Sailesh Acharya
HOD science

Webb telescope!! Why?

Before JWST started sending pictures back to Earth in July 2022, we at RG were desperately waiting and talking about the mission. Learners in grade IX were so curious about the science behind the telescope that they decided to build a scaled-down replica of JWST in early February. I was very impressed by the mirror assembly they designed, I have kept it in the science lab as a memento. During Open House 2022, a team of students stationed outside the science lab explained what JWST was and what was expected of it to the visitors. 

Every time young learners enter the lab, their eyes are fixated on the mirror assembly on the wall and some casually ask what that is. Answering it with a story from February 2022 fills me with nostalgia every time. We still talk about the important achievements and scientific discoveries that JWST has made, once in a while with our children. It is very gratifying when young Rajarshians peacefully listen to what I say about it. I consider the arms raised with curiosity during such sessions as my best achievement so far.

Images from Open House 2022 with a team that built the JWST replica

Telescopes have been an integral part of scientific discoveries. Hypothesis relating celestial bodies were proven and natural laws have been established since its invention in the early 16th century in the Netherlands. 

The whole technology behind observing the universe relies mostly on electromagnetic waves. You may question, was it not light that you said earlier this year? Yes, it is light and please keep in mind that light is also a part of the electromagnetic spectrum. Light from stars and planets reach us and hence we can see them. But it is not just visible light that a star or a celestial object emits. The radiation ranges in wavelength from radio waves to gamma rays. Visible light is a tiny portion of this bigger EM spectrum.C:\Users\Arjun\Desktop\yu1w_rple_201208.jpg

Complete EM spectrum, Credit: brgfx,

Because the universe is incomprehensibly massive and even light takes eternities to go from one end of the universe to the other, we can consider Webb as a big mirror that is capable of showing us what the universe used to look like in the past. The furthest objects are so far that the light emitted from them when they were formed has yet to reach the earth. The age of the universe is approximately 13.8 billion years. While the Hubble telescope can look back at the universe roughly 500 million years after the Big Bang, JWST can go further and see nearly 200 years after the Big Bang. This helps us understand how the universe evolved and what will be the fate of our universe.Timeline of the Universe infographic

Timeline of the universe, Credit: NASA, ESA, CSA and STScl, 

The other exceptional capability of the Webb telescope is to analyze the atmosphere of exoplanets. The radiation from the stars behind the planet passes through the atmosphere. The atoms and molecules present there absorb specific wavelengths. When we capture the radiation and study the spectrum, we find the missing wavelength which appears as a black band as shown in the image below and can tell the exact composition of their atmosphere. This can be used to look for biomarkers (Usually compounds produced only by living organisms) and study the possibility of alien life.       An image of the full spectrum of visible light - the rainbow - with dark lines appearing in the red, orange-yellow, and green-blue areas of the spectrum. These dark lines indicate that these specific wavelengths are missing and can be aligned to the elements that absorb these specific wavelengths - hydrogen, sodium, and magnesium.

Absorption spectra, Credit: NASA,

We have been showered with hundreds of unseen images of nebulae, stars, planets, exoplanets, and megastructures (which are still beyond our understanding) by the James Webb Space Telescope. But understand this, Webb isn’t like our conventional telescopes. The furthest objects are not even visible to us, the radiation that Webb’s mirror assembly receives is infrared and we cannot see in infrared. The received data (wavelength of the radiation) is processed by computers to produce an image, which is what that object looks like. Complex mathematical algorithms are used for this post-observation process and of course, huge processing power is required.

 Image 1: Uranus captured with NIRCam, Image 2: Crab nebula by Webb’s NIRCam and MIRI, Image 3: Jupiter with NIRCam, Image 4: Supernova 1987A with NIRCam, Image 5: Saturn with its rings and moons by NIRCam

Image credits: NASA, ESA, CSA, and STScl,

The argument persists and people will never stop saying it was not a worthy investment, but to those individuals who have been in love with the mysteries of the universe, it is by far the best investment of 10 billion dollars ever.   

Sailesh Acharya

HOD science         


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