Messier 51 – The Whirlpool Galaxy

Messier 51, the Whirlpool Galaxy, is a face-on grand-design spiral in Canes Venatici, about 31 million light-years away. It is one of the sky’s clearest examples of galactic interaction: its smaller companion, NGC 5195, is tugging gravitationally on one of its arms, and that encounter is exactly what sharpens its spiral structure and drives star formation along the arms. A tidal bridge of gas and dust connects the two galaxies.

Captured over three nights (19, 20 and 21 May 2026) from my Bortle 7 backyard in San Pedro de Alcántara, Málaga, Spain. The base is broadband: 180 × 180 s through an Optolong L-Pro filter — 9 hours — carrying the resolution, the blue-white disk and the faint outer structure. To that I added 55 × 300 s with an L-eNhance dual-band filter (4 h 35 min), used to extract the Hα signal from the star-forming regions. Roughly 13 h 35 min in total.

The spiral structure is well defined, with dust lanes discernible within the disk and the wound arms holding good contrast. NGC 5195 resolves above with its own dust lane and the halo distorted by the interaction, and the tidal bridge linking it to M51 gains clear presence at this integration. The HII regions — pink knots scattered along the arms, where new stars glow in Hα — appear where they should, without tinting the stars or the background. Stars stay small and controlled out to the corners. The Hα contribution in a galaxy is subtle rather than transformative: it reinforces localized areas, not the whole frame the way it would in an emission nebula.