NASA explains why the James Webb Space Telescope uses ‘salty’ lenses


As NASA completes all major deployments of the James Webb Space Telescope and the observatory enters a “cooling off period,” the agency is sharing some fun facts about the $10 billion (approximately Rs. 74,100) observatory. These include some lentils, which are made of salt. But why does this infrared telescope need a “salty” lens? In a new video, scientists working on the telescope shared why salt is vital to the space observatory. And the James Webb Telescope uses not one, but three types of saline lenses.

There are different types of lenses. Mirrors are reflective lenses that bend light, but there are some that transmit light. These second types of lenses are called transmissive lenses. For James Webb, infrared light, which behaves differently from visible light, plays a crucial role. The key here is: glass absorbs infrared light, but salt does not.

The narrator in the NASA video says, “Salts are more than something you sprinkle on your food.” A salt is a combination of a positively charged element and a negatively charged halide. They gain their charge by either losing or gaining a negatively charged electron. The salt we typically eat is sodium chloride, but that’s not the only type of salt. Some other types are: lithium fluoride, barium fluoride, and zinc selenide.

However, in the long term, these lenses are threatened by space debris, including micrometeorites.

NASA Goddard Space Flight Center scientist Michelle Thaller said during a livestream that small impacts from micrometeorites are bound to occur. However, NASA scientists say they took this factor into account as the telescope is expected to last 10 years. They said they had contingency plans in place to deal with this inevitability.

The five layers of sun protection not only protect the telescope from heat, but also from dust and dirt. But a micrometeoroid can come from any side and damage any part of the telescope. If a mirror is damaged, this can be taken into account.

NASA launched the James Webb Space Telescope on December 25 and has been working to deploy it in space for the past two weeks. It has completed key deployments such as primary and secondary mirrors.

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