Astronomers have discovered a second interstellar cloud near the center of the Milky Way that is extraordinarily rich in complex molecules, including several molecules associated with prebiotic chemistry. The newly studied cloud, G+0.633-0.0604, or G+0.633, contains more than 120 identified molecular species and is the first confirmed chemical twin of another famous molecule-rich cloud. Their paper, posted to the arXiv preprint server on Aug. 14, outlines the chemistry of the newfound cloud.
Under the right conditions
Finding molecules in space isn’t new. So far, astronomers have found almost 350 different molecules in interstellar space. Most recent progress has been concentrated around a small handful of unusually chemically rich locations—the most famous being a molecular cloud called G+0.693-0.027, or G+0.693 for short, near the crowded, extreme region surrounding the Milky Way’s central black hole.
This cloud contains roughly 40% of all molecules ever detected in interstellar space, including many linked to the chemical building blocks of life. Interestingly, it is not actively forming stars. Instead, its chemical richness comes from a combination of physical and chemical properties. The cloud is warm enough to sustain plenty of chemical activity, but the molecules emit significantly cleaner, easier-to-read “cool” signals.
The cloud is also thought to have been stirred up by low-velocity shock waves, likely from colliding gas clouds. The shock waves might violently blast icy coatings off dust grains, releasing a wide variety of molecules that had been frozen inside the ice. This leaves more of these molecules in the gas phase, boosting detectability. Astronomers wondered whether this rare combination was unique to this cloud.
A goldmine
Now, in a new study, astronomers have reported another molecular cloud near the Milky Way’s center and call it a “new goldmine for astrochemistry.” G+0.633 sits just 32 light-years (190 trillion miles) from G+0.693 and shares many similarities with it.
Astronomers, led by David San Andrés of the Center for Astrobiology in Spain, found emissions from certain elements that revealed velocities suggestive of a “shock-dominated environment.” They also found a similar temperature mismatch pattern.
When they surveyed it in detail, they found more than 120 different molecules—including several complex, “prebiotic” molecules potentially relevant to the origin of life. As the researchers write in the paper, “This survey has revealed over 120 molecular species containing all six essential biogenic elements (C, H, O, N, P and S), including the aromatic cycle benzonitrile, immediately placing G+0.633 among the richest molecular reservoirs in the galaxy.”
‘Astrochemical twin’
Among these findings, three molecules tied to life’s basic chemistry stand out. Ethanolamine, a key building block of the biological membranes that enclose living cells, was detected for only the second time in space. Sp-glycolamide, a structural twin of glycine—the simplest amino acid, which the body uses to build proteins—also marks a second-ever detection. And all three versions of cyanomethanimine were found.
These molecules are thought to be building blocks of adenine, one of the four genetic “letters” in RNA and DNA. “These detections, together with the remarkable similarity of the overall molecular inventory, establish G+0.633 as the first confirmed astrochemical twin of G+0.693,” the researchers conclude.
Therefore, the remarkable chemistry of G+0.693 may not be a cosmic oddity after all. By finding these same rare, life-relevant molecules in a second cloud, the researchers are strengthening the case that these life-building-block molecules can form reliably wherever the right physical conditions exist.
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Publication details
D. San Andrés et al, The Galactic Centre G+0.633-0.0604 Molecular Cloud: A New Gold Mine for Astrochemistry, arXiv (2026). DOI: 10.48550/arxiv.2608.14381
Journal information:
arXiv
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More than 120 molecular species found in giant cloud near Milky Way’s center (2026, September 2)
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