A Green Comet Will Be Visible in the Northern Hemisphere on February 1, 2023

After a long absence of 50,000 years, a comet is heading back toward us.

This icy celestial body last made its appearance during the era of Neanderthals, as noted by NASA. It will pass within 26 million miles (42 million kilometers) of Earth on Wednesday before zooming away again, unlikely to return for millions of years.

So, be sure to gaze upwards, in contrast to the title of the film Don’t Look Up.

Having been discovered less than a year ago, this harmless green comet is already visible in the northern night sky through binoculars and small telescopes, and possibly even with the naked eye in the darkest areas of the Northern Hemisphere. It's anticipated to brighten as it approaches and ascends higher in the sky until the end of January, with the best viewing during the pre-dawn hours. By February 10, it will be near Mars, serving as a useful reference point.

Observers in the Southern Hemisphere will need to hold off until next month to catch a glimpse.

Numerous comets have illuminated the night sky over the last year, but according to NASA's comet and asteroid specialist, Paul Chodas, "This one appears to be slightly larger, thus a bit brighter, and it’s approaching closer to Earth’s orbit."

This long-period comet, discovered last March by astronomers at Caltech’s Palomar Observatory using the Zwicky Transient Facility's wide-field camera, is known for its green hue due to the carbon in the surrounding gas cloud, or coma. Its lengthy and cumbersome name is comet C/2022 E3 (ZTF).

On Wednesday, it will speed between the orbits of Earth and Mars at an impressive velocity of 128,500 mph (207,000 kilometers). The nucleus is estimated to be about a mile (1.6 kilometers) in diameter, with tails stretching out millions of miles.

This comet is not anticipated to shine nearly as brightly as Neowise did in 2020, or as Hale-Bopp and Hyakutake did during the 1990s.

However, University of Hawaii astronomer Karen Meech mentioned in an email, "Its brightness will be due to its close passage to Earth, enabling scientists to conduct more experiments and the public to witness a stunning comet."

Researchers are confident in their orbital predictions, indicating that the comet last traversed our solar system's planetary region about 50,000 years ago. However, they are uncertain about how close it came to Earth or if it was visible to Neanderthals, according to Chodas, the director of NASA’s Jet Propulsion Laboratory’s Center for Near Earth Object Studies.

Determining its return is more challenging. Each time the comet passes near the sun and planets, their gravitational influences slightly alter its trajectory, causing significant changes over time. Additionally, jets of dust and gas emitted from the comet as it warms near the sun add an unpredictable factor: "We don’t really know precisely how much they are affecting the comet’s path," Chodas noted.

This comet, a relic from the solar system's formation 4.5 billion years ago, originated from the Oort Cloud, which lies far beyond Pluto. This frigid sanctuary for comets is thought to extend more than a quarter of the distance to the nearest star.

Although comet ZTF originated in our solar system, its future remains uncertain. Chodas explained that if it is expelled from the solar system, it will never return.

Don’t worry if you miss this one. According to Chodas, "In the world of comets, you simply wait for the next one because there are countless out there. The next could be larger, brighter, or even closer to us."