How to weigh a distant star ?

Till date computer models have been used to approximate the mass of a distant star. Now astrophysicist at the Harvard-smithsonian centre for asstrophysics in cambridge, UK, claim to have developed a new method for weighing a distant star. We know there are ten to the power 23 stars (almost a million million million million stars) in the observable universe. Many of them have a family (star system) like our solar system.

If a star has a planet and the planet has a satellite, let them cross in front of the parent star. This passage enables the scientists to estimate not only their sizes but orbits too.And this knowledge gives the mass of the star .Other methods for weighing the stars are also available .