It’s about time for the James Webb Space Telescope (JWST) to leave Earth and embark on its amazing mission to observe the infrared universe. I know a lot of folks are waiting anxiously for it to do so, myself included. If you go to the James Webb Space Telescope site, you will find a lot of material to check out about the instruments, the spacecraft, and the science that JWST can do.
In my last article, I wrote about the launch and the telescope, so today I want to focus on its mission. Essentially, it is to “uncover the hidden universe.” What does that mean?
The telescope and its instruments can “see” (detect) infrared light. Most of that light is in wavelengths we can’t see with our Mark I eyeballs. They limit our vision to a narrow part of the electromagnetic spectrum of light. There are things that occur in other wavelengths (such as ultraviolet or gamma or radio or infrared) that we’d never know about without specialized instruments such as JWST’s.
So, the “infrared universe” is out there, we just can’t see it that easily. At least, not without special instruments. Another thing about infrared (IR), is that Earth’s atmosphere interferes with the detection of that light. Sure, there are some infrared-enabled observatories on the planet, but they’re all at very high altitudes, where the atmospheric water vapor, for example, is quite low. The best place, really, to do infrared astronomy, is from space. And, the absolute best way to do it is to put the spacecraft well away from Earth, where the instruments can detect the light without any interference. And that’s what JWST can do.
What’s In the Infrared Universe
Just about everything in the universe has what you can think of as an “infrared signature.” That includes planets, asteroids, moons, worlds around other stars, the stars themselves, nebulae, and galaxies. It means that they all emit (or reflect) infrared light. That gives JWST a wide variety of objects and events to study, which makes it an exciting mission and a worthy partner to the Hubble Space Telescope (which is sensitive mostly to visible and some infrared and a little ultraviolet light).
Ancient Light and Modern Exploration
JWST explore the “current universe” and fill in some crucial information about objects and events “out there”. The telescope will be able to look far back in time as well as across space. That, for me, is one of the most interesting topics its observations will explore. It will help answer the question: “What happened in the earliest times in the universe?”
The chart here shows a timeline of the universe in very simple detail. It goes back to the very beginning of our universe, some 13.8 billion years ago. Now, we know the universe formed in an event called “The Big Bang.” It went through two phases. One was one called the Dark Ages when everything was… well… dark. That didn’t last very long, in the cosmic scheme of things, maybe about 200 million years. Then, the first stars were born and they began to shine.
This was a period called the “Epoch of Reionization.” It essentially means that things “lit up” again as the infant universe progressed. Those, early massive stars lived short, intense lives, and ended in spectacular supernova explosions. Their materials seeded the early universe with materials that ended up in clouds of gas and dust. Those were birthplaces for a second generation of stars. At around the same time, gravity began collecting these stars and nebulae into the first galaxies. The universe has continued to expand throughout its history. Along the way, more stars and galaxies have evolved to what we see today.
Observing that Infrared Universe
JWST is able to take advantage of a secret key to the ancient universe contained in infrared light. Light from those ancient events, stars, and galaxies, traveled across space for us to “see”. As it did, it was stretched by the expansion of the universe. So, those ancient stars may have emitted visible light, or near-infrared or even ultraviolet wavelengths. But, all that light got stretched well into the infrared part of the electromagnetic spectrum. Since JWST is very sensitive to the infrared spectrum, it’s going to act as a time machine. That will allow us to see what happened “way back when.” In essence, it’s going to probe the Epoch of Reionization and show us what those first stars and galaxies were like.
Stay Tuned
Currently, the JWST is scheduled for launch at 7:20 a.m. (Eastern Time) on December 24, 2021. If all goes well, it will ride to space aboard an Ariane 5 rocket from the ESA launch site in Kourou, French Guiana. You should be able to log into NASA TV or NASA Live to follow the launch and deployment activities. It’s going to be a great day for a launch, one that JWST scientists, technical staff, and launch are eager to see.