南方天空中的两颗彗星
(原标题: Two Comets in Southern Skies)
2022-10-08
浏览次数: 12
12月20日，彗星C/2017 K2 （PanSTARRS）将接近太阳或近日点，当它掠过地球南半球的天空时，望远镜观测者仍然可以看到它。在9月21日拍摄的一张深度图像中，这颗彗星PanSTARRS首次来自遥远的奥尔特云，在左上角有一个绿色的彗发和大约半度长的白色尘埃尾巴。它还与另一颗彗星73P/Schwassmann-Wachmann 3共用朝向天蝎座的星空视野，这颗彗星位于PanSTARRS右下方约1度。天文学家估计，首次造访的彗星C/2017 K2 （PanSTARRS）已经沿着双曲线轨道从奥尔特云进入地球大约300万年了。不过我们更熟悉Schwassmann-Wachmann 3。这颗周期彗星每5.4年绕自己的椭圆轨道运行一次，从木星轨道的上方绕到地球轨道附近。在9月21日拍摄的这张图片中，这颗彗星刚刚在夜间经过，距离地球约20光分。Schwassmann-Wachmann 3从1995年开始解体，距离我们约7.8光分。
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Heading for its closest approach to the Sun or perihelion on December 20, comet C/2017 K2 (PanSTARRS) remains a sight for telescopic observers as it sweeps through planet Earth's southern hemisphere skies. First time visitor from the remote Oort cloud this comet PanSTARRS sports a greenish coma and whitish dust tail about half a degree long at the upper left in a deep image from September 21. It also shares the starry field of view toward the constellation Scorpius with another comet, 73P/Schwassmann-Wachmann 3, seen about 1 degree below and right of PanSTARRS. Astronomers estimate that first time visitor comet C/2017 K2 (PanSTARRS) has been inbound from the Oort cloud for some 3 million years along a hyperbolic orbit. Schwassmann-Wachmann 3 is more familiar though. The periodic comet loops through its own elliptical orbit, from just beyond the orbit of Jupiter to the vicinity of Earth's orbit, once every 5.4 years. Just passing in the night, this comet PanSTARRS is about 20 light-minutes from Earth in the September 21 image. Seen to be disintegrating since 1995, Schwassmann-Wachmann 3 was about 7.8 light-minutes away.
© Jose J. Chambo