The Sun

A living model built on the laws of physics, from the granules on the surface to the corona

A cycle lasts about 11 years. The dot is where we are now; the year can be changed in the settings.

Colour — the Planck spectrum, turned into a colour with the CIE 1931 eye-sensitivity curves. No tinting.
The dark limb — Eddington’s model atmosphere: near the edge we see a higher, cooler layer.T⁴ = ¾ T⁴eff (τ + ⅔)
Rotation — the equator turns in 25 days, the poles in 35 (Snodgrass & Ulrich 1990).Ω = 14.713 − 2.396 sin²φ − 1.787 sin⁴φ °/day
Where sunspots appear — around 30° latitude early in the cycle, closer to the equator towards its end (Spörer’s law).
The magnetic polarity of sunspot pairs is opposite in the two hemispheres and flips every cycle (Hale’s law). The farther from the equator, the more the pairs are tilted (Joy’s law).
Coronal density — after Baumbach and Allen; the field is a dipole with a source surface at 2.5 solar radii.nₑ = 10⁸ (2.99 r⁻¹⁶ + 1.55 r⁻⁶) cm⁻³
Flares — frequency and strength follow a power law; each event follows the standard model: the flux rope erupts, the field reconnects, an arcade of hot loops forms.

It won’t start