Discovered a mere month ago on 12 August 2023, Comet Nishimura, which could be visible in the night sky tonight, 21 September, 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 on September. In the UK, this will be approximately between 7:20pm and 8:20pm.
From now (21 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.
The comet made its closest approach to the Earth on 12 September, passing 125 million km (78 million miles) from Earth. It reached passed on 17 September, passing 43 million km (27 million miles) from the Sun.
“When a comet undergoes its closest approach to the Sun, the radiation stresses on it are at their maximum," says Professor Don Pollacco from the Department of Physics at the University of Warwick.
"As comets are usually described as a 'dirty snowball', they have low internal strength and some do not survive and evaporate. Comet Nishimura did survive and is now receding from the Sun and heading back into the cold depths of the solar system where it will spend the next 400 years before approaching the Sun again."
To be precise, Nishimura 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 the year 2458 – if it hasn’t been destroyed by then.
How to see Comet Nishimura tonight
Comet Nishimura will be close to the western horizon following the sunset tonight. "It may be seen by eye, but it will still be best to use binoculars. After this it will fade and a telescope will be needed," advises Pollacco.
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 experts
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.
Don Pollacco is a professor at the University of Warwick. His research has been published in journals including Advances in Space Research, and Astronomy and Astrophysics.
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