A unit of mass, now being used in astronomy to express the masses of new planets being discovered in orbit around various stars. It's equal to the mass of the planet Jupiter, estimated to be about 1.899 x 1024 metric tons, or, if you please, 1.899 yottatonnes (Yt). By coincidence, this is approximately 0.001 Sun (0.000 955 Sun, to be more exact); it is also about 317.7 times the mass of the Earth