"A bright spiral galaxy of the northern sky, Messier 63 is about 25 million light-years distant in the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across, about the size of our own Milky Way. Known by the popular moniker, The Sunflower Galaxy, M63 sports a bright yellowish core and sweeping blue spiral arms, streaked with cosmic dust lanes and dotted with pink star forming regions.
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This deep exposure also reveals an enormous but dim arc extending far into the halo above the brighter galactic plane. A collaboration of professional and amateur astronomers has shown the arc to be consistent with the stellar stream from a smaller satellite galaxy, tidally disrupted as it merged with M63 during the last 5 billion years. Their discovery is part of an increasing body of evidence that the growth of large spirals by cannibalizing smaller galaxies is commonplace in the nearby Universe."