Kepler-33

Kepler-33 is a star in the constellation of Cygnus with a system of five known planets. Having just begun to evolve off from the main sequence,^[6] its radius and mass are difficult to ascertain, although data available in 2020 shows its best-fit mass of 1.3M_☉ and diameter of 1.6R_☉ are compatible with a model of a subgiant star.^[2]

Planetary system[]

First detections of the four-body planetary system were reported in February 2011.^[7] On January 26, 2012, a 5th planet around the star was confirmed.^[6] However, unlike other planets confirmed via Kepler, their masses were initially not known, as Doppler Spectroscopy measurements were not done before the announcement. Judging by their radii, b may be a large Super-Earth or small Hot Neptune while the other four are all likely to be the latter.

Planets b and c may actually be in a 7:3 resonance, as there is a 0.05 day discrepancy; there is also a small 0.18 day discrepancy between a 5:3 resonance between planets c and d. The other planets do not seem to be in any resonances, though near resonances are 3d:2e and 4e:3f.

The planetary system in current configuration is highly susceptible to perturbations, therefore assuming stability, no additional giant planets can be located within 30 AU from the parent star.^[8]