2025年10月23日
天鹅彗星、天鹅与鹰星云
影像提供与版权: Adam Block
说明: 10月17日，在这张7度宽的望远镜视野中，彗星C/2025 R2（SWAN）呈现出绿色的彗发和较暗的彗尾，在恒星聚集和尘埃星际云的映衬下清晰可见。在这一天，这位内太阳系的新访客巧妙地与银河系中心附近的两个天体鸟类合影留念。靠近画面底部的M16和M17也被深空天文观测者称为鹰和天鹅星云。虽然影像中记录彗发的绿色光芒是由于双原子碳分子气体在阳光下发出萤光，而星云中红色的色调则是距离约5,000光年的恒星形成区域，这是游离氢气体的特征。彗星SWAN现在正在远离地球，但对于可以在北半球傍晚时分靠近南方地平线观测的双筒望远镜和小型望远镜来说，仍然是一颗不错的彗星。C/2025 R2（SWAN）在10月20日最接近我们的地球，仅仅2.2光分的距离。
明日的图片: pixels in space
Due to the lapse in federal government funding, NASA is not updating APOD website. We sincerely regret this inconvenience.
由于美国联邦政府资金中断，NASA目前暂停更新APOD网站。对此带来的不便，我们深感抱歉。
英文原文:
Explanation: Comet C/2025 R2 (SWAN) sports a greenish coma and fainter tail, seen against congeries of stars and dusty interstellar clouds in this 7 degree wide telescopic field of view from October 17. On that date, the new visitor to the inner Solar System obligingly posed with two other celestial birds seen toward the center of our Milky Way. Messier 16, near the bottom of the frame, and Messier 17 are also known to deep skywatchers as the Eagle and the Swan nebulae. While the comet coma’s greenish glow recorded in the image is due to diatomic carbon gas fluorescing in sunlight, reddish hues seen in the nebulae, star forming regions some 5,000 light-years distant, are characteristic of ionized hydrogen gas. Comet SWAN is outbound now but still a good comet for binoculars and small telescopes that can look close to the southern horizon in the northern hemisphere’s early evening skies. C/2025 R2 (SWAN) was closest to our fair planet on October 20, a mere 2.2 light-minutes away.
