泛星彗星C/2017 K2

Imaged on June 20 2022, comet C/2017 K2 (PanSTARRS) shares this wide telescopic field of view with open star cluster IC 4665 and bright star beta Ophiuchi, near a starry edge of the Milky Way. On its maiden voyage to the inner Solar System from the dim and distant Oort cloud, this comet PanSTARRS was initially spotted over five years ago, in May 2017. Then it was the most distant active inbound comet ever found, discovered when it was some 2.4 billion kilometers from the Sun. That put it between the orbital distances of Uranus and Saturn. Hubble Space Telescope observations indicated the comet had a large nucleus less than 18 kilometers in diameter. Now visible in small telescopes C/2017 K2 will make its closest approach to planet Earth on July 14 and closest approach to the Sun this December. Its extended coma and developing tail are seen here at a distance of some 290 million kilometers, a mere 16 light-minutes away.

這幅廣域望遠鏡照片拍攝于2022年6月20日，在銀河邊緣的富星區(qū)域，泛星彗星C/2017 K2與疏散星團IC4665和亮星蛇夫座β離得很近。這顆泛星彗星是在五年前（2017年5月）被發(fā)現(xiàn)的，當(dāng)時它正在進行從暗淡而遙遠的奧爾特云進入內(nèi)太陽系的首次航程，是在接近太陽的過程中被發(fā)現(xiàn)的最遙遠的活躍彗星，被發(fā)現(xiàn)時距離太陽約24億公里，這距離介于天王星和土星的軌道距離之間。哈勃空間望遠鏡的觀測表明，這顆彗星有一個直徑近18公里的大彗核。C/2017 K2現(xiàn)在已能在小型天文望遠鏡中觀測到，7月14日，它將最接近地球；今年12月，它將最接近太陽。拍這張圖時該彗星距離我們約2.9億公里（僅16光分），可以看到它擴展的彗發(fā)和正在“發(fā)育”的彗尾。