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Peculiar icy objects in outer reaches of the Milky Way perplex astronomers

A trio of astronomers from the University of Tokyo and Niigata University have found what they describe as "peculiar embedded icy objects" thousands of light years from Earth. Takashi Shimonishi, Itsuki Sakon and Takashi Onaka have posted a describing their discoveries and offering possible ideas regarding their nature on the arXiv preprint server.

In 2021, two objects were discovered in data from the AKARI space telescope over the years 2006 to 2011. At the time, neither could be identified, leaving the team to wait for additional data from the ALMA array in Chile. Now, the new data have only made the nature of the two objects more mysterious.

The research team has found that both objects, which are near to each other in the night sky but far apart in distance, seem to be ice balls of some sort. Both also reside in an outer part of the Milky Way galaxy. They note that either or both could be dense clouds of gas or a type of star that has not been seen before. The latter possibility seems unlikely though, they note, because both are far from regions in the galaxy where stars typically form.

The research trio explains that infrared data has shown that both objects have absorbed dust and ice, which is typically something seen in young stellar objects—or in background stars positioned behind dense clouds. They note that there is something else odd about the pair—the data from the telescopes do not match regarding their distance apart and from Earth.

Data from one source show one of the objects as 6,500 lightyears from Earth, while data from another source show it as 30,000 lightyears away. Both sources agree that the other object is approximately 43,700 lightyears away. Also, both objects appear to be approximately 10 times the size of the solar system, which the researchers describe as very small for a gas cloud.

The researchers say that other data show that the gas surrounding both objects is made up mostly of silicon dioxide, with a little carbon dioxide mixed in. The ratio, they note, is similar to that seen for young stars. They conclude by suggesting that the available data cannot be used to identify either object. They hope that once the James Webb Space Telescope can be aimed at them, their nature will become more clear.