An ALMA large program is currently studying how anomalously top-heavy distributions of this quantity may arise from a related distribution for cores. Codes like MESA express the equation of hydrostatic equilibrium in terms of this Lagrangian coordinate. For a polytrope, this quantity is proportional to the “3 minus n over 1 minus n” power of radius. This quantity’s PDF was approximated as a power law with an exponent of minus 2.35 by Edwin Salpeter; that distribution is this quantity’s (15[1])(*) “initial function.” (10[1])A main sequence star’s luminosity is roughly proportional to the seven-halves power of this quantity. (10[1])A star’s initial value of this quantity determines whether it will become a white dwarf, neutron star, or black hole. For 10 points, Type 1a supernovae occur when a white dwarf’s value of what quantity exceeds the Chandrasekhar limit? ■END■