20/09/2023
On top of that, it just so happens the comet and Earth are located at about the worst orientation for viewing: Nishimura will stay close to the Sun as it recedes from us, remaining buried in the star’s glare.
A Short Window to See Nishimura From Australia
Nishimura will soon peek above the western horizon after sunset, but only just. The best chance to see it from Australia comes in the week of September 20 to 27, when the comet’s head will set around one hour after the Sun. It will be farthest from the Sun in the evening sky on September 23.
As twilight ends, Nishimura will be very close to the western horizon, about to set. That means it will probably be lost in the Sun’s glare.
But remember, comets are like cats. Some comets fall apart when at their closest to the Sun, in which case they often brighten significantly. If that were to happen to Nishimura, it could become much easier to spot.
Unfortunately, the comets most likely to fragment are those visiting the inner Solar System for the first time, moving on very long-period orbits of tens or hundreds of thousands of years. Nishimura is a seasoned visitor, with an orbital period of around 430 years. It has likely swung past the Sun many times and survived, which lowers the odds of it breaking apart.
Nonetheless, while the head of the comet might be lost in the twilight, the tail might still be visible as the sky darkens. Before the comet was lost in the glare to northern hemisphere viewers, observers put its tail at around six degrees in length – and it will likely grow as the comet swings closer to the Sun.
If you’re lucky, you might spot the tail standing proud above the horizon as the sky darkens.
