IRAS

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Our eyes are finely tuned to see the universe at a narrow range of wavelengths -- a band known as visible light. That provides the best view of things around us, because the energy from the Sun is strongest in that same band.

But the universe is filled with objects that emit much of their energy at other wavelengths. Most of those wavelengths are difficult to study not only because our eyes aren't tuned in to them, but because Earth's atmosphere screens them out.

An example is infrared energy, which has wavelengths that are longer than visible light. In space, infrared comes from relatively cool objects, like spread-out clouds of dust. Water vapor in Earth's upper atmosphere absorbs most infrared energy, so to study the infrared, you have to get high above most of the atmosphere -- on high mountains, higher airplanes, or even higher satellites.

The first infrared satellite, named IRAS, was launched 25 years ago today.

Before IRAS, astronomers had cataloged only a few thousand sources of infrared in all the universe. IRAS found several hundred thousand. It discovered a disk of dust around the star Vega, and saw newly forming stars surrounded by cocoons of dust. For the first time, it peered into the heart of the Milky Way galaxy. And it discovered that wisps of dust fill space like thin clouds.

Like many other orbiting observatories that followed it, IRAS showed us that there's a lot more to the universe than meets the eye.

Script by Damond Benningfield, Copyright 2007

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