Friday, May 16, 2008

The M81/M82 group seen through an Integrated Flux Nebula

I've mentioned Integrated Flux Nebulae before on this blog (see here), but Astronomy Picture of the Day had an awesome picture taken by Jordi Gallego showing the IFN in the region of sky hosting the M81/M82 group a few days ago. The image shown in this post is scaled-down version of Gallego's image that I've flipped to approximately have North up and East to the left, as is standard for astronomical images.

As discussed before, at optical wavelengths Integrated Flux Nebulae (the wispy grey/white filaments in the image) shine by scattering starlight off of the dust grains in the cool filamentary gas that forms the nebula. The IFN is material in our own galaxy, probably at distances of a few hundred parsecs (several hundred light years) from us, while the M81/M82 galaxy group lies much farther away in the background (about 3.6 to 3.9 million parsecs away, about 12 million light years or so).

I only just discovered google sky a few days ago, but what is really neat is that you can actually see these IFN in google sky by clicking on the Infrared tab at the top right. What you're now seeing (or click here for a direct link to the composite google sky image) in red overlaid over the optical image is Infrared Emission as seen by the IRAS satellite --- the dust grains in the IFN not only scatter star light but are heated by it, and they radiate that heat as IR emission.

Note also the bright green blob that is M82, and how much more intense the IR emission from M82 (a dust enshrouded starburst galaxy) is compared to the much larger (and somewhat more normal) spiral galaxy M81. Its a nice visual depiction of the difference in star formation modes in the two galaxies.

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