Two newly discovered comets approach Earth this month in rare celestial event

Two newly discovered comets are expected to approach Earth this month, offering a spectacular celestial spectacle for astronomers and space enthusiasts.

Comets consist of ice, frozen gases and rocks, and as they travel near stars like the sun, heat forces them to release gas and dust, creating their characteristic tails.

Researchers located comet C/2025 A6 Lemmon on 3 January, whilst C/2025 R2 SWAN was recently spotted for the first time on 10 September during its close approach to the sun, according to Qicheng Zhang, a postdoctoral researcher studying small body astronomy at Lowell Observatory in Flagstaff, Arizona.

For keen sky observers, this is the right moment to spot the comets with binoculars or telescopes, because both have long-period, oval orbits that lead them around the sun, meaning they will be near Earth for only a limited time.

Comet SWAN will not reappear for another 650 to 700 years, whilst Lemmon will remain out of sight for 1,300 years, said Carrie Holt, a postdoctoral researcher and astronomer at Las Cumbres Observatory, a global network of observatories.

“SWAN is visible only early in the evening—immediately as darkness falls,” Quanzhi Ye, associate researcher at the University of Maryland’s astronomy department, wrote in an email. “Lemmon is now visible shortly before sunrise but will soon become visible only in the evenings and nights.”

Both comets appear near the sun as seen from Earth, so there is only a small time window each day to observe them, Ye added.

SWAN will make its closest approach to Earth—at a distance of 38.6 million kilometres from us—on 20 October, whilst Lemmon will swing to a distance of 88.5 million kilometres from our planet on 21 October, Ye said.

Both comets look similar in images, surrounded by green gas with long tails flowing behind them, Zhang said.

Astronomers are attempting to observe both to learn more about long-period comets, which have orbits lasting 200 years or more.

Long-period comets have spent most of their time at the frozen edge of our solar system, in the Oort Cloud, a spherical shell of frozen bodies, Holt said. These comets most likely formed near giant planets like Jupiter and Saturn, before receiving a gravitational push to the outskirts of our solar system billions of years ago—where they have been preserved in deep freeze ever since, she added.

“When one is pushed back towards the sun, we see materials that have changed minimally from the beginning of the solar system,” Holt wrote in an email.

“As their ice begins to transform from solid to gas, we get a taste of the initial building blocks of our solar system and have the opportunity to learn how planetary systems like ours combine”.

Comet characteristics

Comet Lemmon is visible to those living in the Northern Hemisphere, whilst SWAN favours sky observers in the Southern Hemisphere—but is also becoming visible in the Northern Hemisphere, Ye said.

Lemmon is expected to become brighter over the coming weeks until early November, whilst SWAN will most likely fade soon, he added.

Comet Lemmon will also hide behind the sun in November and December and then become visible only to observers in the Southern Hemisphere.

Ukrainian amateur astronomer Volodymyr Bezuglyi discovered comet SWAN through images captured by the Solar Wind Anisotropies instrument on the Solar and Heliospheric Observatory spacecraft, a joint NASA and European Space Agency programme studying the sun.

Lemmon was located by Mount Lemmon Observatory in Arizona as part of the Catalina Sky Survey, a NASA-funded project that scans the night sky for near-Earth objects such as asteroids that could pose a danger to Earth.

How to spot the comets

Holt recommends people use binoculars and observe from a dark area away from light pollution. Numerous apps can show where the comets are in real time, she said.

“You can even try to see it with your phone’s camera,” Holt said, “changing the settings to greater exposure of a few seconds and aiming it at the sky”.

If the sky is not clear in your area on the evening of 20 October, the Virtual Telescope Project will share a live broadcast of both comets from telescopes under the dark sky in Manciano, Italy.

(information from skai.gr)