Overview: A celestial event in the making
Comet C/2025 A6 (Lemmon) has been a beacon for skywatchers as it brightens on its 1,350-year voyage, approaching its perihelion later this year. The latest images, captured by acclaimed astrophotographer Brennan Gilmore, reveal a dramatic interaction between the comet’s icy nucleus and the solar wind — the stream of charged particles that continually streams from the Sun. On Oct. 2, a long, glowing section of Lemmon’s tail was buffeted and dramatically separated in what scientists describe as a disconnection event, a rare and visually arresting reminder of the Sun’s influence on a comet’s gaseous veil.
What happened during the disconnection event
Gilmore’s 60-minute timelapse shows a substantial chunk of Comet Lemmon’s tail peeling away, clearly illuminated as sunlight reflects off the ejected material. A tidal-like read of the solar wind’s pressure can be seen in real time, as the tail curves, thins, and at times splits under the solar wind’s steady push. These events happen because a comet’s tail is not a solid appendage but a cloud of ions and dust pushed outward by solar radiation and charged particles. The result is a tail that always points away from the Sun, independent of the comet’s flight direction.
Why Lemmon’s tail glows green
Much of Lemmon’s visible glow comes from the coma — the luminous envelope surrounding the nucleus. The greenish tint often traces to diatomic carbon (C2) and cyanogen (CN) molecules excited by solar radiation. As Lemmon brightens ahead of its October close approach, observers are treated to a striking, easy-to-identify spectacle in dark skies. In Gilmore’s images, the green coma radiates against a starry backdrop, with the tail extending far from the nucleus and catching light that makes the disconnection even more dramatic.
Observing Lemmon as it nears perihelion
Though the naked-eye visibility of Lemmon depends on local light pollution, some observers report magnitudes around +5.1 under dark skies. This places Lemmon on the threshold of naked-eye visibility for experienced skywatchers, a tantalizing prospect for October when the comet reaches perihelion near the Sun (November 8). The heightened activity as Lemmon nears perihelion often translates to brighter coma and longer tails, inviting more frequent astrophotography sessions and sky reports from observatories and enthusiasts alike.
Tips for photographing comet Lemmon
To capture Lemmon’s evolving tail and the occasional disconnection events, consider these practical pointers:
- Use a stable telescope setup (a mid- to long-focus optical system works well) and a sensitive camera to record faint details in the tail.
- Schedule imaging sessions during clear, dark sky conditions far from city lights for maximum contrast against the green coma.
- Employ a time-lapse approach to document tail dynamics, similar to Gilmore’s 60-minute sequence that highlighted the tail’s disconnection.
- In post-processing, align and stack frames to enhance faint features without oversaturating the bright coma.
Where to look and what to expect in October
As Lemmon continues to brighten, observers should track its path through the constellation Leo Minor, near bright stars such as TW Leonis Minoris. The combination of a brightening nucleus and an extended tail makes it a compelling target for astrophotography during October, with the potential for memorable, permanent sky memories.
-FiNding Lemmon and learning more
For those hoping to glimpse Lemmon with the naked eye or through binoculars, check local, up-to-date finder guides and observatory notices. And if you’re interested in creating your own wildlife in the night sky memory, our tips on photographing a comet can help you craft striking long-exposure images that capture Lemmon’s graceful arc across a dark celestial stage.
