the working group on extrasolar planets of the international astronomical union adopted in 2003 a working definition on the upper limit for what constitutes a planet: not being massive enough to sustain thermonuclear fusion of deuterium. some studies have calculated this to be somewhere around 13 times the mass of jupiter, and therefore objects more massive than this are usually classified as brown dwarfs. some proposed candidate exoplanets were later shown to be massive enough to fall above the threshold, and are likely brown dwarfs, as was the case for: scr 1845-6357 b (12.6 ly), sdss j1416+1348 b (29.7 ly), and wise 1217+1626 b (30 ly).