Free Astronomy Magazine May-June 2026

33 ASTRO PUBLISHING strongly enriched in methanol com- pared to hydrogen cyanide. On two observing dates, the researchers measured methanol-to-HCN ratios of about 70 and 120, placing 3I/- ATLAS among the most methanol- rich comets ever studied. These measurements suggest that the icy material making up 3I/ATLAS formed—or was processed—under conditions different from those that shaped most comets in our Solar Sys- tem. Previous observations with the James Webb Space Telescope had al- ready shown that the comet’s coma was dominated by carbon dioxide when it was farther from the Sun. The new ALMA observations add methanol to its unusual chemical in- ventory as another key component. ALMA’s high-resolution imaging also allowed astronomers to study how different molecules move away from the comet. Hydrogen cyanide ap- pears to originate mainly from the comet’s nucleus, which is typical for Solar System comets. Methanol, however, appears to be released both from the nucleus and from icy grains in the coma. These tiny parti- cles act like miniature comets: as they are warmed by sunlight, the ice they contain turns into gas and re- leases methanol into the surround- ing coma. While similar behavior has been observed in some Solar System comets, this is the first time such de- tailed outgassing processes have been traced in an interstellar object. Comet 3I/ATLAS is only the third con- firmed interstellar visitor detected passing through our Solar System, following 1I/‘Oumuamua and 2I/Bo- risov. Observations of these rare ob- jects continue to provide valuable clues about how planetary systems form and evolve across the Galaxy. MAY-JUNE 2026 A n artist's impression of 3I/ATLAS is shown as it passes near the Sun, illuminating one side of the com- et. On the side of the comet closer to the sun, the methanol gas is shown in blue, with icy dust grains still present in the gas. On the dark side of the comet, the hydrogen cyanide is shown in orange. [NSF/AUI/NSF NRAO/M.Weiss] !