No high-mass protostars in the silhouette young stellar object M17-SO1


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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Figure 1: Silhouette features of M17-SO1.
Figure 2: Emission features and illustration of M17-SO1.
Figure 3: 13CO 1–0 line images of M17-SO1.


  1. 1

    Yorke, H. W. & Sonnhalter, C. On the formation of massive stars. Astrophys. J. 569, 846–862 (2002)

    ADS  Article  Google Scholar 

  2. 2

    Wolfire, M. G. & Cassinelli, J. P. Conditions for the formation of massive stars. Astrophys. J. 319, 850–867 (1987)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Stahler, S. W., Palla, F. & Ho, P. T. P. in Protostars and Planets IV (eds Mannings, V., Boss, A. P. & Russell, S.) 327–351 (Univ. Arizona Press, Tucson, 2000)

    Google Scholar 

  4. 4

    Mundy, L. G., Looney, L. W. & Welch, W. J. in Protostars and Planets IV (eds Mannings, V., Boss, A. P. & Russell, S.) 355–376 (Univ. Arizona Press, Tucson, 2000)

    Google Scholar 

  5. 5

    Calvet, N., Hartmann, L. & Strom, S. E. in Protostars and Planets IV (eds Mannings, V., Boss, A. P. & Russell, S.) 377–399 (Univ. Arizona Press, Tucson, 2000)

    Google Scholar 

  6. 6

    Bonnell, I. A., Bate, M. R. & Zinnecker, H. On the formation of massive stars. Mon. Not. R. Astron. Soc. 298, 93–102 (1998)

    ADS  Article  Google Scholar 

  7. 7

    Bonnell, I. A., Vine, S. G. & Bate, M. R. Massive star formation: nurture, not nature. Mon. Not. R. Astron. Soc. 349, 735–741 (2004)

    ADS  Article  Google Scholar 

  8. 8

    Chini, R. et al. The formation of a massive protostar through the disk accretion of gas. Nature 429, 155–157 (2004)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Padgett, D. L. et al. Hubble space telescope/NICMOS imaging of disks and envelopes around very young stars. Astron. J. 117, 1490–1504 (1999)

    ADS  Article  Google Scholar 

  10. 10

    Felli, M., Massi, M. & Churchwell, E. A high-resolution study of M17 at 1.3, 2, 6, and 21 CM. Astron. Astrophys 136, 53–64 (1984)

    ADS  CAS  Google Scholar 

  11. 11

    Shuping, R. Y., Morris, M. & Bally, J. A new mid-infrared map of the BN/KL region using the Keck telescope. Astron. J. 128, 363–374 (2004)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Okamoto, Y. K. et al. High-resolution mid-infrared imaging and spectroscopic observations of a massive star forming region W51 IRS 2. Astrophys. J. 553, 254–266 (2001)

    ADS  Article  Google Scholar 

  13. 13

    Ohashi, N., Hayashi, M., Ho, P. T. P. & Momose, M. Interferometric imaging of IRAS 04368 + 2557 in the L1527 molecular cloud core: A dynamically infalling envelope with rotation. Astrophys. J. 475, 211–223 (1997)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Ohashi, N. et al. Rotation in the protostellar envelopes around IRAS 04169 + 2702 and IRAS 04365 + 2535: The size scale for dynamical collapse. Astrophys. J. 488, 317–329 (1997)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Park, S. & Kenyon, S. J. Extended near-infrared emission from candidate protostars in the Taurus-Auriga molecular cloud. Astron. J. 123, 3370–3379 (2002)

    ADS  Article  Google Scholar 

  16. 16

    Tamura, M., Gatley, I., Waller, W. & Werner, M. W. Two micron morphology of candidate protostars. Astrophys. J. 374, L25–L28 (1991)

    ADS  Article  Google Scholar 

  17. 17

    Thi, W. F. et al. H2 and CO emission from disks around T Tauri and Herbig Ae pre-main-sequence stars and from debris disks around young stars: Warm and cold circumstellar gas. Astrophys. J. 561, 1074–1094 (2001)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Jiang, Z. et al. Deep near-infrared survey toward the M17 region. Astrophys. J. 577, 245–259 (2002)

    ADS  Article  Google Scholar 

  19. 19

    Hanson, M. M., Howarth, I. D. & Conti, P. S. The young massive stellar objects of M17. Astrophys. J. 489, 698–718 (1997)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Nielbock, M., Chini, R., Jütte, M. & Manthey, E. High mass Class I sources in M 17. Astron. Astrophys. 377, 273–284 (2001)

    ADS  Article  Google Scholar 

  21. 21

    Hartmann, L. Accretion Processes in Star Formation (Cambridge Univ. Press, New York, 1998)

    Google Scholar 

  22. 22

    Wilson, C. D., Howe, J. E. & Balogh, M. L. The large-scale J = 3 → 2 and J = 2 → 1 CO emission from M17 and its implications for extragalactic CO observations. Astrophys. J. 517, 174–187 (1999)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Howe, J. E. et al. Extended [C I] and 13CO (5 → 4) emission in M17SW. Astrophys. J. 539, 137–141 (2000)

    ADS  Article  Google Scholar 

  24. 24

    Nakano, T., Hasegawa, T. & Norman, C. The mass of a star formed in a cloud core: Theory and its application to the Orion A cloud. Astrophys. J. 450, 183–195 (1995)

    ADS  Article  Google Scholar 

  25. 25

    Kobayashi, N. et al. IRCS: infrared camera and spectrograph for the Subaru Telescope. Proc. SPIE 4008, 1056–1066 (2000)

    ADS  Article  Google Scholar 

  26. 26

    Takami, H. et al. Performance of Subaru adaptive optics system and the scientific results. Proc. SPIE 4839, 21–31 (2003)

    ADS  Article  Google Scholar 

  27. 27

    Kataza, H. et al. COMICS: the cooled mid-infrared camera and spectrometer for the Subaru telescope. Proc. SPIE 4008, 1144–1152 (2000)

    ADS  Article  Google Scholar 

  28. 28

    Hogerheijde, M. R., van Dishoeck, E. F., Blake, G. A. & van Langevelde, H. J. Envelope structure on 700 AU scales and the molecular outflows of low-mass young stellar objects. Astrophys. J. 502, 315–336 (1998)

    ADS  CAS  Article  Google Scholar 

  29. 29

    Ohashi, N., Hayashi, M., Kawabe, R. & Ishiguro, M. The Nobeyama Millimeter Array survey of young stellar objects associated with the Taurus molecular cloud. Astrophys. J. 466, 317–337 (1996)

    ADS  CAS  Article  Google Scholar 

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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.

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Correspondence to Shigeyuki Sako.

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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).

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