Astronomers have found that interstellar comet 3I/ATLAS contains an unusually large amount of methanol. Every interstellar object that passes through our solar system offers a rare chance to sample material forged around another star. Now, new observations of comet 3I/ATLAS using the Atacama Large Millimeter/submillimeter Array (ALMA) have revealed a chemical surprise: the comet is [...]

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Title: Protostars at Subsolar Metallicity: First Detection of Large Solid-State Complex Organic Molecules in the Large Magellanic Cloud
Authors: Marta Sewiło et al.
First Author’s Institution: NASA Goddard Space Flight Center
Status: Published in ApJL

Stars and planets form when clouds of molecules collapse in on themselves due to the overwhelming force of gravity (which, relatable). This process is quite mysterious, as these clouds will only live for a couple million years before collapsing, and the newly forming protostars only live for about half a million years before becoming main-sequence stars.

But we are able to find some protostars in the Milky Way and in the Small and Large Magellanic Clouds near us, and observing the molecules around these protostars can help us understand how protostars form.

To look for molecules around protostars, astronomers take spectra of the protostars in the infrared, which is a wavelength region where molecules emit a lot of light. As better instruments are being built, astronomers are more often able to look for what are called complex organic molecules, which are carbon-bearing molecules with at least six atoms.

These complex organic molecules can be detected in different states: most detections have been of gaseous molecules in and around protostars or planet-forming disks, but they can also be found in a solid state on the surfaces of dust grains in the interstellar medium in a galaxy. In this state, they are called complex organic molecule “ices.” These “ices” were rarely found pre-JWST, but since its launch, detections have been more numerous, mainly in the Milky Way. Observing these complex molecules on the surfaces of dust grains tells us more about protostellar dust chemistry, which is an important but still mysterious aspect of star formation.

In this study, researchers look outside of our own galaxy to explore the complex organic molecules in the Large Magellanic Cloud (LMC). The LMC is an interesting place to look for these molecules because it has lower metal content (i.e., elements heavier than hydrogen and helium) than the Milky Way, as well as a harder radiation field. This means photons flying around in the LMC generally have higher energies than photons flying around in the Milky Way, and elements like carbon, oxygen, and nitrogen are less abundant. This is important because these conditions are more similar to what typical galaxies were like in the early universe. Thus the LMC is a better test bed to look at protostars than the Milky Way if we want to understand how stars formed in the early universe.

The authors of this study have found signatures of complex organic molecules in protostars forming in the LMC. They focus on the protostar ST6 in the LMC, shown in the right image in Figure 1. They used JWST’s Mid-Infrared Instrument to take spectra of the region around ST6.

Spectroscopic Signatures of Molecules on Dust Grains

The researchers used the Python tool called dEcompositioN of Infrared Ice features using Genetic Modelling Algorithms (ENIIGMA) to fit the spectroscopy. This code compares the spectra to laboratory data of these complex organic molecules at the temperatures we see in the LMC. The authors fit for complex organic molecules they might expect to see, and they detect methanol (CH₃OH), acetaldehyde (CH₃CHO), ethanol (CH₃CH₂OH), methyl formate (HCOOCH₃), and acetic acid (CH₃COOH); of these, acetaldehyde, ethanol, and methyl formate have never before been detected outside of the Milky Way. Interestingly, this is the first time acetic acid has been definitively detected in any astrophysical environment. The spectral contribution from each molecule is shown in Figure 2; all the individual contributions added together make up the observed spectrum.

These detections provide evidence that these complex organic molecules can be produced on the surfaces of dust grains. Further, their detection in the LMC provides evidence that these molecules can be produced in “harsh” environments like the LMC, with lower metal content and harder radiation fields.

When the authors compared the abundances of these ices to other protostars in the Milky Way galaxy, they found that the abundances are slightly lower around the LMC protostar. This may happen because the dust temperatures are generally higher in the LMC due to the higher-energy photons, which affect the chemistry happening on the dust. Some species they found, however, do have similar abundances to the Milky Way protostars, indicating that the harder radiation field of the LMC does not affect how these species form. Finding more complex organic molecules in the Magellanic Clouds will help us understand further how these compounds form on dust grains and how the galactic environment may affect their formation.

Original astrobite edited by Shalini Kurinchi-Vendhan.

About the author, Caroline von Raesfeld:

I’m a third-year PhD student at Northwestern University. My research explores how we can better understand high-redshift galaxy spectra using observations and modeling. In my free time, I love to read, write, and learn about history.

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To probe the chemistry of cold pre-stellar cores, researchers investigated Lynds 1544 and made the first-ever spatially resolved map of methanimine — a simple molecule that may be involved in the formation of amino acids in space — in this environment.

Astrochemistry at Work

Peering across the galaxy, astronomers have discovered a broad and growing array of molecules, revealing the rich chemistry taking place everywhere from molecular clouds to protoplanetary disks. A central question in astrochemistry is where, when, and how molecules form in space, and how molecules might survive the various phases of star formation and be incorporated into newborn planetary systems, where they could play a role in the construction of complex organic molecules necessary for life.

Today’s research article, led by Yuxin Lin (Max Planck Institute for Extraterrestrial Physics), focuses on a molecule called methanimine (CH₂NH). CH₂NH is the simplest molecule in a class of nitrogen-containing compounds called imines, and it’s thought to be an important stepping-stone in the creation of amino acids.

First Spatially Resolved Map

Lin and collaborators searched for CH₂NH within Lynds 1544 (L1544), a pre-stellar core in the nearby Taurus Molecular Cloud. Pre-stellar cores — condensed, gravitationally bound clumps of cold gas within a molecular cloud — represent an early stage in the process of star formation, just before the gas collapses to form a protostar.

L1544 has been the subject of many astrochemical investigations, and previous studies have revealed that it contains a complex, chemically differentiated envelope surrounding a dense core in which many chemical species have frozen out onto dust grains, leaving the gas depleted of these species.

Using the Institute for Radio Astronomy in the Millimetre Range 30-meter radio telescope, Lin’s team mapped the distribution of CH₂NH across L1544. This isn’t the first time that CH₂NH has been detected in a cold pre-stellar core, but it’s the first time that the molecule has been mapped in a spatially resolved way in such an environment. This allows researchers to compare the distribution of CH₂NH to other molecules in the core and build an understanding of the chemistry behind its formation.

The Chemistry of CH₂NH

The new observations show that CH₂NH can be found throughout L1544, with clear spatial trends in the molecule’s abundance: higher near the outer layers of the core, lower near the center. Using chemical models to aid their analysis, Lin’s team showed that the observed distribution suggests formation pathways driven by moderate amounts of ultraviolet radiation.

In the outer layers of the core, where the gas is less dense, ultraviolet light creates reactive chemical species called radicals that can spur the formation of CH₂NH. In the interior of the core, dense gas prevents the incursion of ultraviolet light. This means that few radicals are created that can help form CH₂NH molecules, and the molecules that do form tend to freeze out onto dust grains, disappearing from the gas.

The discovery of CH₂NH throughout L1544 suggests that the precursors to complex organic molecules can form during the cold, calm pre-stellar core phase of star formation, allowing these molecules to be inherited by nascent planetary systems.

Citation

“First Mapping of Prebiotic Molecule CH₂NH in a Prestellar Core,” Yuxin Lin et al 2026 ApJL 996 L32. doi:10.3847/2041-8213/ae2c76

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