OGLE-2016-BLG-1928 is a rogue terrestrial-mass extrasolar planet which does not orbit any type of star. It was discovered by a microlensing event that only lasted for 41 minutes. It is the shortest timescale microlensing event ever found.[1]
The planet should have a mass of about 0.3 to 1.0 Earth mass[2] based on current planet-formation theories about ejected planets, around the same as Mars or Earth.