2025年9月26日
A SWAN, an ATLAS, and Mars
Image Credit & Copyright: Adam Block
Explanation: A new visitor to the inner Solar System, comet C/2025 R2 (SWAN) sports a long ion tail extending diagonally across this almost 7 degree wide telescopic field of view recorded on September 21. A fainter fellow comet also making its inner Solar System debut, C/2025 K1 (ATLAS), can be spotted above and left of SWAN’s greenish coma, just visible against the background sea of stars in the constellation Virgo. Both new comets were only discovered in 2025 and are joined in this celestial frame by ruddy planet Mars (bottom), a more familiar wanderer in planet Earth’s night skies. The comets may appear to be in a race, nearly neck and neck in their voyage through the inner Solar System and around the Sun. But this comet SWAN has already reached its perihelion or closest approach to the Sun on September 12 and is now outbound along its orbit. This comet ATLAS is still inbound though, and will make its perihelion passage on October 8.
Tomorrow’s picture: light-weekend
天鹅彗星、阿特拉斯彗星与火星
影像提供与版权: Adam Block
说明: 9月21日，C/2025 R2（天鹅 SWAN）彗星作为内太阳系的新访客，其长长的离子彗尾斜跨在近7度宽的望远镜视野中。另一颗较暗的彗星C/2025 K1（阿特拉斯 ATLAS）也首次造访内太阳系，它位于天鹅彗星绿色彗发的左上方，在室女座星海背景的映衬下清晰可见。这两颗新彗星都是在2025年才被发现的，并在这一幅天体图像中与红色的火星（底部）相伴，火星是地球夜空中更常见的流浪者。这些彗星似乎在赛跑中，几乎并驾齐驱地穿越内太阳系并绕行太阳。但这颗天鹅彗星已经在9月12日抵达近日点，即最接近太阳，现在正沿着其轨道向外运行。不过，这颗阿特拉斯彗星（ATLAS）则仍在向内移动，将于10月8日通过近日点。
明日的图片: light-weekend
