On Solar Granulations, Limb Darkening, and Sunspots: Brief Insights in Remembrance of Father Angelo Secchi

Father Angelo Secchi used the existence of solar granulation as a central line of reasoning when he advanced that the Sun was a gaseous body with a photosphere containing incandescent particulate matter (Secchi A. Sulla Struttura della Fotosfera Solare. Bullettino Meteorologico dell'Osservatorio del Collegio Romano, 30 November 1864, v.3(11), 1-3). Secchi saw the granules as condensed matter emitting the photospheric spectrum, while the darkened intergranular lanes conveyed the presence of a gaseous solar interior. Secchi also considered the nature of sunspots and limb darkening. In the context of modern solar models, opacity arguments currently account for the emissive properties of the photosphere. Optical depth is thought to explain limb darkening. Both temperature variations and magnetic fields are invoked to justify the weakened emissivities of sunspots, even though the presence of static magnetic fields in materials is not usually associated with modified emissivity. Conversely, within the context of a liquid metallic hydrogen solar model, the appearance of granules, limb darkening, and sunspots can be elegantly understood through the varying directional emissivity of condensed matter. A single explanation is applicable to all three phenomena. Granular contrast can be directly associated with the generation of limb darkening. Depending on size, granules can be analyzed by considering Kolmogoroff's formulations and Bénard convection, respectively, both of which were observed using incompressible liquids, not gases. Granules follow the 2-dimensional space filling laws of Aboav-Weiner and Lewis. Their adherence to these structural laws provides supportive evidence that the granular surface of the Sun represents elements which can only be constructed from condensed matter. A gaseous Sun cannot be confined to a 2-dimensional framework. Mesogranules, supergranules, and giant cells constitute additional entities which further support the idea of a condensed Sun. With respect to sunspots, the decrease in emissivity with increasing magnetic field strength lends powerful observational support to the idea that these structures are comprised of liquid metallic hydrogen. In this model, the inter-atomic lattice dimensions within sunspots are reduced. This increases the density and metallic character relative to photospheric material, while at the same time decreasing emissivity. Metals are well known to have lowered directional emissivities with respect to non-met