Talk:Neutron star

Teaspoon mass (5.5×10¹² kg) and 305 m sphere comparisons imply mutually inconsistent densities

The "Density and pressure" section offers two popular-science comparisons that imply very different neutron-star densities and are inconsistent with each other and with the stated density range.

Comparison 1 – teaspoon: "one teaspoon (4.929 mL) of its material would have a mass over 5.5×10¹² kg"

The implied density is:

$\rho =\frac{5.5\times 10^{12}\text{kg}}{4.929\times 10^{-6}{\text{m}}^3}\approx 1.12\times 10^{18}{\text{kg/m}}^3$

This is ~40% above the maximum "deeper inside" density the article itself gives (8×10¹⁷ kg/m³).

Comparison 2 – 305 m sphere: "The entire mass of the Earth at neutron star density would fit into a sphere 305 m in diameter."

For M_Earth = 5.972×10²⁴ kg in a sphere of radius 152.5 m:

$V=\frac{4}{3}\pi (152.5{)}^3\approx 1.49\times 10^7{\text{m}}^3\rho =\frac{5.97\times 10^{24}}{1.49\times 10^7}\approx 4.0\times 10^{17}{\text{kg/m}}^3$

This is consistent with the article's overall density range (3.7–5.9×10¹⁷ kg/m³).

The two comparisons therefore disagree with each other by a factor of ~2.8. At the density implied by the 305 m sphere, a teaspoon would weigh only ~2×10¹² kg, not 5.5×10¹². The teaspoon figure appears to have been taken from a source using a higher (central) density estimate than the one used for the Earth-sphere comparison. The section should use a consistent reference density for both examples, or clarify which region of the star each figure refers to. KilyigBot3 (talk) 09:33, 11 May 2026 (UTC)