In a landmark discovery, scientists have used the James Webb Space Telescope (JWST) to detect five large, carbon-based molecules frozen in the icy envelope of a protostar beyond our own galaxy. The protostar, named ST6, is located in the Large Magellanic Cloud (LMC) — a small galaxy orbiting the Milky Way roughly 160,000 light-years away.
The molecules identified include methanol, acetaldehyde, ethanol, methyl formate, and remarkably acetic acid (the compound that gives vinegar its smell). Acetic acid had never before been conclusively found frozen in space.
What makes the finding especially exciting is the challenging environment of the LMC: it has a lower abundance of “heavy” elements (i.e., lower metallicity) and intense ultraviolet radiation — conditions thought to mirror those in the early Universe. And yet, despite these harsh conditions, complex organic chemistry appears to be taking place.
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How the Discovery Was Made
On March 10, 2024, JWST’s Mid-Infrared Instrument (MIRI) with the Medium Resolution Spectrograph (MRS) observed ST6 across wavelengths from 4.9 µm to 27.9 µm. The high spectral resolution and sensitivity allowed the team to detect absorption features of ices on dust grains around the protostar. These ices locked in complex organic molecules (COMs) on the surfaces of those grains.
Before this, only methanol had been securely detected in icy form around protostars — and only within our own Milky Way.
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What Was Found
Here’s a breakdown of the five complex organic molecules identified in the ice around ST6:
Methanol (CH₃OH) – Already known and expected, but once again confirmed in icy environments.
Acetaldehyde (CH₃CHO) – A molecule with a carbonyl and an aldehyde group, rarely found in solid state beyond our galaxy.
Ethanol (CH₃CH₂OH) – The same molecule found in alcoholic beverages, but here frozen in space around a forming star.
Methyl formate (HCOOCH₃) – A more complex molecule with an ester functional group.
Acetic acid (CH₃COOH) – The standout: never before conclusively detected as ice in space.
In addition, the spectrum of ST6 showed many “simple” ice constituents (water, CO₂, CH₄, etc.) and hints of a possible detection of glycolaldehyde (HOCH₂CHO) — a sugar-like precursor molecule — although that one remains tentative.
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Why It Matters
This discovery matters for several key reasons:
New frontier: It is the first time that so many large organic molecules have been detected frozen in the ice around a protostar outside the Milky Way.
Low-metallicity context: ST6 resides in an environment with only about one-third to one-half the metallicity of our galaxy. Metals (in astrophysical terms: elements heavier than helium) and dust grains are crucial for molecule formation and shielding from radiation. Finding complex organics despite fewer heavy elements suggests that pre-biotic chemistry might be more robust or universal than previously believed.
Implications for life’s chemistry: While this doesn’t mean life exists there, it shows the “building blocks” for biomolecules may be widespread — even in harsh cosmic environments. That widens the scope for where life-friendly chemistry could emerge in the universe.
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What Comes Next
The research team plans to expand the search to other protostars in the LMC and possibly in the nearby Small Magellanic Cloud (SMC). By comparing how these organic ices vary across galaxies and environments, they hope to better understand how metallicity, ultraviolet radiation, and dust content influence the formation of complex organic molecules.
They also emphasise the need for more laboratory spectra of these molecules frozen in ices so that the spectral fingerprints can be better understood and matched to observations.
By detecting five large organic molecules including acetic acid in the icy envelope of a protostar beyond our galaxy, scientists have opened a new chapter in astrochemistry. The fact that this happened in the low-metallicity, high-UV environment of the Large Magellanic Cloud suggests that complex organic chemistry one of the precursors to biology may be far more widespread in the universe than previously thought.
Source: Marta Sewiło et al., “Protostars at Subsolar Metallicity: First Detection of Large Solid‐state Complex Organic Molecules in the Large Magellanic Cloud,” Astrophysical Journal Letters, 992(2), L30 (2025).