Typically, neutron stars are about 20 km in diameter and have around the same mass as our sun. what is a typical neutron star density in g/cm3?

4.7 × 10¹⁴ g/cm³

Explanation:

The mass of the sun (and of the neutron star) is 1.98 × 10³⁰ kg = 1.98 × 10³³ g.

The diameter of the neutron star is 20 km and its radius is 1/2 × 20 km = 10 km = 10⁴ m = 10⁶ cm

If we consider the neutron star to be approximately spherical, we can calculate its volume using the following expression.

V = 4/3 × π × r³

V = 4/3 × π × (10⁶ cm)³

V = 4.19 × 10¹⁸ cm³

The density (ρ) is equal to the quotient between the mass and the volume.

ρ = 1.98 × 10³³ g / 4.19 × 10¹⁸ cm³ = 4.73 × 10¹⁴ g/cm³ ≈ 4.7 × 10¹⁴ g/cm³