Where Are All the Baby Stars?

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Not all spiral galaxies are grand and well-defined. Some of my favorites are the fluffy, wispy, flocculent spirals, such as the one shown above. The Hubble Space Telescope‘s Wide-Field Camera 3 reveals NGC 2841 to be quite lovely, but also quite… quiet.

This galaxy was imaged as part of a study of a wide-range of star formation in galaxies. Astronomers have long known that stars are born from collapsing gas clouds, but the details of why and how are still elusive, especially for the most massive stars. Why does one galaxy produce stars at a prolific rate, while others chug quietly along, producing some here and there?

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In more well-defined spiral galaxies, the arms are the site of some kind of density wave, which can encourage gas clouds to collapse and form new stars. A flocculent spiral, however, is a bit messier. Therefore, WFC3 was called in to do the job.

This camera can detect the ultraviolet wavelengths of hot, giant, newborn stars. It is also sensitive in the infrared, which is good for teasing out those forming stars that might be obscured by dust, as is often the case in a star forming region.

These star forming regions in NGC 2841 don’t show any particular pattern, but instead seem to be spread rather evenly throughout the disk. There is no well-defined density wave to be found.

This “ratty” shape may be due to differential rotation, which allows stars to wander away from their neighbors after birth, stretching out a population. After all, spiral galaxies don’t rotate coherently like the blades on a propeller.

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For some more stunning eye-candy, check out this all-infrared image of the same galaxy, taken with the Spitzer Space Telescope. Even when digging into the fascinating astrophysics of these galaxies, it is nice to step back for a moment and say, “Ooo. Pretty!”

Images: Top – NGC 2841 as seen by Hubble. Credit – NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: M. Crockett and S. Kaviraj (Oxford University, UK), R. O’Connell (University of Virginia), B. Whitmore (STScI) and the WFC3 Scientific Oversight Committee. Bottom – NGC 2841 as seen by Spitzer. Credit – NASA/JPL-Caltech