三对星系

探索宇宙（universe）！每天都会展示一张我们迷人宇宙的不同图像或照片，并附上一段由专业天文学家（astronomer）撰写的简短解释。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

解释：这些星系对中的每一对都各不相同。顶部的两个星系目前很可能没有相互作用。然而，顶部带有蓝色条纹的星系 NGC 4650A 是一个极环星系（polar-ring galaxy），它可能是过去星系碰撞的结果。图像中间的两个星系看起来似乎正在发生引力相互作用，但它们的相对速度使得这种可能性很小。在这两者中，较大的星系 NGC 4650 是一个旋涡星系（spiral galaxy），其中心有一条明亮的恒星（star）棒。底部的两个星系正在积极地相互作用。大约在十亿年后，NGC 4622A 和 NGC 4622B 可能会合并成为一个单一的星系。所有这些星系很可能都是更大的半人马座（Centaurus）星系团（galaxy cluster）的成员。

Explanation: Each of these pairs of galaxies is different. The two galaxies at the top are likely not interacting, at least presently. However, the top galaxy with the blue stripe, NGC 4650A, is a polar ring galaxy and may be the result of a past galaxy collision. The two galaxies in the middle of the featured image appear like they could be interacting gravitationally -- but their relative speeds make this unlikely. Of these two, the larger galaxy, NGC 4650, is a spiral galaxy with a bright bar of stars across its center. The two galaxies at the bottom are actively interacting. Possibly in a billion years or so, NGC 4622A and NGC 4622B will merge and become one single galaxy. All of these galaxies are likely members of the larger Centaurus Galaxy Cluster.