The Team was hunting specifically for evidence of frame dragging in these extreme objects, where the white dwarf’s spinning literally drags space-time along with it, like dragging water along your body as you spin in a pool. General relativity predicts that this effect would manifest itself as extra precession, or the rotating of the orbit’s axis — imagine both stars were on the sides of a spinning top, and the top beginning to wobble; that’s precession.
Based on observations of the arrival time of the pulsar signal, the orientation of the orbit, and how the orbit varied, the researchers determined that the precession matched what would be expected if there was a contribution from the white dwarf dragging space-time along with it. The white dwarf has to be spinning very fast, once per seconds or less, according to the paper published yesterday in Science.
The paper’s authors wrote in an article for the conversation
that such a system might have formed from a pair of stars that died. The first, more massive star would have become the white dwarf and begun sucking mass from the second star, creating a disk and eventually bestowing it with a quick spin. The second star eventually exploded as a supernova, leaving behind the pulsar the researchers used to perform this measurement.
( ) Einstein’s
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