Since the dawn of time, humanity has looked up at the sky to understand the cosmos and our place within it. Throughout history, we have designed increasingly sophisticated instruments to explore the stars—from the earliest optical telescopes to the most advanced space observatories. In this quest to unravel the universe’s mysteries, the James Webb Space Telescope (JWST) has marked a turning point.
Launched on December 25, 2021, this technological colossus is the most powerful and complex telescope ever built (1). With a 6.5-meter primary mirror and unprecedented infrared observation capabilities, Webb has allowed us to see the cosmos like never before. From the oldest galaxies to the atmospheres of distant exoplanets, its discoveries are redefining our understanding of the universe.
In this article, we will review its historical background, the technological innovations that make it unique, and some of its most striking images and findings.
Historical Overview
The first ideas for JWST emerged in 1989, as part of the search for a successor to the Hubble Space Telescope (HST). The HST, launched in April 1990, is a telescope that captures visible light and enabled the analysis of planetary atmospheres orbiting other stars and the discovery of dark energy (2). The concept of developing a passively cooled infrared telescope arose in 1996, with the goal of observing the early universe by capturing infrared light and surpassing the limitations of the HST. This technology would allow detection of distant galaxies whose light—stretched to longer wavelengths by the universe’s expansion (a phenomenon known as redshift)—was inaccessible to Hubble’s optical instruments (3).
Fig 1. Hubble Space Telescopa orbiting the Earth.
The project entered its design and planning phase between 1997 and 2002, during which it received its official name: James Webb Space Telescope, in honor of NASA’s administrator during the Apollo program. From 2003 to 2011, construction progressed, but in 2012, it faced critical delays due to the complexity of assembling its components and conducting rigorous testing.
In 2019, after successfully passing all technical evaluations, final preparations for launch began. This became a reality in December 2021, when an Ariane 5 rocket lifted it off from the Kourou spaceport in French Guiana. However, the challenge continued: over the next seven months, the telescope was positioned and deployed in space using 140 interdependent mechanisms—where a single failure could have compromised the entire mission.
Fortunately, thanks to the demanding work of everyone involved, JWST was a complete success and has been active and sending back images for over two years.
From the beginning, JWST (originally called the “Next Generation Space Telescope”) was conceived as an international project, led by NASA with support from the Canadian and European Space Agencies (CSA and ESA), and in collaboration with institutions from over twenty countries. This global alliance, however, faced unprecedented challenges: the telescope took 25 years to materialize, at a cost of $10 billion, involving more than 10,000 people. With these ambitious goals came a few challenges:
Technological Innovation
The JWST is composed of four major components: the Optical Telescope Element (OTE), the Integrated Science Instrument Module (ISIM), the sunshield, and the spacecraft bus (4).
Fig 2. Components of the James Webb Space Telescope.
Since JWST is an infrared telescope, interference from visible light and temperature management were critical factors. To efficiently capture infrared light (emitted by cold and distant objects), the ISIM sensors had to operate at temperatures near -267°C—just 6°C above absolute zero. To achieve this, a sunshield had to be developed.
The sunshield consists of five layers of Kapton, a lightweight and flexible material coated with aluminum and doped silicon. These five layers can insulate temperatures ranging from 85°C down to the -267°C required for operation. Each layer is the size of a tennis court (21 x 14 meters) and as thin as a human hair. This passive cooling system eliminated the need for chemical coolants, simplifying long-term operation (5).
Fig 3. Parasol fully deployed.
The sunshield is impressive, but the most eye-catching feature of the JWST is undoubtedly its golden primary mirror, made up of eighteen hexagonal segments. However, these dazzling panels posed a major challenge for their developers. First, because of the extremely low operating temperatures, the team had to find a lightweight material with high thermal stability—meaning it would retain its shape when exposed to cryogenic temperatures like those in space. The material chosen was beryllium.
Next, an ultra-thin layer of pure gold had to be added to the polished beryllium to enhance its infrared reflectivity. This process was repeated for the secondary mirror, tertiary mirror, and fine steering mirror.
Finally, each mirror segment had to be aligned with nanometer precision (a billionth of a meter). To achieve this, each panel was equipped with seven motors that could be remotely adjusted from Earth.
The result was a 6.5-meter-wide primary mirror—nearly three times larger than Hubble’s, but one hundred times more powerful (6).
Fig 4. Mirrors of the James Webb Space Telescope.
Continuing with the ISIM, this module houses the heart of James Webb:
- Near Infrared Camera (NIRCam)
- Near Infrared Spectrograph (NIRSpec)
- Mid-Infrared Instrument (MIRI)
Fig 5. ISIM Assembly.
Star- and planet-forming regions are invisible to optical telescopes like Hubble because they are enshrouded in dense clouds of cosmic dust. However, the infrared light detected by MIRI penetrates these barriers, revealing processes such as the formation of protoplanetary disks or collisions between young galaxies.
Beyond the dust, JWST also captures light from the first galaxies, whose original emissions (in ultraviolet or visible light) have been stretched into the infrared by the expansion of the universe—a phenomenon known as redshift. This is where NIRCam comes into play, designed to detect structures that existed more than 13.5 billion years ago, offering a glimpse of the cosmos in its infancy.
By analyzing with NIRSpec the infrared light that passes through the atmospheres of distant planets, JWST can identify molecules like water, carbon dioxide, and methane—key to searching for habitable conditions. These data, impossible to obtain with conventional telescopes, are crucial clues in the search for Earth-like worlds (7).
Lastly, there is the spacecraft bus. This part carries the subsystems necessary for the overall operation of the observatory: electrical power, attitude control, communications, command and data handling, propulsion, and thermal control (8).
Fig 6. Spacecraft bus assembly.
So far, we have covered JWST’s main components and dimensions. But how do you launch it into space when its size exceeds that of any existing rocket? The answer: make the primary mirror and sunshield foldable (8).
Fig 7 Parasol del Telescopio Espacial James Webb siendo empacado.
One of JWST’s greatest challenges was its deployment in space. Unlike Hubble, which orbits Earth and could be serviced by astronauts, JWST is located at Lagrange Point L2—1.5 million kilometers from our planet—where no crewed mission can reach. To get there, an Ariane 5 rocket—the largest available at the time—was used.
The deployment involved enormous mechanical complexity. Every mechanism had to be thoroughly evaluated on Earth under simulated space conditions—hence the many years of delay.
Fig 8. Illustration of JWST leaving orbit.
To see James Webb’s location in the solar system, visit: https://eyes.nasa.gov/apps/solar-system/#/sc_jwst?embed=true
Highlight Discoveries
Here is a selection of groundbreaking discoveries that highlight the power and reach of the James Webb Space Telescope:
- The Oldest Galaxy
JADES-GS-z14-0, discovered by the JADES team, is a record-breaking galaxy that emerged just three hundred million years after the Big Bang. With an extreme redshift of fifteen, its light has been stretched fifteen times from its original emission into the infrared, allowing JWST to reveal a surprisingly large and luminous structure for its time—fueled by intense young star formation. This discovery, which challenges previous expectations about early galaxy evolution, is supported by ultra-deep images and spectroscopy that detected unusual hydrogen and oxygen emissions, marking JADES-GS-z14-0 as a revealing archetype of the early universe. This galaxy lies a staggering 13.4 billion light-years away (9).
Fig 9. Infrared image of the JADES-GS-z14-0 sector.
- A Very Hungry Black Hole
Astronomers discovered a low-mass supermassive black hole, LID-568, in a dwarf galaxy in the early universe—just 1.5 billion years after the Big Bang. Using data from both Webb and the Chandra observatory, they determined it is consuming matter at a rate forty times higher than the theoretical limit, explaining how such objects evolve so rapidly. Its detection in the COSMOS catalog suggests that black holes can gain much of their mass during brief episodes of extreme accretion. This finding is challenging previous theories about their formation (10).
Fig 10. Artist’s concept of LID-568.
- A Perfect Einstein Ring
JWST has captured an almost perfect Einstein Ring—a gravitational lensing phenomenon where light from a distant galaxy bends around a closer one due to its intense gravity, forming an almost flawless ring. This effect, predicted by Einstein, not only provides a magnified image of distant galaxies but also allows scientists to study the distribution of dark matter, which influences how the light is distorted. By analyzing these rings, astronomers can precisely measure the mass of galaxies and delve deeper into the evolution of the early universe. This object is located approximately 21,500 light-years away (11).
Fig 11. Image of the complete Einstein Ring JWST-ER1.
Fig 12. Some examples of incomplete Einstein Rings.
- Galactic Collision
The collision of two galaxies—an elliptical and a spiral—was captured by JWST in September 2024. Known together as Arp 107, they form a smiling face in the sky, with two bright “eyes” and a wide “smile.” In this interaction, the spiral galaxy has been distorted by the collision, resembling the Cartwheel Galaxy. However, due to a less direct collision, only the spiral arms were significantly affected. Using its superior resolution through MIRI and NIRCam, Webb reveals how galactic interactions can compress gas, triggering star formation, although they can also scatter material, potentially limiting further star creation. Arp 107 is in the process of merging—a transformation that will take hundreds of millions of years—and while it will eventually lose its “smile,” it will evolve into an equally fascinating structure for future astronomers. It lies approximately 465 million light-years from Earth, in the constellation Leo Minor (12).
Fig 13. Arp 107 Galaxy Collision.
- Exoplanet with Water in Its Atmosphere
A groundbreaking JWST discovery in the field of exoplanets revealed the presence of carbon-bearing molecules—such as methane and carbon dioxide—in the atmosphere of K2-18 b, a planet 8.6 times more massive than Earth that orbits within the habitable zone of the red dwarf K2-18, located 120 light-years away in the constellation Leo. These findings support the hypothesis that K2-18 b could be a Hycean exoplanet, a planet with a hydrogen-rich atmosphere and a surface covered in water oceans. Additionally, the possible detection of dimethyl sulfide (a molecule associated with marine biological activity on Earth) suggests potentially life-friendly conditions and expands our understanding of the diversity and habitability potential of sub-Neptune planets (13).
Fig 14. Official artist’s concept of exoplanet K12-18 b
To explore over 60 mind-blowing Webb discoveries, check out this video: https://www.youtube.com/watch?v=1Ul2tR7qxqM&t=229s
Conclusion
These recent discoveries remind us of how vast and mysterious the universe truly is, and how each new exploration brings us closer to understanding it. Such breakthroughs are made possible by the tireless efforts of multidisciplinary teams of scientists, engineers, and experts from around the globe, working together to unravel the mysteries of the cosmos. Their dedication and collective effort allow us to expand the frontiers of human knowledge.
References
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3. Gardner, J. P., Mather, J. C., Clampin, M., Doyon, R., Greenhouse, M. A., Hammel, H. B., … Stiavelli, M. (2006). The James Webb Space Telescope. Space Science Reviews, 123(4), 485–606.
4. NASA. (s.f.). Webb Observatory - NASA Science. Recuperado de science.nasa.gov sitio web
5. NASA. (2024b, Agosto 12). Webb’s Sunshield - NASA Science. Recuperado de Nasa.gov sitio web
6. NASA. (2024c, Agosto 12). Webb’s Mirrors - NASA Science. Recuperado de Nasa.gov sitio web
7. NASA. (2024d, August 12). Integrated Science Instrument Module (ISIM) - NASA Science. Recuperado de Nasa.gov sitio web
8. NASA. (2024e, Enero 4). Webb y Origami. Recuperado de NASA Science sitio web
9. Carniani, S. (2024, Mayo 30). Earliest, most distant galaxy discovered with James Webb Space Telescope. Recuperado de University of Cambridge sitio web
10. Mohon, L. (2024, Noviembre 13). Astronomers Find Early Fast-Feeding Black Hole Using NASA Telescopes - NASA. Recuperado de Nasa.gov
11. Baker, H. (2023, Septiembre 29). “Einstein ring” snapped by James Webb Space Telescope is most distant gravitationally lensed object ever seen. Recuperado de Space.com sitio web
12. NASA Webb Mission Team. (2024, Septiemre 18). NASA’s Webb Provides Another Look Into Galactic Collisions - NASA Science. Recuperado de science.nasa.gov
13. NASA. (2023). Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18 b - NASA. Recuperado de Nasa.gov
