Discovered by Yrjö Väisälä at Turku Observatory in 1938, it was later named after Finnish astronomer Hilkka Rantaseppä-Helenius.
Rantaseppä was discovered on 16 September 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.
Two night later, the body was independently discovered by Belgian astronomer Eugène Delporte at Uccle Observatory.
[b] Lightcurve analysis gave a rotation period of 3.5258 hours with a relatively high brightness variation of 0.41 magnitude, which is indicative of a non-spheroidal shape (U=3).
[4][5] The Collaborative Asteroid Lightcurve Link assumes an albedo for a stony S-type asteroid of 0.24 – derived from 8 Flora, the family's largest member and namesake – and calculates a diameter of 5.93 kilometers with an absolute magnitude of 13.3.