[5] The discovery of four planets orbiting the star was announced October 2012 by analyzing data gathered by Kepler space telescope.
[3] Follow-up radial velocity measurements confirmed the existence of Kepler-89d, indicating that Kepler-89d is slightly larger and more massive than Saturn.
[6] In October 2013, other three planets were confirmed with Kepler-89c and Kepler-89e getting reasonable mass constraints.
This was the first time a planet-planet transit in front of the star was detected.
[7] Stephen R. Kane did a dynamical analysis of the Kepler-89 system that demonstrated that planets c and d, although close to the 2:1 secular resonance, are not permanently in a 2:1 resonance configuration.