Friday, March 19, 2010

Astrophoto Friday: An Edge-on Sprial Galaxy

This week's astrophoto is a composite image on an edge-on spiral galaxy known as NGC 891. NGC 891 is located some 10 million light years away in the direction of the constellation Andromeda. It has a large dust lane that is typical of spiral galaxies.

It was obtained using the 200-inch Hale Telescope's Wide-field Infrared Camera at Palomar Observatory by Kevin Bundy formerly of the California Institute of Technology and at the 10-meter W.M. Keck Observatory's Low Resolution Imaging Spectrograph (LRIS) by Patrick Shopbell and Judy Cohen of the California Institute of Technology. Yellow colors in this composite correspond to the near-infrared image which was obtained at Palomar. The blue colors correspond to the visible light image which was obtained at Keck.

This kind of representation is useful because it demonstrates the utility of observing at many wavelengths. Because the central bulge of NGC 891 appears yellow in the composite, it is clear that the infrared does a better job penetrating the dust lane of this galaxy, which almost completely obscures the bulge in the optical image.

The Palomar image is the result of the addition of twenty separate frames taken in the Ks filter at 2.2 microns, this observation required a total exposure time of 15 minutes.

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