Two greenish-hued comets are swinging through the inner solar system this fall, offering a rare chance to spot them in the coming weeks.
The comets, named C/2025 A6 (Lemmon) and C/2025 R2 (SWAN), are visible from the Northern Hemisphere now as their orbits take them through our cosmic backyard on their journey around the sun.
Two comet appearances in the same month are very uncommon.
Both celestial objects can be seen with binoculars or small telescopes through the end of October. Comet Lemmon may be visible to the naked eye when it reaches its closest point to Earth, and is therefore at is brightest, on or around Oct. 21.
Already, some skywatchers have caught sight of these icy wanderers.
Astrophotographer Julien De Winter, a junior lecturer at the University of Mons in Belgium, photographed Comet Lemmon in late September from Texas, capturing its dramatic emerald glow and long tail.
The faint green color comes from the presence of carbon in the cloud of gas that surrounds the comet’s nucleus.
In the Northern Hemisphere from now until midmonth, Comet Lemmon will appear near the Big Dipper before the sun rises, according to EarthSky, a website devoted to skywatching and astronomy. It’s best to look northeast in the sky in the hours before dawn, slightly below the grouping of stars that make up the distinct bowl and handle of the Big Dipper.
In about a week, the comet will instead be visible in the evening sky, rising in the west. From that point through the end of the month, it may be possible to see it with the unaided eye, but these cosmic objects can be tricky to see.
Comet SWAN can be viewed in the evening sky through the end of the month. The best time to spot it will be roughly 90 minutes after sunset, facing southwest. This comet likely won’t be bright enough to see with the naked eye, so binoculars or a small telescope will be necessary.
In the coming days, Comet SWAN will appear higher and higher on the horizon after sunset and may get brighter before it reaches its closest point to Earth on or around Oct. 20.
Under ideal conditions — clear weather, dark skies and as little light pollution as possible — it may even be possible to see both comets on the same night around the end of the month.
Comet Lemmon was discovered in January by the Mount Lemmon Survey, which tracks near-Earth objects using telescopes located in the Santa Catalina Mountains in Arizona.
Comet SWAN’s discovery was even more recent: An amateur astronomer spotted it in early September when sifting through images from the SWAN instrument on NASA’s Solar & Heliospheric Observatory, which launched in 1995 on a mission to orbit and study the sun.
A different type of comet — one from outside our solar system — is also passing through the inner solar system this month. Comet 3I/ATLAS is only the third such interstellar visitor ever confirmed, and it was recently photographed by a spacecraft in orbit around Mars. The interstellar comet will make its closest approach to the sun on or around Oct. 30.
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