Two strange, icy objects in our galaxy that look unlike anything astronomers have ever seen could be an entirely new kind of star.
In 2021, at Niigata University in Japan and his colleagues spotted what appeared to be two icy balls of gas in roughly the same patch of sky, but separated by a large enough distance to be unrelated to each other.
The objects鈥� properties were baffling. They looked like either dense gas clouds or some sort of young star, but they appeared to be isolated from other gaseous or star-forming regions, raising questions of how they might have formed.
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Shimonishi and his colleagues found the objects with data from the Japanese AKARI space telescope, which scanned the Milky Way in infrared light from 2006 until 2011. But the telescope didn鈥檛 have enough resolution to clearly separate which wavelengths of light had which energies, making it even harder to tell what these objects were.
Now, the team has observed the objects with a much more powerful radio telescope, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. But the icy objects still don鈥檛 look like anything astronomers have seen before. 鈥漌e tried our best to reproduce the properties, but currently we cannot find any theories that can explain the spectral energy properties,鈥� says Shimonishi.
The ALMA observations revealed that the two objects must be relatively small compared with other gas clouds, between the size of our solar system and 10 times larger, and they are composed of carbon monoxide and silicon monoxide. The high amount of silicon compared with carbon observed is normally associated with violent cosmic explosions, such as a young star blasting out material, but the objects鈥� small size, isolation and abundance of ice don鈥檛 match up with other known star types, says Shimonishi.
鈥淚t鈥檚 a fascinating piece of work, albeit rather puzzling,鈥� says at the University of Cardiff, UK. 鈥淭he two objects seem to have contradictory characteristics, being cold enough to have abundant ice, but also infrared emission like a star.鈥�
One of the more exciting options for what the objects could be is a new kind of star, says Greaves. But to improve our understanding of them, we first need to better differentiate the two objects, as it isn鈥檛 currently clear how similar they are, she says.
鈥淚t鈥檚 a bit odd that only two of these things have been found and they are both very close in the sky to one another, while at very different distances,鈥� says at Queen Mary University of London. 鈥淚t would be interesting to perform a wider survey to see if more of these objects are discovered.鈥�
Shimonishi and his team have applied for time using the James Webb Space Telescope (JWST) to observe the objects further. 鈥淛WST is very sensitive and has a high spectral resolution, so we can do a very detailed analysis of ice or dust, which can help us understand the thermal history of the source,鈥� says Shimonishi.
arXiv
