Green Comet Approaching Earth — Visible to the Naked Eye in September
The comet C/2023 P1, also known as Comet Nishimura, is heading towards the Sun. It has been named after the Japanese amateur astronomer Hideyo Nishimura, who first spotted it on August 12 during nighttime observations. Its hyperbolic orbit suggests a potential origin beyond the boundaries of the Solar System, as reported by Business Insider.
On the night sky, Comet Nishimura will reach its peak brightness on September 17 when it will be at a distance of 1.2 billion kilometers from Earth. This comet's visit is a one-time event; the Sun will act like a gravitational slingshot, sending the comet back beyond the Solar System after its passage.
As the comet gets closer to the Sun, it will significantly brighten, providing observers on Earth a chance to see it without telescopes, especially during the early hours of dawn. Currently, its apparent magnitude is around 8, making it visible through telescopes.
Recent photographs of Comet Nishimura have revealed that its coma — the gas and dust cloud surrounding its nucleus — is emitting a green light. This unusual color is due to the splitting of carbon dioxide molecules under the influence of solar light.
If the hyperbolic orbit of the comet is confirmed, it will join the exclusive list of interstellar objects that have visited the Solar System. This list already includes the interstellar comet 2I/Borisov and the enigmatic space rock 1I/'Oumuamua, which caused excitement among scientists and even led to speculations of it being an alien spacecraft.
However, there's also a possibility that the comet originates from the outer region of the Oort Cloud — a reservoir of comets and icy objects beyond Neptune's orbit. It might have journeyed on the outskirts of the Solar System for millennia before reaching us. If that's the case, it implies that the comet orbits the Sun on an extremely elongated path and might visit us again, though probably not for hundreds or thousands of years.
Comet Nishimura isn't the only potential interstellar visitor to our Solar System. In January of this year, Comet 96P/Machholz 1, a non-hyperbolic comet with a height exceeding two-thirds of Mount Everest, was observed during its sixth (and closest) approach to the Sun. This comet was discovered in 1986.
In 2008, chemical analysis of the comet's material highlighted the distinctiveness of 96P/Malchholz 1 from other comets known to originate within the Solar System. Its orbit also brings it closer to the Sun compared to other non-hyperbolic comets. However, these pieces of evidence aren't considered sufficiently convincing to declare this comet an interstellar object.