Right now, the telescope that will inspire the next generation is on the brink of unimaginable discovery.
The James Webb Space Telescope, named after NASA’s second administrator and nicknamed “Webb” or “JWST,” has scientists and space enthusiasts around the world brimming with anticipation. After twenty-five years of development, the world’s largest, most expensive, and most innovative telescope blasted off into space on December 25th, 2021, with a perfect launch.
Dr. Dan Coe, an astronomer with the Space Telescope Science Institute, is following each step of Webb’s journey as it travels to its final destination. Coe studies the first galaxies formed in the early universe and will lead two studies with the telescope. In the first study, his team will collect data on MACS0647-JD, the second most distant galaxy known. For the second study, he'll use Webb to look at the Sunrise Arc, one of the oldest, most highly magnified galaxies in the universe.
That magnification doesn’t come from the telescope itself. The magnification is from gravitational lensing, a phenomenon that occurs when massive clusters of galaxies have such a strong gravitational pull, they bend light from distant galaxies behind them. The images of distant galaxies are magnified and distorted as the light bends — like looking through a funhouse mirror.
Webb was designed to see the most distant galaxies and view the universe as it was billions of years ago. To understand the physics of seeing objects far away and in the distant past, we need to understand the physics of light.
How Does the Telescope Work?
As you probably know, light does not travel instantaneously.
There is a speed of light.
When a far away object emits light, it takes time for that light to reach us. We see that object as it was at the instant the light was emitted.
For example, the Sun is, on average, about 93 million miles away from Earth. Light from the Sun takes about eight minutes and twenty seconds to travel that distance. So if the Sun were to suddenly have sunspots that make a giant smiley face, we wouldn’t know about it for over eight minutes.
The farther out we look into space, the further back we look in time. The Andromeda Galaxy is one of our closest neighbors – about 2.5 million light-years away. When we look up at the Andromeda Galaxy, with or without a telescope, we see it as it existed 2.5 million years ago.
Bigger telescopes and darker skies allow us to see fainter celestial objects at greater distances. When the Webb Space Telescope looks out into space, it looks back to when the very first galaxies formed a billion years ago.
Webb is unlike any telescope ever built before. Not only is it the largest space telescope ever built, but it is so big that it had to be folded up in order to fit inside the Ariane 5 rocket. The mirror is made up of eighteen individual hexagonal-shaped mirrors. Together, these eighteen mirrors unfold and combine, like origami, to form a 6.5 meter mirror that is six times larger than the Hubble Space Telescope mirror.
A sunshield of five shiny layers protects the detectors at the center of the mirror from Sun and Earth radiation. This is very important because Webb doesn’t see visible light. Instead, Webb sees infrared light. Like night vision goggles, infrared light allows Webb to see objects that are otherwise invisible to telescopes like the Hubble Space Telescope.
The image above is two views of the Carina Nebula: one in visible light and one in infrared light. The visible light image shows the surface features of the beautiful interstellar dust cloud. The infrared image shows the many stars inside and behind the interstellar cloud.
Not only that, but infrared light shows us features and details within the cloud that were once invisible. For example, we can now see two white jets streaming in opposite directions near the center of the cloud. By studying these jets, astronomers and astrophysicists might better understand the process of star formation.
Where is the Telescope Going?
To see galaxies far away, Webb needs to be located in a cold, dark region of space. Coe explains: “We need infrared to study [distant] galaxies and to peer through dust, among other things. The biggest challenge is keeping everything cold enough so that the heat doesn't swamp out the faint infrared light we're observing. Hence the giant sunshield and going a million miles from Earth.”
The Sun, Earth, and moon all radiate infrared heat that would overload the sensors and essentially blind the telescope. Therefore, Webb is on its way to what astronomers call “L2,” which is the second Lagrange point in the Earth-Sun system.
L2 is the ideal placement for Webb. It’s close enough to communicate quickly with Earth and the telescope can be kept cool while its sunshield continuously blocks the radiation from the Sun, Earth, and Moon.
Webb will take a month to reach its orbit around L2. As the telescope travels through space, it is slowly and carefully unfolding itself. As of now, the most worrisome portion of the unfolding — the sunshield — was successfully and fully deployed. Webb is now protected from the largest heat sources in the solar system. Next will be the unfolding of the secondary and then primary mirrors.
The fascinating physics of Lagrange points, named for mathematician and astronomer Joseph-Luis Lagrange, are covered and calculated in Art of Problem Solving's PhysicsWOOT course.
When Can We Start to See New Images?
Scientists will take months to calibrate the telescope. According to Coe, we can expect to see the first stunning images from Webb after about six months.
That's not too long — we waited decades for the launch. Now, we only have to wait until the summer to start seeing the universe through new eyes. Coe says, “Hubble has inspired so many people to learn about their universe, create art, and pursue passions and careers in STEAM. JWST will inspire the next generation just like Hubble did.”
Above all, the James Webb Space Telescope is history in the making. Already, scientists and engineers are using the technology developed for Webb for other applications in optics, aerospace, and medical industries.
For Coe, the potential for future scientific discoveries are inspiring. “Like Hubble, JWST will give humanity a shared sense of wonder in our universe. We may be the pinnacle of creation, or there may be many more advanced lifeforms out there. Either way, the immensity of it all helps me put life's challenges into perspective and appreciate our planet and where we've come from.”