Spitzer Space Telescope

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[audio: Spitzer launch; fade out rocket sound under narration]

The Milky Way arcs high overhead on August evenings -- the combined light of millions of stars in the disk of our home galaxy. From outside the glare of city lights, you'll see its subtle glow, with dark "voids" running down its middle.

But don't let appearances fool you. Those dark zones are anything but empty. They're vast clouds of dust, which absorb the light of the stars beyond them. And if our eyes were tuned to a different band of energy -- the infrared -- those clouds would glow brighter than most of the stars.

Astronomers have studied these and other infrared objects with Spitzer Space Telescope, which was known as "SIRTF" when it was launched five years ago today.

Spitzer has provided a dramatic new view of the Milky Way galaxy. It's mapped giant stellar nurseries, and revealed thousands of infant stars. It's also revealed thousands of old stars, which have wrapped themselves in cocoons of gas and dust. And it's helped produce the best map of the Milky Way to date. The map reveals that the Milky Way probably has two major spiral arms wrapping around a long "bar" of stars in its center.

Spitzer has also revealed the nurseries for new planets. The observations are helping astronomers understand how all planets take shape -- including our own.

Despite its contributions, though, Spitzer's time is about up. We'll explain why tomorrow.

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.