What will Comet C/2023 P1 do..?


Comet Section Director Stuart Atkinson photographed P1 at 4am on the morning of August 31st from Kendal, Cumbria, using a Canon 700D DSLR znd a 300mm lens on a star-tracking mount. This is a crop from a processed stack of several exposures.

It’s been a while since we’ve had a naked eye comet in the sky, but that might be about to change… possibly…perhaps…

For the past couple of weeks experienced comet observers around the world have been training their telescopes and cameras towards the lower part of the constellation of Gemini, where a comet called C.2023 P1 (Nishimura) has been brightening steadily. P1 is a long period comet which was discovered by Hideo Nishimura on 12 August 2023, using using a 200-mm f/3 telephoto lens mounted on a Canon EOS 6D DSLR camera. Calculations have since shown that it has an orbital period of 437 years.

The comet was in Gemini and shining at around 10th magnitude when it was discovered, but has been brightening steadily and is now around magnitude 7.2, making it a binocular object. The comet has now moved into Cancer, and long exposure images are clearly showing its green hue, and a short, thin tail around one and a half degrees long behind it.

Being in Cancer, the comet is a morning object right now, visible for a short period before sunrise. And this is a problem. As the comet is quite close to the Sun in the sky – and is not going to stray far from it visually – it is quite challenging to see from northern and mid-northern latitudes. Calculations suggest that it might reach a peak brightness of third or even second magnitude after it rounds the Sun in a couple of weeks and swings up into the evening sky, but it will still be firmly embedded in the twilight and will appear fainter than that, probably requiring binoculars to pull it out of the bright sky. Having said that, if the comet grows a decent dust tail after rounding the Sun it might be more obvious, and might be visible to the naked eye, low in the twilight. Or it might not survive its close encounter with the Sun and might “do an ISON” and be broken up into pieces by the Sun’s comet-gobbling gravity. We’ll have to wait and see.

In the meantime, if you want to see this comet at the moment you’ll need to be getting up early, around 3am, and training your binoculars, cameras and telescopes to the north-east, where P1 is waiting for you, not much more than an out-of-focus 7th magnitude star. By mid-September the comet will move up into the evening sky, visible low in the west for a short period after sunset, to the lower left of the curved handle/tail of the Big Dipper/Great Bear, and might be visible to the naked eye. IF it grows a tail itself that might make it easier to see, but there’s absolutely no guarantee of that.

Here are some finder charts to help you look for the comet yourself. Remember, it is very small at the moment, not much more than an out-of-focus star really, and its tail is very faint, so faint it’s only showing up on processed images. Will it get brighter? as I said, we’ll have to wait and see.

Cross those fingers!

1 AM Sept 1-7 0400

3 PM Sept 10-21 1945

4 PM Sept 10-21 2030