It’s likely our last chance to see this comet, last near Earth in the 17th century.
Discovered a mere month ago on 12 August 2023, Comet Nishimura, which could be visible in the night sky tonight, is still somewhat of an enigma. The will-it-won’t-it be visible to the naked eye, is a question that’s on everyone’s lips – but it looks like it could be visible this evening. And while another bright comet, like Neowise, McNaught or Hale-Bopp is what we’re all eager to see, it looks like Nishimura won’t be it.
Although the comet has brightened significantly in the last few days, this icy visitor is now well on its way to approaching perihelion, the place in its orbit when it’s closest to the Sun.
And it’s endured a somewhat perilous journey so far. On 2 September 2023, its luscious, long tail was unceremoniously ripped off by a coronal mass ejection (CME) from the Sun. It’s now ‘regrown’ however, as radiation from the Sun, along with solar wind, has pushed the vaporised ice, dust and dirt out behind the comet. Which helps when you’re trying to spot it.
“While Comet C/2023 P1 Nishimura is relatively bright for a comet, it will be challenging to spot as it won’t be in a favourable position in the sky,” explains Dr Darren Baskill, astronomer and lecturer at the University of Sussex.
But don’t be discouraged. For the most persistent, there’s still one last chance to see this frozen visitor.
When can I see Comet Nishimura tonight?
Comet Nishimura may be visible in the hour after sunset between Thursday 14 September and Sunday 17 September. In the UK, this will be approximately between 7:20pm and 8:20pm.
From now (13 September), we have a short window to view Comet Nishimura in the evening, in the hour after the Sun has set. It’s a short window, but with the Sun now setting around 7:20pm in the UK, not impossible. We’ll be dealing with twilight conditions, rather than the more preferable complete darkness, but with a little luck, may be able to spot this elusive beauty.
Between 13-17 September, in the evening, comet Nishimura will be low on the western horizon, before sinking below the horizon at around 8:30pm. It will rise again the next morning at around 6am, but with the Sun rising just half an hour later, will be hidden by the Sun’s glare in the morning.
It will be in the company of a slim, crescent Moon with a new Moon on 14 September, so it’s a small compensation that interfering light from the Moon will be minimal. Mercury will also be nearby, lingering a little further towards the east.
The 13 and 14 September (and possibly 15 September) should offer the best conditions, becoming increasingly more tricky to spot as we near 17 September. After 17 September it will disappear in the Sun’s glare, before again beginning its outward journey away from the Sun.
The comet made its closest approach to the Earth on 12 September, passing 125 million km (78 million miles) from Earth. It will then reach perihelion on 17 September, passing 43 million km (27 million miles) from the Sun.
It has an estimated orbit of around 430 years, and was last passing near Earth in the 17th century. The next time it’ll be back will be in 2458, if it hasn’t been destroyed by then.
“After the comet’s close approach to the Sun [on 17 September], it will eventually head south of the solar system, where it will only be visible to observers in the southern hemisphere. But even there it will remain hidden by the glare of the Sun until October, by which time it will have faded dramatically,” Baskill adds.
So although it will be visible in the November and December dawn sky, it will be distant and dim, making right now the last (semi-decent) chance to see Comet Nishimura.
How to see Comet Nishimura
To see Comet Nishimura tonight, you’ll need to look to the constellation Leo. The comet will be low on the western horizon this evening, or low on the eastern horizon in the morning.
When the comet was discovered, it was in the constellation Gemini. Since then, it has travelled through Cancer the Crab, and is now in Leo the Lion. It’s making a fleeting visit low on the eastern horizon (just 8 degrees above the horizon) just before sunrise, so you’ll need a clear, unobstructed view towards the east – and near-perfect viewing conditions – to be in with a chance to see it in the morning.
And as it’s always worth repeating: stay well clear of looking directly at the Sun.
The Comet Nishimura meteor shower
There’s some speculation that, although newly discovered, comet Nishimura may be responsible for the Sigma Hydrids meteor shower in December. It’s a minor shower, with an hourly rate of just 3-7, but also relatively faint – especially when compared to the more impressive events like the Perseids and Geminids.
If this is the case, and the shower and Nishimura are related, then we may see the debris field getting ‘refreshed’. More debris from Nishimura’s returning visit may mean – if we’re lucky – a more active shower. So, if elevated activity is recorded this year from the Sigma Hydrids, then this will help confirm that Nishimura as the parent.
Peaking around 7 December, the radiant for the Sigma Hydrids is in the constellation Hydra, the largest of the 88 modern constellations.
About our expert
Dr Darren Baskill is an outreach officer and lecturer in the department of physics and astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich, where he also initiated the annual Astronomy Photographer of the Year competition.
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