Precession of the pericenter

In Astronomy, the precession of the pericenter is the phenomenon according to which a body in orbit around an other (for example a Planet around a star) sees the ellipse describing its trajectory to turn slowly in the orbital plan of the object. That results in the fact that during the successive revolutions of the object, the direction described by the line passing by the central body and the body orbits about it at the time (the Périastre) is not fixed, but varies slowly.

The precession of the pericenter can be due to many causes. It can inter alia occurring:

if the central body with spherical symmetry but is not slightly flattened, the gravitational Potentiel generated by the central body does not decrease exactly like that of a spherical body with the distance, causing a precession;
so of other bodies orbits around the central body, the gravitational force exerted on the body in orbit can lead it to present the phenomenon of precession of the pericenter;
because of variation to the Keplerian Movement resulting from the General relativity.

In the Solar system, it is the planet Mercure which knows the most important precession of the pericenter, about 550 seconds of arc by Siècle. The largest part of this precession is due to the disturbances caused by another planets of the solar system, in particular Venus and Jupiter. There exists however a residual precession of 43" /siècle, known as of second half of the 19th century. It has a time planned to explain it by a light flatness of the Sun, but this assumption had to be abandoned, the direct observation of this one not showing sufficient flatness to be able to cause such a precession. It is finally Albert Einstein which explained fine 1915 this precession residual of the Mercury perihelion within the framework of the very new general theory of relativity that it had just discovered. It was besides the first confrontation of general relativity to the observation.

The relativistic precession of the pericenter is an example of post-Keplerian Paramètre. For the binary Pulsar PSR B1913+16, it is about 4 degrees per annum, and half less for PSR B1534+12. For the Pulsar doubles PSR J0737-3039, it reaches the 16 degrees per annum.

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