David Kipping, an astrophysicist at the institution, explains that calculating the mass of a star requires its density to be known, as well as the density of an orbiting planet.
With these and measurements of how the gravitational pull of the planet dims the light from the star, obtained using light sensors on Earth, the properties of the two objects can be calculated.
The process is governed in part by Kepler's third law, which states that the square of a planet's orbital duration is proportional to the cube of its distance from the star.
However, the densities of both the star and the planet can only be known with a third object present - a moon orbiting the planet.
"We measure the orbits of the planet around the star and the moon around the planet," says the astrophysicist.
"Then, through Kepler's laws of motion, it's possible to calculate the mass of the star."
