PSR B1913 16

PSR 1913 16 (after its discoverers also Hulse -Taylor pulsar or Hulse -Taylor double pulsar, as well as more recent nomenclature also PSR B1913 16 or PSR J1915 1606 ) is a pulsar in the constellation Aquila. It is located at a distance of 21,000 light years. Its rotation period is 59.03 ms, ie about 17 revolutions per second.

Together with another, invisible neutron star, it forms a binary star system. Both stars is the typical mass of a neutron star of 1.4 solar masses ( 1.442 and 1.386 of the pulsar visible the invisible companion ). You run around the common center of gravity in 7.75 h The periastron rotates by 4.2 ° per year, so that - unlike in the diagram - the body do not move on closed ellipses, but on a rosette train ( Apsidendrehung ).

The special significance of this star system is that its discoverers the decreasing orbital period for the first time used for the indirect detection of gravitational waves according to the general theory of relativity, which was later honored with the Nobel Prize for Physics.

Relativistic effects

Russell Alan Hulse and Joseph Taylor discovered the pulsar PSR 1913 16 in 1974 with the Arecibo Observatory. From the observation of periodic time shifts of the pulsar they derived the orbital data of the double star. The orbital motion of the great masses allows to test two predictions of general relativity.

Time dilation

Firstly, Hulse and Taylor showed the time dilation that occurs due to the increase in mass density in the periastron of the two stars: the signal of the pulsar slows down to about 1 microseconds per second ( 10-6).

Gravitational waves

Secondly, the circulation of the body causing a non-spherical displacement of the mass densities, so that the system emits gravitational energy in the form of gravitational waves. It has not yet succeeded in directly detect these gravitational waves.

Hulse and Taylor showed, however, that express the radiation losses in a reduction of the distance of the two stars, which in turn has the consequence that the circulation time is reduced; this results from the conservation of angular momentum or Kepler's third law. In 1984, the loss rate with was - (2.40 ± 0.09) indicated · 10-12 seconds per second. From the discovery of pulsars in 1974 until the publication of data in 1979 took the epoch of periastron from nearly 2 s until 2000, there were almost 30 s

The graph shows the measured values ​​as blue dots; the black line is the prediction of general relativity for the radiation of gravitational energy. Theory and measurements coincide very well.

For this indirect detection of gravitational waves Hulse and Taylor were awarded the 1993 Nobel Prize in Physics.

With the recently Quasar OJ 287 discovered double black hole there is now a second object to which the emission of gravitational waves can be detected indirectly. Here the relativistic effect with a rotation of the orbital ellipse ( Periastrondrehung ) of 39 ° per revolution still many times stronger.