a Lack of Short-Period Multiplanet Systems With Close-Proximity Pairs and the Curious Case of Kepler-42

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Colleges, School and Institutes


Many Kepler multiplanet systems have planet pairs near low-order, mean-motion resonances. In addition, many Kepler multiplanet systems have planets with orbital periods less than a few days. With the exception of Kepler-42, however, there are no examples of systems with both short orbital periods and nearby companion planets while our statistical analysis predicts ~17 such pairs. For orbital periods of the inner planet that are less than three days, the minimum period ratio of adjacent planet pairs follows the rough constraint . This absence is not due to a lack of planets with short orbital periods. We also show a statistically significant excess of small, single-candidate systems with orbital periods below three days over the number of multiple candidate systems with similar periods—perhaps a small-planet counterpart to the hot Jupiters.


Original languageEnglish
Pages (from-to)L12
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 2013


  • celestial mechanics, methods: data analysis, methods: statistical, planets and satellites: formation