During observations by Instituto de Astrofísica de Canarias in Tenerife, Spain in 1998, a substellar-mass object was discovered to orbit approximately 300 astronomical units (AU) from the star.
During the Extreme Solar Systems conference held on June 25–29, 2007, in Santorini, Greece, Reffert et al. announced the detection of two substellar objects orbiting Iota Aurigae in 2:1 resonance.
Using the radial velocity technique, the search for substellar companions has thus far failed to find a brown dwarf or extrasolar planet in the "hot zone" orbit around Kappa1 Ceti.
Assuming that a substellar object has a composition similar to the Sun's and at least the mass of Jupiter (approximately 10−3 solar masses), its radius will be comparable to that of Jupiter (approximately 0.1 solar radii).