R_🜨

• R_⊕ [a common typographic substitution, as mathematical ⟨⊕⟩ was supported by Unicode a decade before astronomical ⟨🜨⟩]
• The R is not always italic.

• R (radius) and subindex 🜨 (planet Earth).

R_🜨

1. (astronomy) Earth radius: a unit of distance, equal to the radius of the Earth, or 6370 km.

   the transition radius of 2.6 R_🜨 between water worlds and planets with gaseous envelopes

2. (sum of parts) The radius of the Earth specifically.

• R_🜨 may be distinguished from r_🜨, the latter not a unit of measurement but meaning radial distance from the Earth (geocentric distance). Unlike R_🜨, r_🜨 is used relative to our planet specifically.

• (2): R_♁ (R_♁ is apparently uncommon as a comparative unit of measurement)
• (English) R_E