Discovered in January 2025, comet Lemmon, or C/2025 A6 (Lemmon), became visible to the naked eye in autumn 2025 as it made its closest approach to Earth.
Comet’s spend most of their time in ‘quiet mode’ in the outer reaches of the Solar System, only waking up as they come closer to the Sun. The Sun causes the ice on their surfaces to turn from solid to gas, making the comet brighten in the night sky.
This image, taken by amateur astrophotographer Ela Şen, clearly reveals in green the halo of gas surrounding comet Lemmon’s tiny nucleus. This halo is known as the coma. Material from the coma gets swept into a tail, which we see in cyan. The tail gets larger as the comet approaches the Sun.
Find out more about the structure of a comet here.
In the background, just to the right of the comet, we see NGC 3184, or the ‘Little Pinwheel Galaxy’, a beautiful spiral galaxy nearly 40 million light-years away.
Technical details:
The frame combines comet-aligned and star-aligned integrations to reveal both the tail structure and a clean star field with the galaxy.
- Image taken on 6 October 2025 in Çanakkale, Turkey
- Optics: William Optics GT71 mm telescope, zwo asi 294 Mc pro colour camera.
- Mount/Guiding: Celestron AVX, ASIAIR
- Integration: Light frames: 9×130 seconds, Dark frames: 7×130 seconds, Flat frames: 12×1.0 seconds
- Processing: The image was only stacked, integrated and processed in Pixinsight; PixInsight WBPP; CometAlignment; star field stacked separately; recombination via Screen/PixelMath; mild colour calibration (SPCC), gradient removal (GraXpert), noise reduction; gentle curves/saturation. (Composite disclosed as comet+stars recombination.)
[Image description: A bright green comet with a glowing core streaks across a dark star-filled sky. The comet’s tail is long and wispy, fading into shades of blue as it trails off into the distance. Surrounding the comet are countless tiny white stars, with a few larger stars and a faint, spiral galaxy visible nearby to the right of the comet.]