Average density (ρ _⋆) of Pop III stars with Z = 10⁻⁵ (red solid line) and Z = 10⁻⁹ (red dashed line) in the mass range of 30–300M _⊙ compared to Pop I stars (black solid line) in the mass range of 0.1–300M _⊙. All stars are in their main-sequence stages. Pop III stars typically have ρ _⋆ ∼ 0.01–1 ρ _⊙ and those with lower metallicities or lower masses are denser. The stellar density of 1ρ _⊙, 0.1ρ _⊙, and 0.01ρ _⊙ are marked with green dotted lines.