A contribution of quantum vacuum to the energy momentum tensor is inevitably experienced in the present universe. One requires the presence of non-zero cosmological constant ($\Lambda$) to make the various observations consistent. A case of $\Lambda$ in the Schwarzschild de Sitter space-time shows that precession of perihelion orbit provides a sensative solar test for non-zero $\Lambda$. Application of the relations involving $\Lambda$ to the planetery perturbation indicates the values near to the present bound on $\Lambda$. Also suggested are some relations in vacuum dominated flat universe with a positive $\Lambda$.