2019 November 16
The Star Streams of NGC 5907
Image Credit & Copyright: R Jay Gabany (Blackbird Observatory) – collaboration; D.Martinez-Delgado(IAC, MPIA), J.Penarrubia (U.Victoria) I. Trujillo (IAC) S.Majewski (U.Virginia), M.Pohlen (Cardiff)
Explanation: Grand tidal streams of stars seem to surround galaxy NGC 5907. The arcing structures form tenuous loops extending more than 150,000 light-years from the narrow, edge-on spiral, also known as the Splinter or Knife Edge Galaxy. Recorded only in very deep exposures, the streams likely represent the ghostly trail of a dwarf galaxy – debris left along the orbit of a smaller satellite galaxy that was gradually torn apart and merged with NGC 5907 over four billion years ago. Ultimately this remarkable discovery image, from a small robotic observatory in New Mexico, supports the cosmological scenario in which large spiral galaxies, including our own Milky Way, were formed by the accretion of smaller ones. NGC 5907 lies about 40 million light-years distant in the northern constellation Draco.
影像提供与版权: R Jay Gabany (Blackbird Observatory) – collaboration; D.Martinez-Delgado(IAC, MPIA), J.Penarrubia (U.Victoria) I. Trujillo (IAC) S.Majewski (U.Virginia), M.Pohlen (Cardiff)
说明: 星系NGC 5907的周围，看似环绕着庞大的潮汐恒星流。这些暗淡的环状结构，从纤细的侧向螺旋盘面向外伸展超过150,000光年。由于它的形貌，NGC 5907拥有木刺星系或刀锋星系的称号。这些只有在极深空影像才得见的恒星流，可能是一个矮星系孑遗的最后身影。这个小星系在过去40亿年之中，被NGC 5907逐渐扯散和合并，现在只剩下这些散落在轨道上的碎片。这幅由小型遥控天文台所拍摄的发现影像，吻合宇宙中像我们银河系这类的大星系，是由小星系吸积而成的想法。星系NGC 5907位在北天的天龙座内，离我们大约有4千万光年远。