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<\/a><\/p>\nAn artist\u2019s impression of 3I\/ATLAS is shown as it passes near the Sun, illuminating one side of the comet; 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. Image credit: NSF \/ AUI \/ NRAO \/ M.Weiss.<\/p>\n
\u201cObserving 3I\/ATLAS is like taking a fingerprint from another solar system,\u201d said American University Professor Nathan Roth.<\/p>\n
\u201cThe details reveal what it\u2019s made of, and it\u2019s bursting with methanol in a way we just don\u2019t usually see in comets in our own Solar System.\u201d<\/p>\n
Using ALMA\u2019s Atacama Compact Array in Chile, Professor Roth and his colleagues observed 3I\/ATLAS as it approached our Sun.<\/p>\n
As sunlight warmed its icy surface, the interstellar visitor released gas and dust, forming a coma around its core.<\/p>\n
By analyzing the coma, the astronomers revealed the chemical fingerprints of the material it is composed of.<\/p>\n
They focused on the faint submillimeter fingerprints of two molecules: methanol and hydrogen cyanide.<\/p>\n
The ALMA data reveal that 3I\/ATLAS is heavily enriched in methanol compared to hydrogen cyanide, far beyond what is typically seen in comets born in our own Solar System.<\/p>\n
On two observing dates, the researchers measured methanol\u2011to\u2011hydrogen cyanide ratios of about 70 and 120, placing the object among the most methanol\u2011rich solar system comets ever studied.<\/p>\n
These measurements imply that the icy material from 3I\/ATLAS was formed by \u2014 or experienced \u2014 very different conditions than those that shape most comets in our own Solar System.<\/p>\n
ALMA\u2019s high resolution also allowed the team to see how different molecules move away from the comet, revealing surprising differences between methanol and hydrogen cyanide.<\/p>\n
Hydrogen cyanide appears to come, for the most part, directly from the comet\u2019s core, or nucleus, which is typical for comets in our Solar System.<\/p>\n
Methanol, on the other hand, appears to come from both the nucleus and from ice particles in the coma.<\/p>\n
These tiny, icy grains act like mini-comets: as the object moves closer to the Sun, where ice turns into gas, they also release methanol.<\/p>\n
Similar behavior has been observed in some solar system comets, but this is the first time the physics of such detailed outgassing has been traced in an interstellar object.<\/p>\n
\u201cThe derived methanol\u2011to\u2011hydrogen cyanide ratios in 3I\/ATLAS are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C\/2016 R2 (Pan-STARRS),\u201d the authors said.<\/p>\n