How astronomers measure a planet's mass?

Steemians ! Surely, you ,d like to know how astronomers measure a planet's mass? It is the gravity of aplanet through which they can meaure the planet,s mass. The most commonly used technique is to observe a body orbiting or passing close to the planet and see how its path is affected by the planet's gravity. When the moon is orbiting a planet at certain distance from planet, the orbital period of the moon will mainly depend on the planet's mass. The more massive the planet, the more strongly it attracts the moon and faster the moon moves. It is straightforward for astronomers to calculate the planet's mass after we have observed the motion of one of its moons for a while. [Source] (http://curious.astro.cornell.edu/about-us/57-our-solar-system/planets-and-dwarf-planets/orbits/245