Two greenish comets will streak through the inner Solar System this fall, providing a rare opportunity to spot them in the coming weeks.
The comets, named C/2025 A6 (Lemmon) and C/2025 R2 (SWAN), are now visible from the Northern Hemisphere as their orbits pass through our cosmic yard on their journey around the Sun.
Two appearances of comets in one month are very rare.
Both celestial objects will be visible through binoculars or small telescopes until the end of October. Comet Lemmon will be visible to the naked eye when it reaches its closest point to Earth and therefore becomes brightest around October 21st.
Some sky watchers have already spotted these icy wanderers.
Astrophotographer Julien DeWinterassistant professor at the University of Mons in Belgium, photographed Comet Lemmon in late September from Texas, capturing its dramatic emerald glow and long tail.
faint green color occurs due to the presence of carbon in the gas cloud surrounding the comet's nucleus.
In the Northern Hemisphere, between now and mid-month, Comet Lemmon will appear near Ursa Major before sunrise. according to EarthSkywebsite dedicated to sky observation and astronomy. It's best to look toward the northeastern sky in the predawn hours, just below the group of stars that make up the distinct bowl and handle of Ursa Major.
In about a week, the comet will be visible in the evening sky, rising in the west. From now until the end of the month it will be visible to the naked eye, but seeing these space objects can be difficult.
Comet SWAN will be visible in the evening sky until the end of the month. The best time to spot it is about 90 minutes after sunset, looking southwest. This comet likely won't be bright enough to be seen with the naked eye, so binoculars or a small telescope will be needed.
In the coming days, Comet SWAN will appear higher and higher on the horizon after sunset and may become brighter before reaching its closest point to Earth on or around October 20.
Under ideal conditions—clear weather, dark skies and as little light pollution as possible—it might 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.
The discovery of Comet SWAN was even more recent: an amateur astronomer spotted it in early September while viewing images from the SWAN instrument on NASA's Solar and Heliospheric Observatory, which launched in 1995 on a mission to orbit and study the Sun.
Another type of comet is one from outside our solar system — also passes through the inner solar system this month. Comet 3I/ATLAS only the third such interstellar visitor ever confirmed, and this was recently photographed spacecraft in Mars orbit. The interstellar comet will approach the Sun around October 30th.
