Draugr is the least massive known exoplanet with a precisely determined mass, measuring about 0.020 Earth masses. It is also designated PSR B1257+12 b, or PSR B1257+12 A.
Draugr orbits the pulsar PSR B1257+12, now commonly called Lich, roughly 2,300 light-years away in the constellation Virgo. The planet was discovered through pulsar timing: astronomers measured tiny, regular changes in the pulsar's arrival times caused by the planet's gravitational pull. It was announced in 1994 as part of the first confirmed planetary system beyond the Solar System.
At around twice the Moon's mass, Draugr is far smaller than Earth. Its host is a rapidly rotating neutron star—the dense remnant of a stellar explosion—so its environment would be extremely hostile. The planet completes an orbit in about 25.3 days at a distance of roughly 0.19 AU.
The name Draugr was awarded through the International Astronomical Union's NameExoWorlds campaign in 2015 and refers to an undead being in Norse mythology. Kepler-37b is smaller in radius, but that does not make it less massive; size and mass are different records.