Explanation: What’s happening to this spiral galaxy? Although details remain uncertain, it surely has to do with an ongoing battle with its smaller galactic neighbor. The featured galaxy is labelled UGC 1810 by itself, but together with its collisional partner is known as Arp 273. The overall shape of UGC 1810 — in particular its blue outer ring — is likely a result of wild and violent gravitational interactions. This ring’s blue color is caused by massive stars that are blue hot and have formed only in the past few million years. The inner galaxy appears older, redder, and threaded with cool filamentary dust. A few bright stars appear well in the foreground, unrelated to UGC 1810, while several galaxies are visible well in the background. Arp 273 lies about 300 million light years away toward the constellation of Andromeda. Quite likely, UGC 1810 will devour its galactic sidekick over the next billion years and settle into a classic spiral form.
Tomorrow’s picture: spot on
说明: 这个螺旋星系发生了什么事？虽然细节仍难以确定，但肯定和它与较小的星系邻居之间的战争有关。这幅影像所呈现的主题星系是UGC 1810，不过它和互撞伙伴合称为Arp 273。 UGC 1810的整体外观，尤其是它的泛蓝外环，可能是猛烈的重力交互作用之产物。这道环的泛蓝色泽，是由刚在过去数百万年内形成的炽热泛蓝大质量恒星所渲染出来的。星系的内围，看来较老较红而且交织着低温的尘埃丝。影像中的数颗明亮恒星，看似远在前景与UGC 1810并无关联，而背景中则可见到数个星系。 Arp 273位在仙女座方向，离我们约有3亿光年远。 UGC 1810很可能在接下来的数十亿年之内，会把它的伴星系吞掉，找回经典的螺旋形外观。
明日的图片: spot on