A remnant disk around a young massive star

While the formation of low-mass stars has become a well-studied process, it is still difficult to verify a similar evolutionary sequence for massive stars. Although several young stages from massive starless cores to massive protostellar candidates with jets and outflows have been observed, massive star/disk systems whose properties can be inferred uniquely are rare. The final stage of this sequence, i.e., a newborn massive star that is still surrounded by a remnant disk, is missing. This is probably a consequence of the rapid evolution of these systems and the early destruction of the disk in the vicinity of a massive star. We report on an optically visible young massive star (IRS 15) within M17 that displays a huge IR excess. This fortunate coincidence offers the rare opportunity to investigate the star as well as its circumstellar environment in great detail. We have performed both optical and infrared photometry and spectroscopy of the stellar source; in addition, its circumstellar environment has been investigated by mid-infrared imaging. Our data suggest that IRS 15 is a star of about 26 Msolar surrounded by a huge remnant disk of about half a Jupiter mass of dust. From this, we corroborate that massive stars can form by disk accretion and conclude that also their circumstellar disks evolve like those of low-mass stars