Infrared Radiation - Warmth From The Cold of Space

What is Infrared Radiation?

The light we see with our eyes is really a very small portion of what is called the "Electromagnetic Spectrum." The Electromagnetic Spectrum includes all types of radiation - from the X-rays used at hospitals, to radio waves used for communication, and even the microwaves you cook food with.

Radiation in the Electromagnetic Spectrum is often categorized by wavelength. Short wavelength radiation is of the highest energy and can be very dangerous - Gamma, X-rays and ultraviolet are examples of short wavelength radiation. Longer wavelength radiation is of lower energy and is usually less harmful - examples include radio, microwaves and infrared. A rainbow shows the optical (visible) part of the Electromagnetic Spectrum and infrared (if you could see it) would be located just beyond the red side of the rainbow.

Electromagnetic spectrum
Although infrared radiation is not visible, humans can sense it - as heat. Put your hand next to a hot oven if you want to experience infrared radiation "first-hand!

Why study Infrared Radiation from space?

Astronomers have found that infrared radiation is especially useful when trying to probe areas of our universe that are surrounded by clouds of gas and dust. Because of infrared's longer wavelength, it can pass right through these clouds and reveal details invisible by observing other types of radiation. Especially interesting are areas were stars and planets are forming and the cores of galaxies where it is believed huge black holes might reside.

Orion Nebula in optical and infrared
The image on the left shows an optical view of a star forming region. The same area is shown
on the right in infrared radiation. Notice how the infrared observations penetrate the obscuring
cloud to reveal many new details.

How will Gemini "see" infrared better?

Astronomers use special sensors to detect infrared radiation from space, but it's not easy. Because heat is given off by many objects (including the telescope and cameras themselves), everything must be carefully designed, and/or cooled to very cold temperatures.

Gemini South
Gemini has been designed to perform especially well when observing infrared radiation. This includes selecting the locations for the telescopes. Both scopes are located on high mountains where the air is very dry. Since atmospheric water vapor absorbs, or "soaks-up", infrared radiation, this was a very important consideration when selecting the sites for the Gemini telescopes. Gemini will also use special Silver coatings on its mirrors to reflect significantly more infrared radiation than the metals (usually aluminum) used on most other telescope mirrors.

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Peter Michaud / / February 8, 1999