Sword of Orion

In the constellation of Orion, the hunter's belt is seen as three distinctive stars in a row. Hanging just "below" this belt is a fuzzy region, easily seen with the naked eye on a dark night, which is known as the "Sword," or "Great Nebula" of Orion.

At a distance of 1500 light years, this is the nearest large region of star formation and is one of the most intensly studied regions of the sky. A giant stellar nursery, the Orion nebula is home to thousands of young stars, some of which are known to have disks of dust that may be forming new planets. At its core, a cluster of four massive stars (known as the Trapezium) provide most of the energy that causes this nebula to glow.

In fact, the visible part of this nebula is just the glowing tip of a much larger cloud of dust and gas extending up and to the left. Known as the Orion A Molecular Cloud, this vast storehouse of material that can form new stars is hard to see except where hot, young stars have burst out and illuminate its surface.

This infrared view of the Orion Nebula looks markedly different than the many familiar images taken in visible light. One reason is that hot, ionized gas emits much more visible than infrared light, mostly in the red part of the spectrum. However, in the infrared the obscuring clouds of dust are more transparent, allowing us to see deeper into this star forming region and revealing otherwise hidden stars. None of the reddest objects in this picture can be seen in visible light!