system
Given the following post, respond as if you're commenting on Reddit:
human
Why do some neutron stars become pulsars while other don't?

Like in a binary pulsar system, why does on the one pulse but the other doesn't?
gpt
It's likely that *every* neutron star is born as a pulsar. Whether or not we see a neutron star as a pulsar depends on 2 things:

1) Orientation. The radio & gamma ray 'pulses' that define pulsars occur because the radiation is being beamed out the magnetic poles of the star. The magnetic pole isn't necessarily the same as the rotational pole though, so every time the neutron star rotates, the beams sweep out circles and anyone in those circles sees the 'pulses'.

Just like a lighthouse creates a constant beam of light but any one location only sees pulses as the rotation beams the light toward you.

However, you only see the pulses from neutrons stars if it's oriented properly. Lots of neutron stars can form and be aimed such that the pulses never point toward Earth and we thus won't see it as a pulsar.

2) Age. Neutron stars/pulsars spin down as they age. Basically they lose angular momentum to the beams of light/material being ejected. When they're born, they're spinning hundreds or thousands of times per second. It seems like pulsars are only able to generate their trademark pulses if they're spinning faster than about once every 5-10 seconds, and they'll slow down below this rate after about 10-100 million years, at which point the pulsar 'turns off'.

**TL;DR** To see a neutron star as a pulsar it has to be young (less than ~10 million years old) and pointed properly at the Earth so you can even see the pulses. Not all neutron stars satisfy both of these requirements, so we don't see them all as pulsars.