Age of Pulsars
Ratio (time) is known as ‘age’ of pulsar
In reality, may be longer than the real age.
Pulsar characteristic lifetime ~ 10 years
Total no observable pulsars ~ 5 x 10
Notes:
The ratio P/Pdot has the dimension of time and is often referred to as the age of the pulsar (assuming it was formed with a rotation period of a few millisec). For the Crab and Vela pulsars, the determination of the age of the pulsars was instrumental in associating the pulsar with the SNR.
In reality, P/Pdot may be significantly longer than the real age because pulsars are not perfect rotating magnetic dipoles, their magnetic fields decay and Pdot was larger in the past. The Crab Nebula is about 3000 years old.
Most pulsars are thought to have a characteristic lifetime of about 10 million years.
Integrating the distributions of pulsars observed in relatively small regions of the sky over the whole of the Galaxy, we find that there are about 50,000 observable pulsars (in the Galaxy). This is a minimum number: there may be many more at fainter luminosities and we also have to correct for beaming factors (which brings this number up to about 200,000.