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Across The Universe - Galaxy NGC 474: Shells and Star Streams

14 Feb 2018, 13:49 UTC
Across The Universe - Galaxy NGC 474: Shells and Star Streams
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Galaxy NGC 474: Shells and Star Streams: Discover the cosmos!Each day a different image or photograph of our fascinating universe isfeatured, along with a brief explanation written by a professional astronomer.2018 February 6 Explanation: What's happening to galaxy NGC 474?The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of theelliptical galaxy in less deep images.The cause of the shells is currently unknown, but possiblytidal 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 the spiral galaxy just above NGC 474is causing densitywaves to ripple through the galactic giant.Regardless of the actual cause, thefeatured imagedramatically highlights the increasing consensus that at least some ellipticalgalaxieshave formed in the recent past, and that the outer halos of mostlarge galaxies are not really smoothbut have complexities induced by frequent interactions with -- and accretions of --smaller nearby galaxies.The halo of our ownMilky Way Galaxyis one example of suchunexpected complexity.NGC 474 spans about 250,000light years and lies about 100 million light years distant toward the constellation of the Fish(Pisces).ACROSS THE UNIVERSE

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