Solar Rotation Unwrapped: A Thirteen Day Chromospheric Chronicle

The edge of the Sun is never still. In this composite, each horizontal band is the entire solar limb from one observing day, unwrapped from a circle into a straight line so that every prominence around the Sun can be seen side by side. The bright line is the chromosphere, and the flames, arches and spikes rising from it are prominences: vast clouds of cool, dense plasma held aloft in the hot corona by magnetic fields. The thirteen bands span thirteen observing days between 7 December 2025 and 25 February 2026, ten of them from 15 to 25 February. Followed down the stack, individual structures can be traced from day to day. A large arched prominence and a narrow spike appear at nearly the same position on 20 and 21 February, and the arch is still present, changed in shape, on 22 February.

Instrument: HelioSpectra-X spectroheliograph (my own build) on Sky-Watcher EvoStar 72 ED
Camera: ZWO 178MC
Wavelength: H-alpha 656.3 nm

Processing (composite and digitally manipulated):

Limb unwrapping: each day’s full disk image was transformed from polar to linear coordinates around the limb. This changes only the geometry, not the recorded intensities.- using custom python script.
Background: set to a uniform dark grey, faint background haze was removed, and the dim parts of the prominences were gently brightened for visibility - photoshop