Figure 1: The initial image of HD 84406, a star in the constellation Ursa Major (the Great Bear), created by the James Webb Space Telescope. The misalignment of the mirrors capturing the light causes there to be multiple bright dots.
Source Credit: NASA JWST Flickr (LINK)
Last Christmas, the world saw the launching of the James Webb Space Telescope. In the following weeks, the media exploded with news and updates on Webb’s journey. After all, Webb is the most recent signature project for NASA following the Perseverance Mars rover project, which finally began to navigate through the barren landscapes of Mars’s Jezero Crater. Once again, NASA has surprised the world with its astounding level of technological advancement, so here we give a brief overview of the Webb and how its various parts work.
Webb is an infrared space telescope (say what?). As the name suggests, Webb is a telescope designed to operate in outer space, specifically for the purpose of capturing and analyzing infrared light. For the sake of structural coherence, we postpone our discussion about infrared light and consider the name “James Webb” first.
The James Webb Space Telescope is named after (you guessed it) James Edwin Webb, who served as the second-ever administrator of NASA during the 1960s in the midst of the cold war. Due to the political tensions between the United States and the Soviet Union, the two nations initiated a “Space Race”, a collective mission to have superior spaceflight technology. In the case of the United States, this was going to be achieved by sending a man to walk on the Moon's surface for the first time in history. Hence, during its early days, NASA focused on its manned spaceflight mission, Apollo. James E. Webb, knowing this would hinder the future proliferation of the now-dominant space program, took many risks to invest not only in the Apollo program, but also in the Mariner program and the Pioneer program – both programs studied nearby planets and solar weather.
In addition to the story behind the telescope’s name, what deserves the real spotlight is the innovative technology involved in the construction of this beast. Generally speaking, Webb consists of four parts: the Spacecraft Bus, the Optical Telescope Element (OTE), the Sunshield, and the Integrated Science Instrument Module (ISIM).
Figure 2: The properly aligned image of HD 84406, created by the James Webb Space Telescope. Upon alignment, the telescope will subsequently stack each dot on top of each other to form a single image. Source Credit: NASA JWST Flickr (LINK)
The Spacecraft Bus is a conglomeration of functions that provide the foundation for the other three major sectors of Webb. Not only does it have panels to collect energy from sunlight, but it also controls the orientation of the observatory and maintains the orbit of the spacecraft. In addition, the Bus houses a cryogenic system to lower the observatory to operating temperatures and facilitates communication between Webb and the Operations Control Center on Earth.
The OTE consists of two parts—the iconic 18 hexagonal mirror segments which collect light and the backplane which holds the mirror segments in place. Each mirror segment is composed of beryllium, the fourth lightest element which boasts a very high rigidity and stability in fluctuating temperatures. Behind each mirror segment is a small device called an actuator, which controls the orientation of the segment, thus helping the mirror reflect light in the right direction. In fact, Figure 1 shows the very first photo taken by Webb. Throughout the next few weeks, Webb will align its mirror segments via actuators until the captured photo shows an orderly, hexagonal pattern and are subsequently stacked upon each other to form one coherent image.
Because the purpose of Webb is to analyze faint infrared light originating from very distant sources, it is necessary to eliminate any other sources of light. Unfortunately, the sun is a constant source of mostly visible light and heat (which in turn raises the temperature of the spacecraft and makes it emit infrared light of its own). This is where the tennis-court-sized Sunshield plays its role. Because the orbit of Webb keeps the spacecraft nearly in line with the Sun and the Earth, the carefully designed five-layer Sunshield can block out the light and heat from the Sun and Earth. By doing this, the cold side of Webb remains and operates at an unbelievably cold temperature of -223 degrees Celsius.
The ISIM consists of four separate infrared imaging devices along with a spectrometer, which splits light into its component wavelengths. By doing so, we can analyze which elements planets, stars, and their atmospheres are composed of. Furthermore, the data collected by the ISIM will have lasting effects in the field of cosmology. By using infrared imaging technology, Webb will be able to obtain information about light originating from distant and old objects, which has been stretched with the persistent expansion of the universe. This will allow cosmologists to see what exactly occurred during the early ages of our universe. Webb will also give us hints about the life cycles of stars: how exactly they are born from the midst of stellar nebulae to how they go out with a glorious bang to move onto their life as dwarf stars, neutron stars, or even black holes. Other open questions that Webb will answer is the exact formation process of galaxies and the presence of more habitable exoplanets, hence advancing the frontiers of our understanding of the universe.
Q&A:
Hannah: You mentioned that Webb will allow us to explore the early ages of our universe and life cycles of stars. How long does it usually take for Webb to take and analyze these images? Will we need to wait several years?
This often depends on what object is under study. If the celestial object is very far away, the telescope needs some time to collect the light coming from that object. The analysis of the images is also dependent on the nature of the study. For instance, if we were to study the material composition of planets or stars using infrared spectroscopy, we already have sample wavelengths for comparison, thus taking us a relatively short time.
Sally: What are some obstacles Webb faces in addition to other sources of light?
The light originating from the sun ever so slightly pushes Webb out of orbit because the photons of the light transfer little amounts of momentum to the spacecraft. Due to this phenomenon, Webb occasionally needs to use its propellers to adjust its orbit.
Wooseok: In what ways is the James Webb Space Telescope more developed and effective compared to its predecessor, the Hubble Space Telescope?
Webb is simply a major performance improvement from Hubble. Because it has a much larger mirror as compared to Hubble, it can collect much more light, thereby producing a better, more informative image. Webb is also an improvement from Hubble in the sense that it is able to capture lights of larger wavelengths, meaning it can capture infrared light from distant, old objects, stretched over time by the expansion of the universe.
Works Cited:
Fisher, A. (2022, February 3). Photons incoming: Webb team begins aligning the Telescope. NASA. Retrieved March 30, 2022, from https://blogs.nasa.gov/webb/2022/02/03/photons-incoming-webb-team-begins-aligning-the-telescope/
NASA. (n.d.). Spacecraft Bus Webb/NASA. NASA. Retrieved March 30, 2022, from https://jwst.nasa.gov/content/observatory/bus.html
NASA. (n.d.). Mirrors Webb/NASA. NASA. Retrieved March 30, 2022, from https://jwst.nasa.gov/content/observatory/ote/mirrors/index.html
NASA. (n.d.). Backplane Webb/NASA. NASA. Retrieved March 30, 2022, from https://jwst.nasa.gov/content/observatory/ote/backplane.html
About beryllium. BeST. (n.d.). Retrieved March 30, 2022, from https://www.beryllium.eu/about-beryllium#:~:text=The%20rigidity%20of%20beryllium%20is,any%20other%20metal%20or%20alloy.
NASA. (n.d.). The Sunshield Webb/NASA. NASA. Retrieved March 30, 2022, from https://jwst.nasa.gov/content/observatory/sunshield.html
NASA. (n.d.). Instruments and ISIM (Integrated Science Instrument Module) Webb/NASA. NASA. Retrieved March 30, 2022, from https://jwst.nasa.gov/content/observatory/instruments/index.html
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