2025年6月30日
NGC 4651: The Umbrella Galaxy
Image Credit: Rabeea Alkuwari & Anas Almajed
Explanation: It’s raining stars. What appears to be a giant cosmic umbrella is now known to be a tidal stream of stars stripped from a small satellite galaxy. The main galaxy, spiral galaxy NGC 4651, is about the size of our Milky Way, while its stellar parasol appears to extend some 100 thousand light-years above this galaxy’s bright disk. A small galaxy was likely torn apart by repeated encounters as it swept back and forth on eccentric orbits through NGC 4651. The remaining stars will surely fall back and become part of a combined larger galaxy over the next few million years. The featured deep image was captured in long exposures from Saudi Arabia. The Umbrella Galaxy lies about 50 million light-years distant toward the well-groomed northern constellation of Berenice’s Hair (Coma Berenices).
APOD in a Modern Format StellarSnap
Tomorrow’s picture: eye sky a dragon
NGC 4651: 雨伞星系
影像提供: Rabeea Alkuwari & Anas Almajed
说明: 天空正在下恒星雨。如今我们知道，这个庞大形似宇宙级雨伞的结构，其实是从小伴星系剥离出来的潮汐恒星流。在这幅摄于 阿拉伯的长曝光主题影像里，大星系NGC 4651的宽度和银河系相当，而伞状的结构，则从此星系的明亮盘面向外伸展了大约10万光年。伞状结构的成因，可能是它的伴星系于绕行NGC 4651的椭圆轨道上，反复与大星系近距离接近，因此逐渐受到了拆解。而剥离出来的恒星则会掉入NGC 4651，并在接下来的数百万年里，合并出更大的星系。雨伞星系位于北天的后发座方向，约5千万光年远之处。
现代格式的APOD StellarSnap
明日的图片: eye sky a dragon
