Positronium is a short-lived ( 10⁻⁹ ~s ) bound state of an electron and a positron (a positively charged particle with mass and charge equal (in magnitude) to an electron) revolving round their common centre of mass. If E ₀, v ₀ and a ₀ are respectively the ground state energy, the orbital speed of electron in first orbit and the radius of the first ( n=1 ) Bohr orbit for Hydrogen atom, the corresponding quantities E