This glimpse into the heart of the Orion Nebula. This image shows an area a little over one light year across in the central regions of the nebula. The bright newborn cluster of stars to the lower right is the Trapezium. Image source: NASA.

Though not apparent to the naked eye, Orion contains a gigantic dark cloud of matter, the largest such cloud known in the Milky Way Galaxy. Within the Orion Molecular Cloud, new stars are forming, a process that creates a pocket or 'bubble' around the newly emerged stars.

The quadruple star known as the Trapezium is one of these young systems, thought to be little more than 100,000 years old. It started to form just within the edge of the cloud, and its bubble has burst through that edge, leaving us with an illuminated view of the cloud's interior: the Orion Nebula.

The nebula's reddish colouration betrays the predominance of ionised hydrogen in the parent cloud, but more complex molecules such as carbon monoxide have also been detected. Stellar formation in this region of space is still in progress, and infrared observation suggests that at least two new stars will shortly come into existence.