Wisconsin Sky Watchers’ Last Chance to See Comets Lemmon, SWAN & Orionid Meteor Shower

Wisconsin sky watchers have a final chance to see two comets, along with a meteor shower, this week

Sky watchers in Wisconsin have this week as their last opportunity to observe two rare comets—Comet Lemmon (C/2025 A6) and Comet SWAN (C/2025 R2)—alongside the Orionid meteor shower, which is near its peak activity. These celestial phenomena offer a spectacular show for both amateur astronomers and the general public, with Comet Lemmon expected to shine brightest near Halloween before retreating for over a millennium.

• Comets Lemmon and SWAN became visible starting Oct. 20, with closest approaches to Earth around Oct. 20–21.
• Comet Lemmon will peak in brightness between Oct. 31 and Nov. 1, potentially visible to the naked eye in dark skies.
• Comet SWAN is fading and requires binoculars or telescopes to be seen, with its last good viewing window from Oct. 24 to 26.
• The Orionid meteor shower is active from Oct. 2 to Nov. 12, with peak activity expected around Oct. 22–23, offering up to 20 meteors per hour in optimal conditions.
• Prime viewing locations in Wisconsin require clear, dark skies free from urban light pollution and weather obstructions.

Overview of Comets Lemmon and SWAN’s Appearance

Two bright green comets, Lemmon and SWAN, originating likely from the distant Oort Cloud beyond Pluto, have captured the attention of sky watchers across the Northern Hemisphere. Comet Lemmon, discovered in January during near-Earth asteroid surveys, reached its closest proximity to Earth on Oct. 21 and will approach the sun closely on Nov. 8. It is expected to shine at its brightest between Oct. 31 and Nov. 1, reaching a magnitude of approximately 4.5—making it visible to the naked eye in areas with low light pollution.

Comet SWAN, spotted in September by an amateur astronomer using NASA and ESA spacecraft data, made its nearest approach to Earth a day earlier on Oct. 20 but is significantly dimmer at magnitude 5.9 and is receding from the sun, dwindling in brightness. It remains visible through early November but will be increasingly challenging to spot without binoculars or a telescope. The weekend of Oct. 24–26 may be the last opportunity to observe Comet SWAN at its peak.

Where and When to See Comet Lemmon and SWAN in Wisconsin

According to the astronomy website EarthSky, Comet Lemmon can be located near certain stars on key dates: on Oct. 25 just after sunset near the star Alphecca in the Corona Borealis constellation, and on Oct. 31 near the star Marfik in Ophiuchus. Observers are advised to face northwest after sunset and use binoculars to assist if needed.

For Comet SWAN, the best viewing is toward the southwest horizon shortly after sunset, in proximity to the Summer Triangle of bright stars—Vega, Deneb, and Altair. It will appear roughly halfway between Altair and the horizon. Given SWAN’s faintness and location, observations are more suitable with optical aid and may be more favorable in the Southern Hemisphere.

Tips for Viewing the Comets

• Arrive outdoors roughly 90 minutes after sunset for ideal visibility.
• Use binoculars or a low magnification telescope for the best chance to spot the faint tails and diffuse comas characteristic of comets.
• Use stargazing apps such as Stellarium, Sky Guide, Sky Tonight, or SkySafari 7 Pro to aid in locating the comets in the sky.
• Seek dark, open places removing yourself from city lights, to maximize visibility.

The Orionid Meteor Shower: Peak and Viewing Advice

The Orionid meteor shower, associated with debris from Halley’s Comet, is active from Oct. 2 through Nov. 12. It is known for bright, fast meteors and fireballs. NASA estimates the peak activity to be between Oct. 22 and Oct. 23, though some reports mark Oct. 21 as the peak. During peak times, observers in Wisconsin can expect to see up to 20 meteors per hour.

The best observation window for the Orionids occurs from just before midnight until about 2 a.m. Meteor streaks often appear to radiate from the Orion constellation in the southeastern sky, but meteors can be seen streaking across any part of the night sky.

Best Viewing Locations in Wisconsin

To maximize the viewing experience for these celestial events, clear skies without cloud cover or haze are essential. Planning according to weather forecasts is strongly recommended. Some of Wisconsin’s best places to enjoy night sky phenomena include remote, rural areas with minimal light pollution.

Scientific and Historical Context of the Comets

Comets are remnants from the solar system’s formation over billions of years ago, composed largely of ice and dust. They gain their distinctive glowing comas and streaming tails as they approach the sun and the solar heat causes gases to sublimate from their surfaces.

• Comet Lemmon follows an elongated orbit with an estimated 1,350-year period, having had its orbital path altered slightly by Jupiter’s gravity. It will not return until approximately the year 3179.
• Comet SWAN has an extremely long orbital period of about 20,000 years and is currently moving away from the sun after its close passage.

Previous Cometary Sightings and Significance

Rare double simultaneous cometary displays without specialized equipment occur infrequently, and while rare, they have been observed before. Notable past comets visible from Earth include Comet Tsuchinshan-Atlas (2024), Neowise (2020), Hale-Bopp, and Hyakutake (1990s). Earlier this year, hopes for a bright green comet spectacular were dashed when a similar green comet broke up during a solar flyby.

Both Lemmon and SWAN’s visible green color comes from gases streaming from their surfaces, although to the naked eye they appear as grayish, fuzzy patches of light.

Conclusion

For residents of Wisconsin and neighboring areas, this week offers a remarkable celestial opportunity with two rare comets grace the night sky along with the active Orionid meteor shower. With proper timing, location, and some optical aid, sky watchers can enjoy a once-in-a-lifetime spectacle that will not repeat in their lifetime.

Contributions and Credits

The report draws on insights from institutions such as the Royal Astronomical Society, NASA, SpaceWeather.com, EarthSky, Forbes, and contributions from journalists and astronomy experts, ensuring accurate and timely information for celestial event enthusiasts.