James Webb Telescope
A time machine that will help answer the secrets of the universe
On December 25, 2021, NASA’s three-decade-long effort culminated in the much-awaited launch of its newest and most ambitious telescope yet: the James Webb Telescope. This 10 billion dollar project was first discussed in 1990 with the goal of helping us better understand our universe. More than 30 years later, despite several budgeting scares and revisions to its design, the final telescope has been successfully constructed. The James Webb Telescope, also known as the Webb telescope or JWT, is 100 times more powerful than its predecessor, the Hubble Space Telescope. Now in space, JWT has unparalleled advancements that could help answer some of the largest questions about how galaxies, planets, and life developed.
The telescope’s appearance is best known for its signature golden primary mirror and its impressive dimensions. Its 6.1-meter tall primary mirror is constructed by 18 hexagonal segments, each with a 1.32m diameter. Its sun shield, a region of the telescope which protects it from overheating, has 21m by 14m dimensions.
Even though it is much larger than Hubble, JWT is 131kg lighter. Due to their unique geometry, the primary mirror and sun shield are foldable. This allowed for easy transport aboard the Ariane-5 ship which was launched from French Guiana.
Many consider the JWT a time machine, and in some ways this is true. The Webb telescope is predicted to be able to see light from 13 billion years ago, which is a quarter of a billion years after the Big Bang. This is because light takes time to travel. In a vacuum such as space, light travels at 299,792,458 meters per second, and a light-year, how far light travels in a year, is 10 trillion kilometers long. Take the example of the Earth and moon: light takes about 1.3 seconds to travel from the moon to Earth, so we see the surface of the moon how it was 1.3 seconds ago. As a result, the farther objects are, the longer it takes for light to travel, and the further back in time we can see.
The telescope is made up of a myriad of tools. Its largest elements are the primary and secondary mirrors whose role is to gather light which will later be analyzed and studied: the more light collected, the more clear and precise the images will be.
When an object is moving away, the wavelength of all light in the electromagnetic spectrum from that object is stretched, and as a result “shifted” towards the red part of the spectrum; this phenomenon is called redshift. When an object is moving toward, the wavelength is shrunk, and as a result “shifted” towards the blue part of the spectrum; this phenomenon is called blueshift. Both are really closely related to the Doppler Effect.
In the case of the JWT, visible light coming towards it is reshifted into infrared light which is what the telescope ultimately collects. Collecting infrared light is advantageous because it can penetrate through dust clouds which are especially common around new-forming planets.
Once this light is collected, it is passed to the second mirror which reflects it into the scientific instruments. Eventually, it is focused on infrared detectors, where these light photons are transformed into a voltage. During this step, light is analyzed by tools that extract data from it.
The James Webb Telescope has four major tools:
The first is called the Near-Infrared Camera (NIRCam) and is the primary imager for short-range infrared waves (0.6 µm — 5 µm; “red to near-infrared”). It allows for imaging, limited spectrography, and coronagraphs which are especially important for exoplanet studies. Spectrography uses spectrographs which are instruments that spread light onto a spectrum to extract information about a given object. Meanwhile, coronagraphs help the telescope identify objects by blocking bright light sources that outshine them. It does so by placing black circles on top of bright objects.
The second tool, the Near-Infrared Spectrograph (NIRSpec), enhances the use of spectrography, by extracting information about the temperature, atmosphere, and chemical composition of the object of interest (0.6 µm — 5 µm; “red to near-infrared”). In order to gather this information about an object, the telescope has to be focused on it for more than 100 hours. In order to maximize efficiency, a shutter system is used once again to filter out irrelevant light.
The third tool is the Near-Infrared Imager and Slitless Spectrograph (NIRISS) which increases focus on especially bright objects (0.6 µm — 5 µm; “red to near-infrared”). It is housed combined with the Fine Guidance Sensor which is responsible for keeping the telescope stable.
Lastly, the fourth tool is the Mid-Infrared Instrument (MIRI) which works with local infrared waves (4.9 µm — 28.8 µm). This means that it can penetrate very close dust clouds. In order for this system to function, it has an ideal temperature of 6.7 Kelvin, which is why the internal cooling system is crucial.
So… Where Is The Webb Telescope Now?
After its long and strenuous development, millions of scientists and enthusiasts are excited to see JWT at work. However, the telescope is not able to make use of these exciting advancements just yet.
It will spend half of its first year in space finishing its travels and calibrating its equipment. While the Hubble telescope lies 340 miles away from Earth, JWT will travel nearly 1 million miles away from earth to a location called the Lagrange Point 2 or L2; this location is one of five places in our solar system where the “the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them”; this means that the object is able to stay put. At the same time, it is an optimal location to limit the radiation that streams in from the sun and moon which could possibly skew data.
Two weeks after its launch, the Webb telescope is set to unfold. About one month after its launch, the telescope is set to reach L2. From that point on, the telescope will calibrate itself and slightly adjust the placement of its hexagonal segments to improve focus. Once this has occurred, the Webb is ready to take its first pictures.
As of January 24, 2022, Webb has reached L2.
After calibration, the telescope will spend its time learning about galaxies, exoplanets, stellar astrophysics, and our solar system. Over a year ago, NASA announced General Observer opportunities where scientists can investigate targets using Webb’s technology in its first year in orbit in addition to NASA’s plans. More than 1000 proposals were sent in by scientists from over 44 countries, and 286 proposals have been selected which will dictate Webb’s activity.
Within the next few months, we hope to see Webb prepare to begin its work, and we can’t wait!
Key Takeaways:
- The James Webb Telescope (often referred to as the Webb telescope, or JWT )is finally here!
- JTW could potentially look back 13 billion years ago.
- Due to a phenomenon called redshift, visible light coming from objects will be transferred to infrared light which will be absorbed by the telescope.
- The Webb has 4 major tools: Near-Infrared Camera, Near-Infrared Spectrograph, Near-Infrared Imager and Slitless Spectrograph, and Mid-Infrared Instrument. Several tools use coronagraphs and spectrographs.
- Once the telescope is launched, it will travel 1 million miles to reach Lagrange Point 2 where it will calibrate before beginning to image.
- As of January 24, 2022, the telescope has reached its destination and is now calibrating.
*references embedded in the text*
On a Personal Note:
In the words of Nelson Mandela, “Education is the most powerful weapon which you can use to change the world.” So thank you for reading my article and helping spread a bit of knowledge at a time.
If you enjoyed this article, feel free to like it, or view more of the content from my Medium page.
If you are a space enthusiast like me and are hoping to learn more about the JWT’s journey, you can find some resources, here, here, here, here, (and one more) here.