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  • 1801.03874

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The K2-138 system: a near-resonant chain of five sub-neptune planets discovered by citizen scientists

Research output: Contribution to journalJournal articlepeer-review

  • Jessie L. Christiansen
  • Ian J. M. Crossfield
  • Geert Barentsen
  • Chris J. Lintott
  • Thomas Barclay
  • Erik Petigura
  • Joshua E. Schlieder
  • Courtney D. Dressing
  • Andrew Vanderburg
  • Campbell Allen
  • Adam Mcmaster
  • Grant Miller
  • Martin Veldthuis
  • Sarah Allen
  • Zach Wolfenbarger
  • Brian Cox
  • Julia Zemiro
  • Andrew W. Howard
  • John Livingston
  • Evan Sinukoff
  • Timothy Catron
  • Andrew Grey
  • Joshua J. E. Kusch
  • Ivan Terentev
  • Martin Vales
  • Martti H. Kristiansen
Article number57
<mark>Journal publication date</mark>1/02/2018
<mark>Journal</mark>The Astronomical Journal
Issue number2
Number of pages9
Publication StatusPublished
<mark>Original language</mark>English


K2-138 is a moderately bright (V = 12.2, K = 10.3) main-sequence K star observed in Campaign 12 of the NASA K2 mission. It hosts five small (1.6–3.3 ${R}_{\oplus }$) transiting planets in a compact architecture. The periods of the five planets are 2.35, 3.56, 5.40, 8.26, and 12.76 days, forming an unbroken chain of near 3:2 resonances. Although we do not detect the predicted 2–5 minute transit timing variations (TTVs) with the K2 timing precision, they may be observable by higher-cadence observations with, for example, Spitzer or CHEOPS. The planets are amenable to mass measurement by precision radial velocity measurements, and therefore K2-138 could represent a new benchmark system for comparing radial velocity and TTV masses. K2-138 is the first exoplanet discovery by citizen scientists participating in the Exoplanet Explorers project on the Zooniverse platform.

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This is an author-created, un-copyedited version of an article accepted for publication/published in The Astronomical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it