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an open source database of all discovered extrasolar planets

EPIC 206011691

The planetary system EPIC 206011691 hosts at least 2 planets.

  System parameters
Primary system name EPIC 206011691
Alternative system names EPIC-206011691, K2-21
Right ascension 22 41 12.89
Declination -14 29 20.35
Distance [parsec] 65±6edit
Distance [lightyears] 212±20
Number of stars in system 1
Number of planets in system 2

ArchitectureArchitecture of the system

This list shows all planetary and stellar components in the system. It gives a quick overview of the hierarchical architecture.

  •  EPIC 206011691, stellar object
    •  EPIC 206011691 b, planet, semi-major axis: 0.073+0.006−0.007 AU
      •  EPIC 206011691 c, planet, semi-major axis: 0.103+0.008−0.009 AU

      PlanetsPlanets in the system

      This table lists all planets in the system EPIC 206011691.

        EPIC 206011691 b EPIC 206011691 c
      Alternative planet names 2MASS J22411288-1429202 b, K2-21 b 2MASS J22411288-1429202 c, K2-21 c
      Description The EPIC 206011691 system consists of a pair of small planets orbiting a nearby M0 dwarf close to the 5:3 resonance.edit The EPIC 206011691 system consists of a pair of small planets orbiting a nearby M0 dwarf close to the 5:3 resonance.edit
      Lists Confirmed planets
      Mass [Mjup] N/A N/A
      Mass [Mearth] N/A N/A
      Radius [Rjup] 0.14±0.04edit 0.17±0.05edit
      Radius [Rearth] 1.6±0.4 1.9±0.5
      Orbital period [days] 9.3241±0.0006edit 15.5012+0.0009−0.0010edit
      Semi-major axis [AU] 0.073+0.006−0.007edit 0.103+0.008−0.009edit
      Eccentricity N/A N/A
      Equilibrium temperature [K] N/A N/A
      Discovery method transit
      Discovery year 2015
      Last updated [yy/mm/dd] 15/07/31

      starStars in the system

      This table lists all stars in the system EPIC 206011691.

        EPIC 206011691
      Alternative star names K2-21, 2MASS J22411288-1429202
      Mass [MSun] 0.64±0.11edit
      Radius [RSun] 0.60±0.10edit
      Age [Gyr] > 1.0000edit
      Metallicity [Fe/H] -0.11±0.13edit
      Temperature [K] 4043±375edit
      Spectral type M0V
      Visual magnitude 12.85±0.02edit

      Planet sizes

      The following plot shows the approximate sizes of the planets in this system The Solar System planets are shown as a comparison. Note that unless the radius has been determined through a transit observation, this is only an approximation (see Lissauer et al. 2011b).

      PlutoMercuryMarsVenusEarthNeptuneUranusSaturnJupiterEPIC 206011691 bEPIC 206011691 c

      Habitable zone

      The following plot shows the approximate location of the planets in this system with respect to the habitable zone (green) and the size of the star (red). This is only an estimate, using the star's spectral type and mass. Note that if no green band is shown in the plot, then the planet's orbit is far outside the habitable zone. The equations of Selsis, Kasting et al are used to draw the inner and outer boundaries.

      EPIC 206011691 bEPIC 206011691 c

      referencesScientific references and contributors

      Links to scientific papers and other data sources


      This table lists all links which are relevant to this particular system. Note that this is just a summary. More references to the scientific publications and comments can be found in the commit messages. To see these, head over the github or click here to directly go to the git blame output of this system. In the left column of the output you can see the commit message corresponding to each parameter. It also lists the date of the last commit and the person making the changes. Within the commit message, you will find a link to the scientific publication where the data is taken from. Note that this is a new feature and not all system parameters might have a reference associated with it yet. Please help making this catalogue better and contribute data or references!

      Open Exoplanet Catalogue contributors

      Contributor E-mail Number of commits
      Andrew Tribick ajtribick(at) 4
      Hanno Rein hanno(at) 1
      Ryan Varley ryanjvarley(at) 1

      This table lists all people who have contributed to the Open Exoplanet Catalogue. Please consider contributing! Click here to find out how. You can also view all commits contributing to this file on github.

      xmlData download

      You can download the xml file corresponding to this planetary system, which is part of the Open Exoplanet Catalogue. All information on this page has been directly generated from this XML file. You can also download the entire catalogue over at github. If you prefer to download the dataset as an ASCII tables, you might find the oec_tables repository usefule.


      If you spot an error or if you can contribute additional data to this entry, please send an e-mail to Please include the corrected xml file and a reference to where the new data is coming from, ideally a scientific paper. If you are fluent with git and github, you can also create a pull request or open an issue on the Open Exoplanet Catalogue repository. Please include the reference to the relevant scientific paper in your commit message.