When you go out to find Orion later this year, it’s a safe bet that what you see through your binoculars or small telescope (or even the naked eye) will be limited to optical wavelengths of light — that is, the light your eyes are most sensitive to. That makes sense, since that’s what “optical” means. But, what if you had eyes that were sensitive to infrared light — specifically to the 1.2 to 2.2 micron infrared wavelength range, and you could zoom in on the constellation Orion and the nebula that lies just beneath the three stars that make up the belt of Orion? You might see something that looks like this 2MASS image.
I’ve discussed the Nebula in this blog before — it’s one of my favorite places to study in the winter sky (and is a familiar summer sight for southern hemisphere stargazers). The nebula contains one of the closest star formation regions in our neck of the galaxy. Small wonder that it’s one of the most heavily studied areas of the sky. Every major observatory ranging from the likes of Hubble Space Telescope to the smallest amateur facility has a picture or some data set relating to this nebula.
The visible part of this nebula is only a small part of a huge cloud of gas and dust spread out across the region of the galaxy where the nebula and its “trapezium” of newborn stars inhabit. The whole complex is called the Orion A Molecular Cloud and it is a huge storehouse of containing the raw materials for star formation. Newborn stars already formed in this “stellar nest” are lighting up the rest of the cloud, which enables us to see it from across 1,500 light years of space.
This 2MASS infrared view of the Nebula looks quite different from the many colorful optical light images we’re all used to seeing in books, magazines, and spread out across the planetarium dome. The light we see with our eyes and in those optical photos is given off by glowing gases in the nebula, or reflected off of dust grains. Those gas and dust clouds hide other objects in the nebula. In infrared light the obscuring clouds of dust are more transparent, allowing us to see deeper into the Orion Nebula and revealing the otherwise hidden stars and other objects scatted throughout the region. None of the reddest objects in this picture can be seen in visible light!
If you’d like to look at other familiar sky objects with an infrared eye, take a look at the 2MASS web site. What you see will give you a greater appreciation for how the universe looks through infrared eyes!
