Comet C/2017 K2 PanSTARRS will brighten favourably throughout June
Comet C/2017 K2 PanSTARRS is predicted to continue brightening through June and remains well placed for UK observation. If it follows predictions, it will begin the month with an integrated magnitude of +8.8, making it binocular-friendly.
By the month’s end, it should have brightened to mag. +8.1. The June solstice occurs on 21 June, representing the period when the night skies are brightest for the year. For those in the UK’s far north the eternal twilight is obvious, while those in the south fare better in the middle of the night. This means that although the comet will be brightening over June, so will the sky, only starting to darken subtly by the time the end of the month arrives.
The good news here is that the comet’s brightening will continue beyond June, with it reaching a peak brightness of mag. +7.1 in January 2023. Unfortunately, the UK will lose sight of K2 PanSTARRS well before then as it tracks ever further south to become a target only visible from the Southern Hemisphere.
This month K2 PanSTARRS is well positioned, starting its June track 3˚ to the east of the mag. +3.7 binary star system 72 Ophiuchi. It then appears to move southwest, clipping the southern edge of IC 4665 on the night of 20/21 June. It appears close to mag. +2.8 Cebalrai (Beta (β) Ophiuchi) on the nights of 21/22 and 22/23 June, when it is around 8 arcminutes west of the star at 01:00 BST (00:00 UT) on the 23rd. PanSTARRS’s brightness is estimated to be mag. +8.2, but this is also the time when the sky will appear brightest due to the June solstice.
C/2017 K2 PanSTARRS is an Oort Cloud comet with a hyperbolic orbit. Its closest approach to the Sun is on 19 December 2022.