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New view of
North America Nebula

Posted: 11 February 2011

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More than 2,000 candidate stars have been detected in the North America Nebula thanks to the infrared eyes of the Spitzer Space Telescope.

Previously only 200 young stars were known to exist in the nebula – which takes its name from the shape of the continent of North America, complete with the Gulf of Mexico – because newborn stars are swathed in blankets of dust that are hidden in visible light images. Thanks to Spitzer's penetrating infrared eyes, it can pierce these dusty cloaks to reveal the locations of new star-forming regions.

The changing face of the North America Nebula, here seen in visible light (top left), visible and infrared (top right), infrared (bottom left) and infrared with multiband imaging (bottom right). Dust clouds in the visible image become transparent in Spitzer's infrared views. Image: NASA/JPL-Caltech/L. Rebull (SSC/Caltech).

“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,” says Luisa Rebull of NASA’s Spitzer Science Center, and lead author of a paper about the observations, which will appear in the Astrophysical Journal Supplement Series. “The Spitzer image reveals a wealth of detail about the dust and the young stars here.”

As a star forms inside a collapsing ball of gas and dust, material flattens out into a disc that spins around the forming star, with jets of material bursting out above and below the disc. Planets may form within the dusty disc before it disperses. Examples of all stages of a young star's life can be tracked in Spitzer's view.

The latest view of the North America Nebula from Spitzer, which contains data from both its infrared array camera and multiband imaging photometer. Light with a wavelength of 3.6 microns has been colour-coded blue; 4.5-micron light is blue-green; 5.8-micron and 8.0-micron light are green; and 24-micron light is red. Image: NASA/JPL-Caltech/L. Rebull (SSC/Caltech).

“This is a really busy area to image, with stars everywhere, from the North America complex itself, as well as in front of and behind the region,” says Rebull. “We refer to the stars that are not associated with the region as contamination. With Spitzer, we can easily sort this contamination out and clearly distinguish between the young stars in the complex and the older ones that are unrelated.”

A group of massive stars is thought to be powering the nebula, but as yet remain unidentified. The new Spitzer images hint that these 'missing' stars could be lurking behind the Gulf of Mexico portion of the nebula, their illumination spilling out from behind the dark clouds there. Further observations will help solve this mystery, as well as refining the distance to the nebula itself, which is currently estimated as around 1,800 light years from Earth.

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