The unique shape of the cartwheel galaxy with its huge rim - larger than the diameter of the milky way galaxy - is likely due to a collision with one of the smaller galaxies on the lower left several hundred million years ago 车轮星系独特的外观及庞大的外缘（比银河系的直径还要大）可能起源于几亿年前与左下某个小星系的碰撞。
