Minimum required mean density of the orbiting body as a function of its orbital period—described by Equation (1). The typical density ranges for comets (0.3–0.6 g cm⁻³), asteroids (1.0–3.5 g cm⁻³), and terrestrial planets (4.0–5.5 g cm⁻³) are indicated on the left-hand side. The dotted–dashed and dotted curves are approximate modifications to Equation (1) multiplied by a factor of (1 − e)^−3/2 for eccentricities of 0.1 and 0.2, respectively, which illustrate how higher eccentricities at fixed periods push the required density higher. Vertical red lines mark the two periods identified in ZTF J0328−1219, while the vertical blue line is a characteristic period of WD 1145+017.