6. Comparison with globules in NGC 6611
NGC 6611 is a bright HII region excited by a group of OB stars at a distance of about 2 kpc (e.g. Goudis 1976), and also associated with a number of young intermediate mass stars (e.g. Hillenbrand et al. 1993). The region is famous for its large complex of "elephant trunks", recently imaged with HST by Hester et al. (1996), and likely caused by Rayleigh-Taylor instabilities (Frieman 1954).
Small globules are also found in NGC 6611. Fig. 9 shows an R-band CCD image of a small group of globules. The exciting stars are located towards the upper left corner, and it appears that we see the globules more or less sideways. The southern complex shows the same splintering of globules as seen in IC 2944. The northern globule, on the other hand, is a single unfragmented mass and it has a long tail pointing away from the OB stars. This last feature perhaps indicates that the globule is the remnant of a small elephant trunk, which has been mostly destroyed by the uv radiation. In Fig. 10 another little globule in NGC 6611 is seen. In this image the O stars are towards the top of the figure. The long axis of the little globule is parallel to the large elephant trunks in the region (for a wide field view of the surroundings of Fig. 10, see Spitzer 1954). Part of the base of the elephant trunks is seen in the lower left corner of Fig. 10. This location supports the view that the little globule is the remnant of an elephant trunk.
© European Southern Observatory (ESO) 1997
Online publication: April 6, 1998