Catching a comet streaking across the sky is already a rare treat. This time, though, stargazers are in for something special—not one, but two comets at once. As soon as the Sun sets, it’s worth stepping outside and trying your luck.

While such an event isn’t entirely unprecedented, it’s rare enough to spark excitement among astronomy enthusiasts. Throughout October, observers in the Northern Hemisphere will be able to spot two comets crossing the night sky. Both originate from the distant edges of our Solar System and release gases that give them a distinctive green glow.

A first comet among the shooting stars

The first is comet Lemmon, officially known as C/2025 A6, whose visibility had already been mentioned a few days ago.

Discovered in the United States by the Mount Lemmon Survey, the comet takes its name from the observatory responsible for spotting it.

In recent days, astronomers announced that it had become visible to the naked eye—provided you’re observing from a location free of light pollution.

At the moment, comet Lemmon is moving through the evening sky in Ursa Major, better known as the Big Dipper. Around October 21, it will appear below the handle before continuing toward the constellation Boötes.

That same Tuesday, October 21, the comet will make its closest approach to Earth, passing about 90 million kilometers away. With a new Moon occurring at the same time, moonlight won’t interfere, creating ideal viewing conditions. With a steady tripod, even a smartphone could capture a surprisingly decent photo.

October 21 also marks the expected peak of the Orionids, a meteor shower produced by another famous visitor—Halley’s Comet.

Two comets for the price of one

The second comet, C/2025 R2—better known as Swan—was only discovered last September as it prepared to pass closest to the Sun. It was identified using images from the Solar Wind Anisotropies instrument, which gave the comet its name.

Currently shining at a magnitude of 6, Swan sits right at the threshold of naked-eye visibility. Because comet light is diffuse rather than sharply defined, that limit is harder to judge than it is for stars.

Swan will be the first of the two to pass closest to Earth, doing so on Monday, October 20, at a distance of just 39 million kilometers.

As its trajectory carries it higher in the sky, it becomes easier to observe near the constellations Scutum and then Aquila.

So it’s time to grab your binoculars—and stay alert. Before long, another visitor from deep space, comet 3I/Atlas, could also join the display, making October an unforgettable month for skywatchers.

mayer-nathalie

Nathalie Mayer

Journalist

Born in Lorraine on a freezing winter night, storytelling has always inspired me, first through my grandmother’s tales and later Stephen King’s imagination. A physicist turned science communicator, I’ve collaborated with institutions like CEA, Total, Engie, and Futura. Today, I focus on unraveling Earth’s complex environmental and energy challenges, blending science with storytelling to illuminate solutions.