↩ 🔵 🔵 🔵 ❪✺❫ Astronomical Concepts ○ ❪✺₄❫ Physical Sets ○ ❪✺₄❫ High-Energy Astrophysics Sets ○ ❪✺_ₛₛ❫ Astronomical Subsets ○ ❪∈₂❫ Astronomical Sets ○ ❪◑❫ Astronomical Objects ○ ❪◑❫ Constellations ○ ❪◑❫ Surveys ○ ❪◑❫ Telemetry Networks ○