🗞️ Why in News: Scientists using NASA’s James Webb Space Telescope (JWST) detected methane in the chemical fingerprint of interstellar comet 3I/ATLAS — the first direct methane detection in any interstellar object and the first peek at the chemical composition of material from another star system. The findings were published in The Astrophysical Journal Letters.
3I/ATLAS — The Object
| Parameter | Detail |
|---|---|
| Designation | 3I/ATLAS (“I” = interstellar) |
| Discovery | Discovered in July 2025 — by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Chile |
| Type | Confirmed interstellar object passing through our solar system |
| Status | By early 2026: beyond Jupiter’s orbit, exiting the solar system |
| Significance | Only the 3rd confirmed interstellar object in history |
The Three Interstellar Visitors
| Object | Year | Type | Key Feature |
|---|---|---|---|
| 1I/'Oumuamua | 2017 | Unusual (possibly flat slab or hydrogen iceberg) | No outgassing detected; non-gravitational acceleration |
| 2I/Borisov | 2019 | Comet | First interstellar comet; CO/H₂O detected |
| 3I/ATLAS | 2025-26 | Comet | Methane detected by JWST — first in any interstellar object |
The Detection — JWST MIRI
- Instrument: Mid-InfRared Instrument (MIRI) on JWST.
- Method: Spectroscopy — analysing the wavelengths of light absorbed or emitted by the comet as it was heated by the Sun. Different molecules have unique spectral “fingerprints.”
- What was found: Methane (CH₄) — a key organic molecule; also implies the presence of other volatile ices.
- Observations: Conducted during late 2025 (two sessions as the comet headed out at ~205 and ~236 million miles from the Sun) — results announced June 2026.
Why Methane on an Interstellar Object Matters
- Chemical record of another star system — The comet formed around a different star billions of years ago; its composition reflects the chemical conditions of that planetary system.
- Volatile inventory — Methane is a highly volatile “supervolatile” (boils off at very low temperatures); its presence suggests the comet was stored in a very cold environment (in a distant Oort-Cloud-like reservoir around another star) before being ejected.
- Building blocks of life — Methane + CO₂ + H₂O are key molecular building blocks; detecting them in an interstellar visitor provides data on the universality of organic chemistry in the cosmos.
- Planetary formation — The chemical mix of 3I/ATLAS tells us about the outer solar nebula of its parent star — widening our understanding of how planetary systems form.
About JWST
| Feature | Detail |
|---|---|
| Launch | Launched in December 2021 |
| Orbit | L2 Lagrange point (~1.5 million km from Earth, on the Sun-Earth line) |
| Mirror | 6.5 m primary (segmented beryllium+gold mirrors) |
| Speciality | Infrared observation — can see through dust; observe earliest galaxies; detect atmospheric signatures of exoplanets |
| Partners | NASA, ESA, CSA |
India & Space Science Context
- JWST complements India’s own deep-space ambitions: Aditya-L1 (solar observation, L1 point, 2023), Chandrayaan-3 (lunar south pole, 2023), and planned Shukrayaan (Venus orbiter).
- India is not a partner in JWST but uses public JWST data for research through IIA (Indian Institute of Astrophysics), IUCAA, and TIFR.
UPSC Relevance
| Paper | Relevance |
|---|---|
| GS3 | Science & Tech — JWST, interstellar objects, spectroscopy, comets, planetary science |
| Prelims | 3I/ATLAS (3rd interstellar object); 1I/'Oumuamua (2017), 2I/Borisov (2019); JWST (launched in Dec 2021; L2 orbit; NASA+ESA+CSA); MIRI instrument; methane (CH₄) |
Facts Corner
📌 Facts Corner — Knowledgepedia
3I/ATLAS:
- Only the 3rd confirmed interstellar object in history
- Discovered in July 2025 by ATLAS telescope (NASA-funded), Chile
- JWST MIRI detected methane — first methane detection in any interstellar object
- Published: Astrophysical Journal Letters
Interstellar objects history:
- 1I/'Oumuamua (2017) — unusual; no outgassing; non-gravitational acceleration
- 2I/Borisov (2019) — first interstellar comet; CO/H₂O detected
- 3I/ATLAS (2025-26) — methane detected by JWST
JWST: launched in December 2021; L2 Lagrange point; 6.5 m mirror; NASA+ESA+CSA; infrared observatory
Methane significance: Supervolatile; suggests cold origin; organic chemistry in another star system
Sources: NASA, Astrophysical Journal Letters
Source: JWST Detects Methane on Interstellar Comet 3I/ATLAS — First Chemical Fingerprint — Ujiyari.com | Free UPSC & State PCS Current Affairs
