Back to the future 3 – the James Webb Space Telescope

At 5:49pm (IST) on Christmas day of 2021, NASA successfully launched the largest and the most powerful telescope ever produced – the James Webb Space Telescope (JWST)! Carl Sagan was once said to have been proud of the “Back to the Future” movie and had said that it depicted the science in it pretty well. Time has progressed and so has technology. So, the proverbial movie “Back to the Future 3” happened on Dec 25, 2021, just a week ago - in real life! The JWST was launched with the Ariane5 launcher from French Guiana. It was not just another launch. It was special and first in many ways. Carl Sagan also once said, “We can judge our progress by the courage of our questions and the depth of our answers, our willingness to embrace what is true rather than what feels good.” I am not privy to the context in which he was speaking, but we can relate the quote to the launch of JWST – because it is going to do precisely that – ask better questions and maybe redefine our understanding of the field if the answers are inconvenient. In science, we do that all the time!

You can Google about the JWST and find all the fun facts and trivia and indeed the serious science surrounding it. The point of this article is not to repeat it yet again, but instead to offer a different perspective.

Before we begin, let’s first understand what we are talking about. Why is James Webb space telescope named after James Webb? Who is he? Well, he wasn’t an astronomer like Hubble (Hubble space telescope has been servicing us with spectacular imagery past 30 years or so). James Webb was a government officer! He held together the fledgling NASA space program between 1961 and 1968 and worked towards ensuring the Apollo moon mission went ahead. This space telescope has been named after him, to honour his singular contribution to asking difficult questions and accepting uncomfortable truth, in pursuit of the unknown. So what is JWST? And what is the big deal?

In layman’s terms, JWST is as long and wide as a tennis court and is as high as a 3-storied building! Even the mighty Ariane5 could not have taken off with the telescope in this form! So the telescope was designed to be folded and will then be unfurled in space once it reaches its designated position. The idea of having a better telescope than Hubble had begun even as Hubble telescope was being launched. JWST is a multinational effort, spanning over 25 years of push and pull. 10 billion dollars later, we had the moment we witnessed on Dec 25^th!

Successful launch was only the beginning of the complicated mission. It has 341 points of failure in its next journey of around six months and anything can still go wrong! The telescope is now hurtling through the space to its designated point, the Lagrange point (L2), about 1.5 million kms away from earth. At L2, the gravity of earth and the Sun is balanced out and will eventually dock in its position about 28 days from the launch. It wont be until summer though, that the first pictures from JWST will be received.

So whats different in James Webb compared to Hubble?

1. Size. Hubble’s mirror size is approx 8 feet, whereas JWST mirror is about 21 feet in diameter. Hubble is the size of a bus, JWST is the size of a tennis court!.
2. The light itself that JWST will see will be different from Hubble. Hubble uses visible light – so it will see what we see, if we were in space at that location! JWST is only going to see the orange/red that we see and then infrared light beyond the red. The idea is to peep deeper into the space and it turns out that the deeper you peep, the more ‘red-shifted’ the light becomes. Stated alternately, what we see as normal visible light emitted billions of years ago now appears in infrared.
3. Hubble is orbiting the Earth. JWST will be orbiting the Sun. The infrared instruments on JWST need to be maintained at a very cold temperature (-266 deg C). The Lagrange point L2 offers conditions to achieve this. In fact the sun shields of JWST are so powerful that it can hide all of solar power and only let 1W be generated

As a fun fact, it is said that the JWST is so powerful that it can detect heat changes in fluttering of bees from a distance of 500,000 kms! That’s almost the distance between the Earth and the Moon!

How JWST moved out of sight of humanity?

I will summarize a rather elaborate process of how JWST detached from the Ariane5 upper stage and continued its journey – alone in the vast expanse of the universe – only to bring us more data to ascertain our theories or hypothesize new ones.

First, the moment the JWST detached from the upper stage of the Ariane5 launcher. This was the moment, 27 minutes after the launch that set JWST free!

Then, the rather spectacular views of the JWST from atop the upper stage as JWST drifts away into the space. Fig (b) shows the JWST back side view after detachment. Fig (c) shows the solar panels being unfurled through a carefully maneuvered time critical operation. This was critical for the JWST to start receiving the power and not become a piece of debris!

The solar panels were fully lit up by the solar rays – thereby signaling that all went well so far and the solar power was being used to charge the electronics on board!

The final view by humanity of the litup JWST as it hurtles away into the space towards its designated Lagrange point (L2). After this, we will never see the JWST again! We will see the images captured by it over next 5-10 years, but never the telescope itself!

As the final images like the one in fig (e) were being flashed, I was comprehending the magnitude of the moment. This was a picture for posterity. So many philosophical essays or science fictions can be written just around this moment of time! Many artists will come forth with their art forms to capture this moment. This moment has changed human quest for understanding of universe. To those who stare at night sky (Bangalore clouds willing :), do have these thoughts that eventually cross their minds at some time – just where does this infinite begin and where does it end? And the methodical answers to such questions so far agree with the big bang. We will know soon from the pictures of JWST, what were the earliest galaxies like? What were they composed of etc. I said its proverbial “Back to the Future 3” because it will really start detecting the faintest of signals that may have originated close to the time Big Bang occurred, or when the universe just came into being. These are fascinating times for the scientific pursuit and we all look forward to the treasure trove that JWST will share with us!

Finally, what new science can we expect? 

NASA, ESA and Canada spent around 10 billion dollars for a few top-level goals

1. To study light from the first stars and galaxies after the Big Bang.

2. To study the formation and evolution of these galaxies.

3. To understand the formation of stars and planetary systems.

4. To study planetary systems and origin of life!

As Ken Sembach, Director of the space telescope at Science Institute in Baltimore said, “Science wont be the same after today. Webb is more than a telescope – it is a gift to everyone who contemplates the vastness of the universe”. And gift it is. Hopefully, by the time of refleXion’s next issue, the JWST will be in L2 and an issue further later, we would have the first pictures.