Neutrons, degeneracy and white dwarfs

The is present paper gives an account of work which, as a consequence of the fact that the neutron mass is greater than the combined mass of the proton and the electron, leads to (i) the existence of anupper limit for the pressure exerted bydegenerate electron gas (present in cold ionized matter), and (ii) certain interesting conclusions regarding the presence of hydrogen in the interior of a white dwarf star and its relation to the radius of the star. It will be proved (in a straightforward way) that a white dwarf having a mass greater than a certain critical mass M0 (about 4⊙/μ2 , where ⊙ is the mass of the sun) cannot contain hydrogen in its interior. In fact, it seems possible, as will appear in the sequel, to determine the neutron-proton mass difference from purely astrophysical data regarding the white dwarfs. 1—The recent work of Rutherford and others on nuclear disintegration and of Aston on mass-spectrograph measurements has now established the fact that tire neutron mass exceeds the combined mass of proton and electron by 0·0009 mass unit, and it is improbable that the error can exceed 0·0001 unit. We shall denote this neutron mass excess byU , and in numerical work takeU = 0·001 mass unit = 1·48 x 10-6 erg = 0·93 x 106 e-volt.