College Physics ›› 2018, Vol. 37 ›› Issue (7): 23-24.doi: 10. 16854 /j. cnki. 1000-0712. 170603

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The exact solution to null geodesics at the equatorial plane in Kerr spacetime

ZHAO Fan1,HE Feng2   

  1. 1. Orient Science and Technology College,Hunan Agricultural University,Changsha 410128,China 2. College of Physics and Electronic Science,Hunan University of Science and Technology,Xiangtan 411201,China
  • Online:2018-07-20 Published:2018-07-20

Abstract: The two first integrals of geodesics given by the Euler - Lagrange equations are found at the equatorial plane in Kerr spacetime. Combining the constraint for null geodesics,the orbit differential equation is obtained.The roots of a quartic in integrand are found and reordered. The solution of orbit differential equation can be expressed exactly by the elliptic of the first kind and the third kind.

Key words: Kerr spacetime, null geodesic, exact solution, elliptic integral