UPSC Mains 2022 GS Paper 3 Q15: model answer
Launched on 25th December, 2021, James Webb Space Telescope has been much in the news since then. What are its unique features which make it superior to its predecessor Space Telescopes? What are the key goals of this mission? What potential benefits does it hold for the human race?
What the question wants
Explain JWST's unique features over earlier space telescopes, its key goals, and its potential benefits for humanity.
How to structure it
Features, goals, benefits.
- The mission
- Features that beat Hubble
- Goals
- Benefits
How to think it through
Launched 25 Dec 2021 on Ariane 5 from Kourou; NASA, ESA, CSA. 6.5 m segmented gold-coated beryllium mirror (18 hexagons) vs Hubble 2.4 m; infrared (0.6–28 micron) to see redshifted early galaxies and through dust; L2 orbit 1.5 million km; tennis-court five-layer sunshield keeps instruments below ~-223°C; instruments NIRCam, NIRSpec, MIRI, NIRISS/FGS. Goals: first galaxies after Big Bang, galaxy evolution, star and planet formation, exoplanet atmospheres (CO2 on WASP-39b 2022), origins of life. Benefits: knowledge, technology spin-offs (mirror tech, cryocoolers, eye surgery measurement), inspiration, international cooperation.
Model answer
Hubble showed us the universe in visible light. The James Webb Space Telescope (JWST), launched on 25 December 2021, looks at it in infrared, and that allows it to see things Hubble never could: the first galaxies, born when the universe was only a few hundred million years old.
Unique features
- Huge mirror: 6.5 metres across, made of 18 gold-coated hexagonal segments, against Hubble's 2.4 metres.
- Infrared vision: light from the earliest galaxies is stretched into infrared by the expansion of the universe; infrared also passes through dust clouds where stars are born.
- Sunshield the size of a tennis court, with five layers, keeping instruments at about minus 230°C.
- Orbit at L2, about 1.5 million km from Earth, where the Sun, Earth and Moon stay on one side.
- Instruments: NIRCam, NIRSpec, MIRI and NIRISS for imaging and spectroscopy.
- Folded launch: the whole telescope unfolded in space, a feat of engineering.
- A joint mission of NASA, ESA and the Canadian Space Agency.
Key goals
- See the first stars and galaxies after the Big Bang.
- Study how galaxies evolve.
- Watch stars and planetary systems being born.
- Read the atmospheres of exoplanets: in 2022 it detected carbon dioxide on WASP-39b.
- Search for conditions for life.
Benefits for humanity
- Knowledge of where we come from and whether we are alone.
- Technology spin-offs: precision mirror and measurement tools now used in eye surgery, and better detectors and cryocoolers.
- Cooperation: thousands of scientists from many countries share its data, including Indian astronomers.
- Inspiration for students to take up science.
- Better climate science methods from studying planetary atmospheres.
JWST does not just see further than Hubble; it sees further back in time, almost to the beginning.
Draw: A cross-section: mirror on top, five-layer sunshield below, Sun on the other side.
Keywords, cases and data to drop in
JWST, 25 Dec 2021, Ariane 5, 6.5 m mirror, 18 beryllium segments, infrared, redshift, L2, sunshield, NIRCam, NIRSpec, MIRI, WASP-39b CO2, NASA–ESA–CSA.
Where most answers lose marks
- Describing it as Hubble's replacement in visible light. Its key difference is infrared.
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Question text as printed in the official UPSC Civil Services (Main) question paper. The model answer is original Battle IAS work; use it to learn structure, not to memorise.
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