It is known that ground states of the pseudo-relativistic Boson stars exist if and only if the stellar mass N > 0 satisfies N < N * , where the finite constant N * is called the critical stellar mass. Lieb and Yau conjecture in [Comm. Math. Phys., 1987] that ground states of the pseudo-relativistic Boson stars are unique for each N < N * . In this paper, we prove that the above uniqueness conjecture holds for the particular case where N > 0 is small enough.By making full use of (1.3), Lenzmann in [26] established the following interesting existence and analytical characters of minimizers for e(N ):Theorem A ([26, Theorem 1]) Under the assumption m > 0, the following results hold for e(N ):1. e(N ) has minimizers if and only if 0 < N < N * , where the finite constant N * is independent of m.
Any minimizer3. Any nonnegative minimizer of e(N ) must be strictly positive and radially symmetricdecreasing, up to phase and translation.We remark that the existence of the critical constant N * > 0 stated in Theorem A, which is called the critical stellar mass of boson stars, was proved earlier in [14,29]. Further, the dynamics and some other analytic properties of minimizers for e(N ) were also investigated by Lenzmann and his collaborators in [12,13,14,15,25,26] and references therein. Stimulated by [20,22], the related limit behavior of minimizers for e(N ) as N ր N * were studied more recently in [23,33,37], where the Gagliardo-Nirenberg type inequality (1.3) also played an important role. Note also from the variational theory that any minimizer u of e(N ) satisfies the Euler-Lagrange equation −∆ + m 2 − m u − 1 |x| * |u| 2 u = −µu in R 3 , (1.5)