Was Einstein right about gravity?
The SKA will investigate the nature of gravity and challenge the theory of general relativity. Pulsars, the collapsed spinning cores of dead stars, will be monitored to search for gravitational waves – ripples in the fabric of space-time. The SKA will also use pulsars to test general relativity in extreme conditions, for example close to black holes.
A pulsar is a highly magnetised rotating neutron star – a gigantic nucleus consisting mainly of neutrons with a mass of 1.4 times the mass of the Sun but only as wide as a big city – about 20 km in diameter. A pulsar emits a radio beam along its magnetic axis. As the star rotates it acts like a cosmic lighthouse emitting an apparently pulsed signal when the beam is pointed in our direction. Because a pulsar has a huge amount of mass concentrated in a very small volume, it acts like a massive flywheel in space, and rotates very steadily. The observed pulses act therefore as the ticks of a natural clock which can be as precise as the best atomic clocks on Earth.
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Through its sensitivity, sky and frequency coverage, the SKA will be able to investigate the strong-field realm of gravitational physics by finding and timing pulsars. About 50 years after the discovery of pulsars marked the beginning of a new era in fundamental physics, pulsars observed with the SKA have the potential to transform our understanding of gravitational physics.
Strong-Field Tests of Gravity Using Pulsars and Black Holes – M. Kramer, D. C. Backer,
J. M. Cordes , T. J. W. Lazio, B. W. Stappers, S. Johnston – Science with the Square Kilometre Array, 2004.
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