The discovery of the first extra-Solar system planet was made by Wolszczan and Frail (1992). Precise measurements of the radio pulses from the 6.2ms pulsar PSR1257+12 showed systematic variations in the arrival times of the pulses. The regular and predictable variations in the pulse arrival times inferred to those authors that the neutron star is orbited by two planet-sized bodies of masses of at least 2.8 and 3.4 times the mass of the Earth. The initial data suggested also the presence of at least one additional planet whose existence has been confirmed by Wolszczan (1994).

Because neutron stars are formed through a supernova explosion, it is not obvious how these planets came to be in orbit around the pulsar. If they formed before the supernova event, how did they manage to survive the explosion? Could they have been formed out of debris from the shattered star? Could they have been captured from another star?

Check out Alex Wolszczan's page on planets around pulsars

Suggested readings:

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