Firstly I thought that Pulsars are rapidly rotating, highly magnetic compact stars. The rotating magnetic field of a pulsar acts as a generator, accelerating energetic charged particles that then stream along the field lines”. At a glance the answer looks quite decent but second look does not convinces me. First important thing how are these magnetic fields are formed? For a electrically charged particles moving in a ring generates a magnetic field but the particles in neutron stars are neutrons which are electrically neutral. Then a second one was the equations which are involved in it, when protons collide with electrons during the formation of neutron star they form neutrons and give out neutrino, to what I have learnt, the equation does not feels good as when a neutron gets converted into a proton by beta decay an electron and an anti-neutrino is emitted so if we reverse this in time a proton, electron and anti-neutrino forms a neutron which is different from the previous equation, why are there two sets of equations for this?


1 Answer 1


welcome in the stack-community. Here are my proposed answers:

$\mathrm{I}.$ A pulsar is a neutron star that is mostly made up of neutrons. On the surface, gravitational pressure does not hinder the $\beta^{-}$ decay of neutrons, and so charged particles such as electrons and protons can form a magnetic field due to the whirling rotation of these objects. The small size and the high angular momentum create enormous magnetic fields capable of "tapering" the atoms.

$\mathrm{II.}$ It is not correct to say that electrons collide on protons, during the gravitational collapse. More precisely, due to the gravitational pressure, a $\beta$-inverse decay is triggered, which can be written as: $$ \bar{\nu}_{e} + p \rightarrow n + e^+$$ i.e. electronic anti-neutrino, $\bar{\nu}_e$, and a proton, p, exchange a $W^+$ virtual boson, and produce a neutron plus a positron. This positrons then collide with the free elctrons in the star during the collapsing and emits photons: $$e^-+e^+\rightarrow 2\gamma$$

P.s. Thanks to @Triatticus for the corrections to the photons counting in the electron-positron annihilation.

  • 1
    $\begingroup$ Should be $e^+ + e^- \rightarrow \gamma + \gamma$ $\endgroup$
    – Triatticus
    Commented Jan 13, 2021 at 18:29
  • $\begingroup$ Yes @Triatticus, you are right. Just a bad typo, i'll edit. $\endgroup$ Commented Jan 13, 2021 at 19:11
  • $\begingroup$ Thank you so much sir. $\endgroup$
    Commented Jan 14, 2021 at 3:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.