Galaxies - Glittering Lights - Marco Lorenzi
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Shell Galaxies (NGC474 and NGC467)

Shell Galaxies (NGC474 and NGC467)

What's happening to galaxies NGC 474 and NGC 467? The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of the elliptical galaxy in less deep images. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where the ongoing collision with NGC 470, the spiral galaxy to the right of NGC 474, is causing density waves to ripple though the galactic giant. Regardless of the actual cause, the above image dramatically highlights the increasing consensus that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with -- and accretions of -- smaller nearby galaxies. The halo of our own Milky Way Galaxy is one example of such unexpected complexity. NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish Pisces. (Text adapted from APOD).

RCOS 14.5" f/9 - APOGEE U16 - L (240m) R (40m) G (40m) B (40m) - Lightbuckets LB003, NM, USA

NGC474NGC 470NGC 467