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Orion Nebula reveals an infrared rainbow

The sparkles of hidden stars are revealed in a picture of the Orion Nebula that shows off the colors of the infrared rainbow.

Do you see those twinkling lights, strung along a line that starts at the top right corner of the image? Those are stars in the earliest stages of their evolution, swathed in clouds of gas and dust. Astronomers focused on those protostars with the infrared-sensitive cameras of NASA's Spitzer Space Telescope and the European Space Agency's Herschel space telescope.

This color-coded image shows the scene as observed by Spitzer in one set of infrared wavelengths (8.0 and 24 microns, shown here in shades of blue), and by Herschel in somewhat longer wavelengths (70 and 160 microns, shown in green and red, respectively). Herschel monitored the emissions from cold dust particles once a week for six weeks, while Spitzer kept track of the emissions from the warmer dust, filling out the infrared rainbow.

Astronomers found that the stars' brightness in infrared wavelengths varied by more than 20 percent during the observational time frame. That's surprising, because the astronomers expected variations in brightness to play out over a time frame measured in years or even centuries rather than weeks.

What could cause the short-term twinkling? The astronomers theorized that lumpy filaments of gas might be streaming inward from a star's outer environs, temporarily warming up the dusty disk of material surrounding the star. An alternative hypothesis would be that material occasionally piles up on the inner edge of the disk, casting 'shadows" that temporarily darken the outer disk. In any case, the observations from Herschel and Spitzer show that the birth process for baby stars is a rough-and-tumble affair, with significant ups and downs.

Members of the Herschel science team, led by Nicolas Billot, an astronomer at the Institut de Radioastronomie Millimetrique in Grenada, Spain, are preparing a paper about their findings.

"Herschel's exquisite sensitivity opens up new possibilities for astronomers to study star formation, and we are very excited to have witnessed short-term variability in Orion protostars," Billot said today in a photo advisory. "Follow-up observations with Herschel will help us identify the physical processes responsible for the variability."

More infrared wonders:


Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.