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When NASA unveiled the first full‑color images from the James Webb Space Telescope (JWST) in July 2022, even seasoned astronomers were struck by their beauty. One image—a stunning infrared view of the Carina Nebula, a star‑forming region 7,500 light‑years away—captured the imagination. “This is an art piece,” remarked René Doyon, a principal investigator on the JWST mission, at a NASA press conference.
JWST’s success builds on the legacy of the Hubble Space Telescope, launched in 1990. Hubble revolutionized our view of the universe, delivering deep‑field images of distant galaxies, spectacular supernovae, and nebulae, and helping to determine the universe’s age and expansion rate. Its iconic photographs are now embedded in textbooks, news headlines, and laptop wallpapers worldwide.
Rather than replace Hubble, JWST was designed to extend its reach. While Hubble observes visible and ultraviolet light, JWST specializes in infrared, allowing it to peer through cosmic dust and detect faint signals from the earliest galaxies. Together, they form a powerful duo: Hubble looks far; JWST looks deep.
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Hubble orbits Earth at about 320 miles, making it accessible for repairs—Hubble famously underwent a corrective optics upgrade after its initial blurry images. In contrast, JWST operates from the second Lagrange point (L2), roughly 1 million miles from Earth, where it can “hover” using the combined gravitational forces of the Sun and Earth. This distant position grants JWST an unobstructed view of the cosmos but also means that any repair would be impossible.
The most significant distinction between the two telescopes is their spectral range. Hubble captures ultraviolet, visible, and a narrow band of near‑infrared light (0.1–2.5 µm). JWST observes primarily in the infrared, spanning 0.6–28.5 µm. Because light stretches (redshifts) over vast distances, galaxies from the early universe emit light that has shifted into the infrared by the time it reaches us. Hubble could hint at these structures; JWST can resolve them in detail.
Both telescopes use curved mirrors instead of lenses, but their designs differ. Hubble employs a Ritchey‑Chrétien system—a deeper‑curved mirror set that yields high clarity across a wide field. JWST uses a three‑mirror anastigmat design, incorporating a third mirror that delivers unprecedented detail from the farthest reaches of space.
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Collaboration is essential, and Hubble and JWST exemplify complementary ambitions. Hubble’s 2.4‑meter primary mirror (≈ 8 ft) is dwarfed by JWST’s 6.5‑meter mirror (≈ 21 ft), enabling the latter to gather far fainter light from deeper in space and further back in time. JWST’s larger size also necessitates a sunshield the size of a tennis court to keep its instruments cold for infrared observations.
Hubble remains operational, often observing the same targets as JWST at different wavelengths. While Hubble’s near‑infrared capability is notable, its design favored shorter wavelengths. JWST’s broader infrared range makes it superior for studying exoplanets, cool brown dwarves, and galaxies up to nine times fainter than those detectable by Hubble.
Looking forward, the Nancy Grace Roman Space Telescope, slated for launch in 2027, will continue this lineage. Designed with a field of view 100 times greater than Hubble’s, it will help scientists probe dark energy, exoplanets, and planetary systems within our galaxy. These observatories represent the pinnacle of human ingenuity, engineering, and collaborative science. Even as many people cannot see the Milky Way with the naked eye, our species is rapidly gaining unprecedented access to the universe.
