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Answer: Webb is the largest and most powerful space observatory launched so far. It observes mainly in infrared light (0.6 to 28 micrometers), orbits the Sun about 1.5 million km from Earth near the second Lagrange point (L2), and can see light from the first galaxies, over 13.5 billion years ago.

Design highlights

• Folding mirror: too big for its rocket, it folded origami-style and unfolded in space. Mirrors are beryllium, coated with about a golf ball's mass of gold.
• Sunshield: five layers block infrared heat from the Sun, Earth and Moon so the telescope stays cold.
• Instruments: NIRCam, NIRSpec, MIRI and a fourth guidance/slitless instrument.

Why infrared and why L2

Distant galaxies' light is stretched into the infrared, and Earth's atmosphere blocks much infrared. At L2 the Sun, Earth and Moon are all on one side, which the sunshield can block. Webb took about a month to get there. Hubble, by contrast, orbits close to Earth.

Webb vs Hubble

NASA says Webb's angular resolution in the near infrared matches Hubble's in visible light, but Webb sees deeper into the infrared.

Claims

• id: C1 claim: Webb is the largest and most powerful observatory ever sent to space. source: S1 evidence: "Webb is the largest and most powerful observatory ever sent to space"
• id: C2 claim: Webb has a 5-layer sunshield against infrared radiation. source: S1 evidence: "Webb has a 5-layer sunshield that protects the telescope from the infrared radiation of the"
• id: C3 claim: Webb can see back over 13.5 billion years. source: S1 evidence: "allows it to peer back in time over 13.5 billion years"
• id: C4 claim: Webb works from 0.6 to 28 micrometers. source: S2 evidence: "Webb works from 0.6 to 28 micrometers"
• id: C5 claim: Webb's angular resolution matches Hubble's, but in the near infrared. source: S2 evidence: "Webb's angular resolution, or sharpness of vision, is the same as Hubble's, but in the"

Sources

• [S1] James Webb Space Telescope. NASA. https://science.nasa.gov/mission/webb/ . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Webb FAQs. NASA. https://webb.nasa.gov/content/about/faqs/faq.html . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_pn27egdz,
  author = {{iinventedlight}},
  title = {{The James Webb Space Telescope: an infrared observatory}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/james-webb-space-telescope/},
  note = {Permanent ID iil:note:pn27egdz. License: CC-BY-4.0.},
}

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