'Once-in-60,000-years' Comet Set to Illuminate October Night Skies

A comet identified last year is set to make its first close approach to Earth in mid-October, according to NASA.

Astronomy enthusiasts recently observed the comet, designated C/2023 A3, in late September during its closest approach to the sun. The comet will reach its nearest point to Earth around October 12, appearing in the western sky of the Northern Hemisphere after sunset, providing stargazers with a chance to observe it.

What's a comet?

A comet is a celestial object made up of ice, dust, and other volatile materials. As comets near the sun, solar radiation causes the volatile substances on their surface to sublimate, releasing gas and carrying dust, which creates the comet's coma and tail.

The C/2023 A3 comet was first discovered by the Xuyi Observation Station of the Purple Mountain Observatory at the Chinese Academy of Sciences on January 9, 2023. It was subsequently confirmed by the International Astronomical Union's Minor Planet Center and was named Tsuchinshan-ATLAS.

Also referred to as C/2023 A3, the "C" signifies a comet that takes over 200 years to complete its orbit around the sun. The number "2023" indicates the year of discovery, while "A" represents the first half of January, and "3" denotes it was the third object discovered during that timeframe.

"After a period of observation, we determined its orbit, and based on the shape of the orbit, we calculated that its orbital period is approximately 60,000 years," Zhao Haibin, a researcher at PMO, told the Beijing News.

Zhao noted that as observational data and non-gravitational influences increase, the comet's orbit might change slightly.

When to see the comet?

Experts believe that stargazers will likely see the comet with the naked eye.

For audiences in the Northern Hemisphere, the comet should be visible shortly after sunset on October 12, low in the western sky within the constellation Virgo. However, the opportunity for naked-eye observation will be limited, lasting only about 10 to 20 minutes, according to Wang Kechao from PMO, who spoke with China Media Group.

In the days following, as the comet moves further from the sun, it will become easier to view with the naked eye, entering its optimal observation period, Wang stated. "About an hour after sunset, it will be visible in the western sky."

By late October, although the comet's brightness will begin to diminish, its increasing distance from the sun will allow for extended observation times. The public can expect viewing opportunities of two to three hours after dark, Wang added.

Due to the comet's parabolic orbit, its brightness will gradually decrease as it travels farther from the sun and Earth, Wang explained. "Based on current predictions, it will become difficult to see with the naked eye around November."

"Naked-eye-visible comets are rare enough as it is, and this one has the potential to be amongst the brightest that we've seen in the last few decades. So it's certainly worth a go," Gregory Brown, senior public astronomy officer at the Royal Observatory Greenwich, told the Guardian.

Jessica Kline for TROIB News