A newly discovered green comet, named Nishimura, has successfully navigated its close encounter with the sun and is now embarking on a journey back to the outer regions of our solar system. It won’t grace our skies again for approximately 430 years, but its visibility in the coming weeks depends on your location.
Comet Nishimura, also designated as C/2023 P1, was initially detected hurtling towards the sun on August 12 by the amateur Japanese astronomer Hideo Nishimura. The comet displays a vibrant green hue due to its abundant dicarbon content in the coma, the cloud of gas and dust enveloping its solid nucleus.
Initially, the trajectory of the comet suggested that it might be an interstellar visitor akin to ‘Oumuamua or Comet 2I/Borisov, making a singular passage through our solar system. However, subsequent observations revealed an extremely elliptical orbit that brings it into the inner solar system only once every 430 years before slingshotting around the sun and returning to the Oort Cloud, a repository of comets and icy bodies beyond Neptune’s orbit.
On September 12, Comet Nishimura made its closest approach to Earth, coming within 78 million miles (125 million kilometers) of our planet, roughly 500 times the average distance between Earth and the moon. On September 17, it reached perihelion, the closest point to the sun, skimming within 20.5 million miles (33 million km) of our star.
Approaching the sun poses a perilous risk to comets, as the heightened heat and radiation can cause them to fragment into smaller pieces. Remarkably, Nishimura seems to have largely survived this ordeal, as reported by Spaceweather.com.
As Comet Nishimura continues to move away from the sun and closer to Earth, it will marginally brighten as more sunlight reflects off its coma, which has expanded slightly due to its near encounter with the sun. However, this doesn’t necessarily imply that it will be more visible to us. The comet’s trajectory and its proximity to the sun only permit sightings near the horizon shortly before sunrise or just after sunset. Moreover, it has dimmed considerably since its approach to Earth, when it was visible to the naked eye. Consequently, observing the comet requires a powerful telescope or specialized astrophotography equipment. Astrophotographer Petr Horalek captured a somewhat blurry image of the comet on September 17 above Slovakia’s Mount Lysa, shortly after perihelion, but he couldn’t discern it without his equipment.
If you reside in Australia, your chances of spotting Nishimura with the naked eye are somewhat better over the next week. Between September 20 and September 27, the comet will set about an hour after the sun, providing a greater separation from our star during this period. This increased separation will enhance its visibility for observers in this part of the world, as reported by Space.com, a sibling site of Live Science.
Nevertheless, there’s hope for the rest of us to catch a glimpse of the comet later in the year, or even fragments of it. Some experts speculate that Nishimura might be the source of the annual Sigma-Hydrids meteor shower, a minor shower that typically peaks in early December, according to the astronomy news site EarthSky. If this hypothesis proves true, Nishimura’s passage could amplify this year’s meteor shower, making it more visually spectacular than usual. Further observations in December will contribute to confirming or disproving this theory.