Binary pulsar
= Binary pulsar
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A binary pulsar is a <pulsar> in a <binary star>: the companion's <gravity> changes the emitting <neutron star>'s motion and hence its pulse arrival times. The companion need not itself be a detectable <pulsar>. <Pulsar timing> turns that motion into a measurable <orbit>, making the system useful for <stellar mass determination> and tests of <general relativity>.