A pulsar (short for pulsatin radio starn) is a heichly magnetised, rotatin neutron starn that emits a beam o electromagnetic radiation. This radiation can be observed anerly whan the beam o emission is pyntin taewart Yird (muckle lik the wey a lichthoose can be seen anerly whan the licht is pyntit in the direction o an observer), an is responsible for the pulsed appearance o emission. Neutron starns are verra dense, an hae short, regular rotational periods. This produces a verra precise interval atween pulses that range frae milliseiconts tae seiconts for an individual pulsar. Pulsars are believed tae be ane o the candidates for the soorce o ultra-heich-energy cosmic rays (see an a centrifugal mechanism o acceleration).
The precise periods o pulsars mak them verra uisefu tuils. Observations o a pulsar in a binar neutron starn seestem war uised tae indirectly confirm the exeestence o gravitational radiation. The first extrasolar planets war diskivered aroond a pulsar, PSR B1257+12. Certaint teeps o pulsars rival atomic clocks in their accuracy in keepin time.