星系与彗星

2023年10月20日

Galaxies and a Comet
Image Credit & Copyright: Dan Bartlett

Explanation: Galaxies abound in this sharp telescopic image recorded on October 12 in dark skies over June Lake, California. The celestial scene spans nearly 2 degrees within the boundaries of the well-trained northern constellation Canes Venatici. Prominent at the upper left 23.5 million light-years distant is big, beautiful spiral galaxy NGC 4258, known to some as Messier 106. Eye-catching edge-on spiral NGC 4217 is above and right of center about 60 million light-years away. Just passing through the pretty field of view is comet C/2023 H2 Lemmon, discovered last April in image data from the Mount Lemmon Survey. Here the comet sports more of a lime green coma though, along with a faint, narrow ion tail stretching toward the top of the frame. This visitor to the inner Solar System is presently less than 7 light-minutes away and still difficult to spot with binoculars, but it’s growing brighter. Comet C/2023 H2 Lemmon will reach perihelion, its closest point to the Sun, on October 29 and perigee, its closest to our fair planet, on November 10 as it transitions from morning to evening northern skies.

Tomorrow’s picture: observe the Moon

星系与彗星
影像提供与版权: Dan Bartlett

说明: 在这幅10月12日摄于加州六月湖的清晰望远镜影像里，幽暗的天空中到处都是星系。影像所呈现的这片北天猎犬座视野，跨幅将近有2度。其中，最醒目的是左上角，距离约2千350万光年远、亦称为M106的美丽大螺旋星系NGC 4258。而位于中上方的吸睛侧向螺旋星系，则是距离6千万光年的NGC 4217。此外，还可见到恰好穿过这片美丽视野，刚在去年4月发现于莱蒙山巡天影像数据中的莱蒙彗星（C/2023 H2 Lemmon）。拍照时，这颗彗星曳着青绿色的彗发及向视野顶端伸展的暗淡纤细离子尾。这个太阳系内围的访客，目前的距离少于7光分，但用双筒望远镜仍然很难见到它的身影，不过其亮度持续增加之中。彗星C/2023 H2 Lemmon，将于10月29日运行到最靠近太阳的近日点，然后在11月10日来到离地球最近的位置，届时它也从北天清晨的天空移到傍晚的天空。

明日的图片: observe the Moon