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A trio of astronomers with the University of Tokyo and Niigata University has discovered a possible new class of interstellar object. In their study, in The Astrophysical Journal, Takashi Onaka, Itsuki Sakon and Takashi Shimonishi conducted tests surrounding what they describe as two "peculiar embedded icy objects" in interstellar space.

In 2021, researchers studying data from AKARI, a Japanese infrared satellite-based telescope, found two objects that were clearly harboring ices consisting of water and organic molecules. Such ices tend to garner attention because some of them are believed to play a key role in the origins of organic molecules. What made the finding of the new ices surprising was their isolation—such ices are typically found in stellar nurseries.

In this new effort, the researchers took a new look at two icy objects by studying data from ALMA—a Chilean array telescope. They focused most specifically on infrared data from the two objects, expecting molecular emissions associated with star formation.

Instead, they found only molecular emissions of silicon monoxide and carbon monoxide—both of which had compact special distributions that were more compact than observed with other icy objects. The team used that data to determine the chemical composition of the icy objects, along with their sizes, motions and distances from Earth.

They calculated that the icy objects were approximately 30,000 to 40,000 light-years away and found that one of them had a much higher velocity than the other, which suggested they were unrelated to one another. They also noted the absence of submillimeter radiation from either icy object, which was unusual for such objects. They also found that the objects had higher ratios of silicon monoxide to carbon monoxide than other icy objects.

The researchers suggest that the two icy objects are not like others that have been found, making them candidates for a new type of interstellar object. They suggest further study of data from the JWST should help to confirm if that is the case.

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