↩ 🔵 🔵 🔵 ❪✺₄❫ Astronomical Sets ○ ❪✺_❫ Astronomical Subs ○ ❪✺_ₛₛ❫ Physical Subsets ○ ❪✺_ₛₛ❫ High-Energy Astrophysics Subsets ○ ❪✺_ₜₛ❫ Astronomical Typesets ○ ❪◑❫ Galaxies ○ ❪◑❫ Galaxy Clusters ○ ❪◑❫ Nebulae ○ ❪◑❫ Novae ○ ❪◑❫ Star Systems ○ ❪◑❫ Supernova Remnants ○ ❪◑❫ White Dwarves ○ ❪◔❫ Standard Epochs ○