The birth of very massive stars is not well understood1,2,3, in contrast to the formation process of low-mass stars like our Sun4,5. It is not even clear that massive stars can form as single entities; rather, they might form through the mergers of smaller ones born in tight groups6,7. The recent claim of the discovery of a massive protostar in M17 (a nearby giant ionized region) forming through the same mechanism as low-mass stars8 has therefore generated considerable interest. Here we show that this protostar has an intermediate mass of only 2.5 to 8 solar masses (M⊙), contrary to the earlier claim of 20M⊙ (ref. 8). The surrounding circumstellar envelope contains only 0.09M⊙ and a much more extended local molecular cloud has 4–9M⊙.
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This Letter is based on data collected at the Subaru Telescope and the Nobeyama Radio Observatory, which are operated by the National Astronomical Observatory of Japan.
The authors declare that they have no competing financial interests.
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Sako, S., Yamashita, T., Kataza, H. et al. No high-mass protostars in the silhouette young stellar object M17-SO1. Nature 434, 995–998 (2005). https://doi.org/10.1038/nature03471