Spotlight on Three Comets: Lemmon, SWAN, and ATLAS — What to Watch in 2025

Joy Kumar Sharma8 months ago7 months ago669 mins

Astronomy buffs, prepare for one of the most exciting comet seasons in recent years. Three comets — C/2025 A6 (Lemmon), C/2025 R2 (SWAN), and C/2025 K1 (ATLAS) — are making headlines for their predicted brightness, orbits, and viewing potential. This post brings you the latest on each, plus tips on when and how to see them.

Discovery & Orbit

Discovered on January 3, 2025 by the Mount Lemmon Survey as an apparently asteroidal object. Wikipedia+2British Astronomical Association+2
Precovery images from November 2024 confirmed its cometary nature. British Astronomical Association+3Wikipedia+3Aerith+3
Orbital parameters: perihelion (closest to Sun) at 0.5299 AU, high eccentricity (~0.9957), and a long orbital period (~1,350 years inbound, ~1,155 years outbound). British Astronomical Association+3Wikipedia+3COBS+3

Brightness & Visibility

The comet has already brightened more than originally expected. Some models now predict a peak brightness of magnitude ~4, possibly making it visible to the naked eye in dark skies. Unistellar Science+3Star Walk+3Space+3
It will make its closest approach to Earth on October 21, 2025, at about 0.596 AU (≈ 89 million km) TheSkyLive+2Space+2
It reaches perihelion on November 8, 2025. Unistellar Science+4Wikipedia+4Aerith+4
In late September, it is located in the constellation of Lynx, rising early and visible before dawn in many northern locations. Astro Van Buitenen+3TheSkyLive+3Star Walk+3
Some charts suggest by late October it could be circumpolar at latitudes above ~48° N (meaning it never sets below the horizon). Star Walk+2Space+2

Observing Tips

For best view, use binoculars or a mid-sized telescope early in the morning when the sky is darkest and the comet is highest.
Use star charts or apps (e.g. Stellarium) to track its path through constellations: Lynx → Leo Minor → Ursa Major → Canes Venatici etc. Star Walk+2Space+2
Since comets are unpredictable, monitoring images and magnitude reports from observer networks (e.g., COBS, AERITH) is helpful. Unistellar Science+4COBS+4Aerith+4

2. Comet C/2025 R2 (SWAN)

Discovery & Characteristics

Discovered on September 11, 2025, via the SWAN instrument aboard the SOHO spacecraft by Vladimir Bezugly. Wikipedia+2Space+2
Its orbit is highly elongated (long-period comet), and initial observations place it at magnitude ~6.0. Wikipedia+2TheSkyLive+2

Brightness & Visibility

The comet is becoming more visible, with reports noting a greenish coma and tail captured in recent telescopic images (September 17). EarthSky+1
Some forecasts suggest it may brighten sufficiently to become visible to binoculars or even the naked eye by October (if predictions hold). Space+1
It will pass relatively close to Earth, with its closest approach projected near 0.2606 AU (~38.99 million km) on October 20. TheSkyLive

Observing Tips

Because it lies closer to the Sun’s direction in the sky, visibility will be tricky against twilight glare — early evening or pre-dawn windows may help.
Use telescopes or long-exposure photography to reveal the green coma and faint tail.
Sky mapping tools (e.g. TheSkyLive) provide updated ephemerides (right ascension, declination, rise/set times) to help track its path. TheSkyLive

3. Comet C/2025 K1 (ATLAS)

Discovery & Behavior

C/2025 K1 (ATLAS) is currently less documented in mainstream sources, but it is part of the comet lineup for late 2025. SETI Institute
It passed perihelion on October 8, 2025 (closest to Sun). SETI Institute
Observers note a lack of a clear ion tail, possibly due to depletion in volatile materials like carbon. Facebook

Observing Potential

Post-perihelion, the comet’s survival is not guaranteed — comets often disintegrate during close solar passes. SETI Institute
Its closest approach to Earth is projected for November 26, 2025, making November a critical observation period. SETI Institute

What Makes This Season Special

According to LiveScience, two comets (Lemmon and SWAN) may become visible in the same night, coinciding with the peak of the Orionid meteor shower (October 20–21). Live Science
October 21 also features a new moon, reducing moonlight and improving dark-sky conditions for observing faint comets. Live Science+1
This could mark a rare occasion where bright comets and meteor activity line up, offering observers a spectacular celestial show. Live Science

==> How to Track These Comets Using Stellarium & Apps

https://theskylive.com/planetarium?obj=c2025a6#ra|9.292640143717332|dec|38.650243619643014|fov|80

Add by designation: In Stellarium, use “Comet” mode and enter the comet’s name or designation (e.g., “C/2025 A6”).
Update ephemeris: In extended settings, use an orbital file (e.g. from NASA/JPL or Minor Planet Center) so Stellarium knows its path precisely.
Switch to “All Models” view: This lets you see faint objects — adjust magnitude limits.
Set observing location & time: Match your local coordinates and date/time to see where and when the comet will rise/set.
Use zoom and field-of-view (FoV) presets: You can compare the comet’s location against known star fields to help find it in real sky observations.

Quick Summary Table

Comet	Closest Approach Date	Predicted Brightness	Viewing Window	Key Notes
C/2025 A6 (Lemmon)	21 October 2025	~ magnitude 4 (optimistic)	Late October to early November	Best visibility in Northern Hemisphere; may become circumpolar above ~48° N Aerith+4Star Walk+4Space+4
C/2025 R2 (SWAN)	20 October 2025	~ magnitude 6 → possibly brighter	October	Green coma visible; good candidate binocular object TheSkyLive+2EarthSky+2
C/2025 K1 (ATLAS)	26 November 2025	Unknown / uncertain	November	Survival post-perihelion uncertain; limited data SETI Institute

Final Notes & Advice

These comets’ brightness predictions are not guarantees — comets are notoriously unpredictable.
Use dark skies, binoculars, or telescopes.
Combine your comet viewing with meteor showers (especially in mid-October) for a richer sky experience.
Stay updated with comet tracking services (COBS, TheSkyLive, AERITH) for magnitude updates and orbital refinements.