Webb Space Telescope. If you haven’t, how big is the rock that you’re living under?! But, do you actually know what it was built for? And why have they used so much gold to build it? We will explore all these things in this article.

This telescope was built to cater to a very specific reason: To study the formation of the first galaxies and the light from them. It was also built to find habitable planets because we humans are slowly killing the earth (figure of speech: personification). Other reasons are to study the origin of life and to study the formation of stars and nebulas. Okay, so that covers the question, “What was it built for?”. Now, why it is literally covered in gold?

Well, the gold, which is actually gold-plated beryllium, acts as a mirror, which reflects light into the central black box, called the Integrated Science Instrument Module, which processes the data and sends it back to earth. But why gold? Why not just stick a normal mirror? And why beryllium? To answer the first and second questions, the JWST’s mirror does not need to reflect visible light into the ISIM, it needs to reflect infrared light. Gold is one of the most reflective materials at the wavelength of infrared light.

What about beryllium? Well, as the JWST orbits the sun much farther away from the earth’s orbit, the temperatures there will be extremely, extremely cold. Specifically, it orbits through Lagrange point L2, which is 1.5 million kilometres away from earth (in comparison, Hubble’s orbit was only 570 kilometres away from earth). The mirrors need to still be strong enough to function. And they need to be light. On top of all of that, the maximum operating temperature of the JWST is only 50 Kelvin or -223° Celsius. So we need a material that is strong, lightweight enough to be launched by a rocket, and which can withstand very low temperatures. As you can probably tell, beryllium fits into the criteria extremely well.

That answers all the questions, imaginary-person-that-I-invented-to-make-this-article-less-boring. Thanks for reading this article.

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