M94: 双环m/tag/%e6%98%9f" target="_blank">星系
M94: A Double Ring Galaxy
Image Credit & Copyright: Brian Brennan
Explanation: Most galaxies don’t have any rings of stars and gas — why does M94 have two? First, spiral galaxy M94 has an inner ring of newly formed stars surrounding its nucleus, giving it not only an unusual appearance but also a strong interior glow. A leading origin hypothesis holds that an elongated knot of stars known as a bar rotates in M94 and has generated a burst of star formation in this inner ring. Observations have also revealed another ring, an outer ring, one that is more faint, different in color, not closed, and relatively complex. What caused this outer ring is currently unknown. M94, pictured here, spans about 45,000 light years in total, lies about 15 million light years away, and can be seen with a small telescope toward the constellation of the Hunting Dogs (Canes Venatici).
More Availability: APOD now accessible via Flipboard.
Tomorrow’s picture: just so
M94: 双环星系
影像提供与版权: Brian Brennan
说明: 大多数的星系没有任何恒星和气体环，为什么M94有两个？首先，螺旋星系M94有一个由新形成的恒星所构成、围拱在星系核周围的内环，这让它的外观颇不寻常，而且内围也很明亮。较可信的起源假说之一认为，M94内有个旋转的星系棒（长棒状的恒星结），因而于内环所在之处产生一波猛暴的恒星形成。观测还发现了另一个外环，这个外环相当暗淡、色泽有异、并不完整、而且结构相对复杂。不过，这个外环的成因目前不明。这幅影像所呈现的M94，距离我们约1,500万光年远，宽约为45,000光年，用小望远镜即可在猎犬座的方向见到它。
更多可用性: APOD现在可通过Flipboard访问。
明日的图片: just so
