Investigation of the periastron shift of star orbit in Hernquist potential

Abstract

Abstract Understanding of the dynamics of stars around a strong gravitational body such as a supermassive black hole at the centre of galaxies is still incomplete. There is strong evidence suggesting that the orbits of stars in the galactic centre do not follow the Kepler’s laws. In this work, we study the periastron shift from the classical gravitational effect. We select the Hernquist potential function representing a galactic component to examine the rate of change of periastron angular position of a test star. We employ the numerical method to track the orbital dynamics of the test star in that potential. First of all, the periastron shift of the test star is noted and it evolves in the retrograde way. We find that the precession rate varies considerably with the initial speed of the star. In conclusion, we speculate that this effect is non-negligible and it should be accounted when considering the motion of stars in the galactic centre.