The star forming region NGC 1999 has long puzzled astronomers because it includes a dark region where there is no emission detected in the optical or near infrared. It was thought that this indicated a region that was heavily obscured by dust. The radiation that would be emitted from this part of NGC1999 would thus be absorbed by dust which would re-readiate the energy at longer wavelengths which Herschel would be able to detected.
The image shows a combination of Herschel and ground-based near infrared data on NGC1999. The important part is the region in the top left, where NGC1999 is coloured green. The hole, seen just to the right of NGC1999, is still there, dark even at Herschel wavelengths. This means there’s no dust there – it’s a hole in the nebula! The suspicion is that this is a hole blown in the material surrounding them by the stars forming in NGC1999. It’s long been known that this must occur if stars are to emerge from their nurseries, but this may be the first time they’ve been caught in the act.
For more information see the ESA discussion of these results.