Mass of Jupiter

Jupiter is massive enough that the Sun–Jupiter barycentre lies just outside the Sun's surface, so the Sun visibly wobbles: a 12-year, 12 m/s radial-velocity signal that a distant observer could detect, and precisely the method that found 51 Pegasi b in 1995 and opened the exoplanet era. Masses of giant exoplanets are therefore quoted in Jupiter masses as naturally as stellar masses are in solar masses.

It is also as large as a cold body of hydrogen can get: add mass and electron degeneracy pressure makes the planet shrink rather than grow, until around 13 Jupiter masses deuterium fusion begins and the object becomes a brown dwarf. Jupiter's gravity dominates the outer solar system's dynamics, sculpting the asteroid belt's Kirkwood gaps and deflecting or capturing comets: Shoemaker–Levy 9 broke up and struck it in 1994 while the world watched.