Kepler-33
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Kepler-33 is a star about in the constellation of Cygnus, with a system of five known planets. Having just begun to evolve off from the
main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...
, its radius and mass are difficult to ascertain, although data available in 2020 shows its best-fit mass of 1.3 and radius of 1.6 are compatible with a model of a
subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...
star.


Planetary system

The first detections of the candidate four-body planetary system were reported in February 2011. On January 26, 2012, the planetary system around the star was confirmed, including a fifth planet. However, unlike some other planets confirmed via Kepler, their masses were initially not known, as
Doppler spectroscopy Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in ...
measurements were not done before the announcement. Judging by their radii, b may be a large
super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...
or small
hot Neptune A hot Neptune is a type of giant planet with a mass similar to that of Neptune or Uranus orbiting close to its star, normally within less than 1 AU. The first hot Neptune to be discovered with certainty was Gliese 436 b (Awohali) in 2007, an ex ...
while the other four are all likely to be the latter. , the masses of planets e & f have been measured, with upper limits on the masses of planets c & d. These mass measurements confirm Kepler-33 d, e & f to be low-density, gaseous planets. 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 its current configuration is highly susceptible to perturbations, therefore assuming stability, no additional giant planets can be located within 30 AU from the parent star.


See also

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55 Cancri 55 Cancri is a binary star system located 41 light-years away from the Sun in the zodiac constellation of Cancer. It has the Bayer designation Rho1 Cancri (ρ1 Cancri); ''55 Cancri'' is the Flamsteed designation (abbrev ...
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Kepler-11 Kepler-11, also designated as 2MASS J19482762+4154328, is a Sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,110 light years from Earth. It is located within the field of vision of the Kepler spa ...
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Kepler-20 Kepler-20 is a star about from Earth in the constellation Lyra with a system of at least five, and possibly six, known planets. The apparent magnitude of this star is 12.51, so it cannot be seen with the unaided eye. Viewing it requires ...


References

Cygnus (constellation) G-type subgiants 707 Planetary transit variables Planetary systems with five confirmed planets J19161861+4600187 {{Main-star-stub