NGC 1999, also known as The Cosmic Keyhole,[1][2] is a dust-filled bright nebula with a vast hole of empty space represented by a black patch of sky, as can be seen in the photograph.

It was previously believed that the black patch was a dense cloud of dust and gas which blocked light that would normally pass through, called a dark nebula.

Analysis of this patch by the infrared telescope Herschel (October 9, 2009), which has the capability of penetrating such dense cloud material, resulted in continued black space.

With support from ground-based observations done using the submillimeter bolometer cameras on the Atacama Pathfinder Experiment radio telescope (November 29, 2009) and the Mayall (Kitt Peak) and Magellan telescopes (December 4, 2009), it was determined that the patch looks black not because it is an extremely dense pocket of gas, but because it is truly empty.

The exact cause of this phenomenon is still being investigated, although it has been hypothesized that narrow jets of gas from some of the young stars in the region punctured the sheet of dust and gas, as well as, powerful radiation from a nearby mature star may have helped to create the hole.