James Webb Space Telescope


If you’ve followed the newsletter from the early days, you’re well familiar with the Hubble Telescope and its myriad astronomical contributions. Some of the most resplendent images of the universe have come from the famed telescope. One might argue all of the most gorgeous imagery of the cosmos to date has come from the mirror and lens of Hubble, including the eponymous Deep Fields.

In a time where space launches have become nearly common, some missions still stand out, some technologies still seem to be paradigm shifters. We might assert that Hubble is the most important mission since the Apollo programs, perhaps more monumental than the space shuttles, the International Space Station, and all the probes. Yet, as we learned in our exploration of Hubble in that early period of the newsletter, the telescope was almost a complete bust. The first years of operation were marred by faulty equipment, but spacewalks solved the problem.

Today, we have a candidate for the most important mission since Hubble. And recalling Hubble’s past is an important piece of the new puzzle, as we’ll see later in the article. On Christmas Day, the world launched the James Webb Space Telescope. The successor to the Hubble should be a revolutionary element to the study of the universe.

The Pillars of Creation, one of Hubble's most famous images - NASA

You might recall from science classes that visible light is just one part of the electromagnetic spectrum. From gamma rays to radio waves, they are all light, differing by wavelength and frequency. Scientists designed Hubble to detect electromagnetism between near ultraviolet and near infrared, with visible light smack in the middle. While Hubble was and is fantastic at “seeing” those frequencies, its design keeps it from showing us other bands. One part of the spectrum that really excites astronomers is the infrared band. As light moves through the universe, it undergoes a redshift. Essentially, its frequency lowers and it loses some energy. To see older and older forms of light, a telescope must, therefore, be able to see farther into the infrared portions of the spectrum. The James Webb Space Telescope will be able to do exactly that!

The process isn’t as simple as just tweaking a few knobs, however. For a telescope to see infrared light sufficiently, it must be kept cold. Really cold. Any form of heat would create too much noise to decipher. As you are well aware, a giant furnace sits at the center of our system. The sun makes it very hard to keep telescopes cold. Two options exist to solve the problem. Use an active coolant or come up with a design workaround. Coolant is effective but expensive and limited in terms of lifespan.

Still, the scientific boon from studying infrared light would be immense. In the early years of Hubble’s deployment, engineers started dreaming of the next generation. By 1996, early designs for the James Webb floated around NASA. With a Christmas 2021 launch, you can deduce the Webb enigma was not solved easily. Decades of problems, delays, and funding issues dogged the project. But with the ultimate solution, it’s easy to see why it took so long. We needed to get this sucker exactly right.

The top of the James Webb Space Telescope - NASA
The bottom of the James Webb Space Telescope - NASA

Beyond the extraordinarily elegant and aesthetically pleasing honeycomb design of Webb’s mirror, two things stand out.

First, we decided to forego coolant. Instead, scientists developed sunshields and radiators to keep the telescope cold. The sheets you see in the photos above comprise the sunshield. Fantastically, each layer is as thin as human hair! The magic of the elements (aluminum and silicon, specifically) allows something so minuscule to reflect sunshine away from the scope’s innards. Other portions of the craft are designed to radiate any other heat caused by computers or galactic electromagnetism.

The slightness of the sunshields hints at the second wonderful aspect of the telescope. In order for the non-coolant method to work, we actually have to send the telescope to a special spot in the solar system. The shields can’t constantly shift with the sun, so we’re blasting Webb off to a spot called a Lagrange Point (more on these in a future article!). At this spot, the telescope will find itself in equilibrium between the sun’s gravity and Earth’s pull. A benefit of such a spot is the telescope will remain approximately the same distance from our planet at all times while allowing it to stay constantly oriented in the same way toward the sun. So, the heat shield can face our star all the time!

Problem solved. Except for one small detail. That spot is about a million miles away.

The mirror on the James Webb telescope is 21 feet in diameter, significantly larger than Hubble’s 8-foot mirror. Webb’s light-collecting area is 5.6 times greater than Hubble’s. Yet, the new craft’s mass is just half of that of its predecessor!

The design of Webb brilliantly balances the need to have a bigger mirror and the need to have a bigger mirror that we can deploy a million miles away. 18 hexagonal mirrors form an interlocking Voltron mirror. The aforementioned hair-breadth heat shields cut down on weight. These designs still needed to fit inside existing rocket technology.

Folding to the rescue!

Deftly, engineers programmed Webb to unfold as it hurtles through space. Small components become a behemoth. This design contributed to some of the delays over the years, however. With delicate, tiny parts, something was bound to break or tear during testing. The heat shields ripped in 2018.

And there lies the rub when it comes to the James Webb Space Telescope. The Hubble resides just 340 miles above the Earth’s surface. When it malfunctioned, NASA sent astronauts to fix the issue. The Webb telescope will probe the oldest secrets of the infrared universe from a spot a million miles away. Sending humans to correct a crisis is, most likely, not possible. We needed to get it right, so spending more than two decades developing the craft seems wise.

NASA described the launch from French Guiana as “flawless.” With any luck, we’ll soon have images of the formation of the first galaxies. Without luck, we’ll have a very expensive hunk of sunshield wandering the solar system. This telescope is a big deal, a new paradigm for understanding the cosmos. Long live the JWST!

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3 thoughts on “James Webb Space Telescope”

  1. Pingback: Lagrange Points – themountainsarecalling.earth

  2. Pingback: A Big Week for Astrophotography – themountainsarecalling.earth

  3. Pingback: Webb’s First Lightshow – themountainsarecalling.earth

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