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Starry continent shines brighter

L. Rebull / Caltech / JPL / NASA

Four views of the North American Nebula show how different wavelengths provide different perspectives on astronomical objects. The visible-light view at upper left highlights the nebula's similarity to the continent. The red region to the right is known as the "Pelican Nebula" due to its birdlike appearance. The upper-right view includes both visible and infrared observations. In the two lower views, only the infrared readings from Spitzer are displayed. Click on the image to download larger versions.

North America has been thoroughly explored, but the North America Nebula is a different matter entirely. Fresh infrared images of the continent-shaped star-forming region, lying in the constellation Cygnus, reveal thousands of stars that can't be seen in visible light. The new pictures come from NASA's Spitzer Space Telescope, whose infrared-sensitive cameras are designed to cut through interstellar dust and spot the glittering prizes within.

Previously, only about 200 stars could be seen — but the new observations, accepted for publication in the Astrophysical Journal Supplement Series, add more than 2,000 candidate stars to the list.

You can see how the North America Nebula (or is that the North American Nebula?) got its name by looking at the visible-light view in the upper-left quadrant of the image above. The relatively bright area toward the left is reminiscent of the eastern United States and Mexico. The dark, central knots of cosmic dust stand in for the Atlantic and the Gulf of Mexico. There's a reddish swirl of dust on the right side of the picture that is known as the Pelican Nebula, again because of its shape. Can you see the pelican's long beak?

All these features seem to disappear in the Spitzer views at lower left and right, because the space telescope's cameras can cut through the dark areas of the "Gulf of Mexico" dust cloud. Different colors stand for different wavelengths of infrared light detected by Spitzer's infrared array camera and multiband imaging photometer. This "Hidden Universe" video guides you through the imagery:

"One of the things that makes me so excited about this image is how different it is from the visible image, and how much more we can see in the infrared than in the visible," the study's lead author, Luisa Rebull of NASA's Spitzer Science Center at the California Institute of Technology, said today in an image advisory. "The Spitzer image reveals a wealth of detail about the dust and the young stars here."

There are a few mysteries left to solve. For example, astronomers aren't sure exactly how far away the nebula is, for example. Further observations from Spitzer could refine the current estimate of 1,800 light-years. Another puzzler has to do with the nebula's power source. There should be some massive stars that dominate the nebula and drive the formation of later generations of stars, but not even Spitzer was able to find them. The clues so far suggest that the bright stars are still hidden behind the central "Gulf of Mexico" clouds.

More examples of infrared imagery:

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