Step by Step
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Launch and orbit
JWST launched on December 25, 2021, and operates from the L2 Lagrange point, about 1.5 million km from Earth — a stable location that keeps the telescope consistently shaded from the Sun.
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The mirror and wavelength range
JWST's primary mirror is 6.5 meters across (compared to Hubble's 2.4 meters), made of gold-coated beryllium and composed of 18 hexagonal segments. It observes in near- to mid-infrared wavelengths, allowing it to see through dust and detect highly redshifted, extremely distant galaxies.
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First images and science highlights
JWST's first images were released in July 2022, providing the deepest infrared view of the universe ever captured, including galaxy clusters and nebulae in unprecedented detail. Science highlights include detecting galaxies at redshift z>10 (corresponding to just 500 million years after the Big Bang) and detecting CO₂ in the atmosphere of the exoplanet WASP-39b.
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Cost and development
JWST cost approximately $10 billion and took roughly 20 years to develop, reflecting the immense technical challenges of building and successfully deploying such a large, precise instrument in space.
Applied Walkthrough
1
Launched on Christmas Day 2021, JWST settled into its stable orbit at the L2 Lagrange point, about 1.5 million km from Earth, where it remains consistently shaded from the Sun's heat and light.
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Its enormous 6.5-meter mirror — nearly three times the diameter of Hubble's — combined with its infrared-focused instruments, allows it to peer through obscuring dust and detect extremely distant, highly redshifted galaxies that optical telescopes like Hubble simply can't see.
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When JWST's first science images were released in July 2022, they revealed the deepest infrared view of the universe ever captured — and subsequent observations have detected galaxies at redshift greater than 10, corresponding to just 500 million years after the Big Bang.
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Beyond peering into the deep past, JWST has also made major contributions to exoplanet science, detecting CO₂ directly in the atmosphere of the exoplanet WASP-39b — a landmark demonstration of its atmospheric characterization capabilities, achieved after roughly 20 years of development and about $10 billion in cost.
Exam Application
Exams test whether you know JWST's launch date and orbital location (L2), its mirror size and wavelength range compared to Hubble, and its major scientific achievements (early galaxy detection, exoplanet atmosphere characterization).
⚠ Common Trap
The most common trap is assuming JWST operates in the same wavelength range as Hubble — Hubble primarily observes UV, visible, and near-infrared light, while JWST is specifically optimized for near- to mid-infrared, which is precisely what allows it to see through dust and detect the most distant, highly redshifted galaxies.
✓ Quick Self-Check
1. When did JWST launch, and where does it orbit?
December 25, 2021; it orbits at the L2 Lagrange point, about 1.5 million km from Earth.
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2. How large is JWST's mirror, and how does it compare to Hubble's?
6.5 meters, compared to Hubble's 2.4 meters.
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3. What wavelength range does JWST primarily observe in, and why is this useful?
Near- to mid-infrared; this allows it to see through dust and detect highly redshifted, distant galaxies.
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4. What galaxy redshift has JWST detected, and what does this correspond to in cosmic time?
z>10, corresponding to about 500 million years after the Big Bang.
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5. What did JWST detect in the exoplanet WASP-39b's atmosphere?
CO₂.
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