Key points are not available for this paper at this time.
In 1967 radio observations led to the discovery of very small (d 104 cm -3) H II regions. Ryle from the observed high turbulent velocities (V;:;:: 25 km s -1 ) Mezger et al. (1967b) concluded that the objects must be in a state of rapid expansion, and must represent a very early stage in the life of an OB star. In fact, Vandervoort (1963) and W. G. Mathews (1965) had already pointed out that H II regions with such densities must of necessity undergo rapid expansion and therefore have short lifetimes. The discovery of compact H II regions coincided with their theoretical prediction by Davidson & Harwit (1967), who also drew attention to the strong infnired emission expected from the (predicted) dust cocoon (see also Davidson 1970). The first compact H II regions to be recognized as strong sources of near-infrared emission were W 51-IRS2 and K3-50
Habing et al. (Sat,) studied this question.