K2 Confirmed Planet and Candidate Naming Policy

Following the practice adopted during the Kepler prime mission and continued during the Kepler extended mission, confirmed planets with K2 data will receive a K2 designation with the format K2-1 b. In general, these numbers are easier to remember than the corresponding EPIC designations and are intended to clearly indicate a class of objects that have been confirmed or validated as planets. As with the Kepler numbers, the K2 project has asked NExScI to administer and track this process.

K2 numbers will be assigned to all confirmed or validated planets where K2 data of that object appear in accepted, peer-reviewed journal papers. K2 numbers will also be assigned to previously known planets, but only after the K2 data have been published. All planets with assigned K2 numbers will be included in the Planetary Systems and Planetary Systems Composite Data tables at the NASA Exoplanet Archive.

See the K2 Confirmed Names interactive table for all confirmed planets that are assigned K2 numbers.

Following the Kepler prime mission convention, K2 candidates are identified by appending a two-digit identifier sequence number after the host star's EPIC identifier, separated by a period: e.g., EPIC 205071984.02 (K2-32 d). The sequence number for a K2 candidate within a system is designated by the discoverer; numbers should should be assigned in order of discovery and by order of period within a single discovery paper.

IMPORTANT: Check the K2 Planets and Candidates Table before assigning new candidate identifiers.

It is important to check any new K2 candidates that you identify against those that have already been identified and assigned identifiers in previous publications. You can do this by cross-checking against the Exoplanet Archive's K2 Planets and Candidates Table. Identifiers for different candidates orbiting a given host should be cross-matched using the candidate period. Note that, as for confirmed planets, once a candidate identifier has been assigned, it should not be re-used for a different candidate, even in the event the original candidate has been flagged as a false positive.

How to Request a K2 Number

To request K2 numbers for use in a published paper, please use the following procedure:

  1. Check the K2 Planets and Candidates table to see whether your targets have already been identified, and if so, which names or identifiers have been assigned. If you have also identified new, unconfirmed candidates, check those against the K2 Candidates table too.
  2. During preparation and submission of the paper, use an alternate name for each confirmed planet (e.g., EPIC number or K2-XX b).
  3. After the paper is accepted, but before the final page proofs are submitted, send an email to exonames (at) ipac (dot) caltech (dot) edu including:
    • A copy of the letter/notice of acceptance to a peer-reviewed journal
    • A copy of the accepted manuscript
    • A list of the objects which need K2 numbers, including their EPIC designations, and
    • The number of planets confirmed around each star.

    Letters for multiple planet systems will be assigned by increasing orbital period.

  4. K2 numbers will be assigned within two business days unless additional information is required.
  5. Once K2 numbers are received, replace the alternate (or placeholder) names with the new Kepler numbers as part of the final page-proof process.

Please note the editors of most major astronomical journals have approved this procedure. Newly assigned K2 numbers will be posted to the Exoplanet Archive once the paper is publicly available (at the journal, astro-ph, or other widely available site).

Last updated: 24 January 2022