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Exoplanets Period Distribution

Histogram of the exoplanets period distribution

A histogram showing the distribution of the orbital periods of the confirmed exoplanets in a subset of the sample that have measured orbital periods (subsample from a snapshot on 5 August, 2012). Plotted is the percentage of the subsample of exoplanets in each period interval. The exoplanet periods are shown in units of Earth days. Data are from the Extrasolar Planets Encyclopedia. For comparison, the periods of objects in our solar system are marked as Me, V, E, Ma, J, S, U, N, P corresponding to Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto respectively (numerical values are from

It can be seen that the orbital period distribution is conspicuously bimodel, wih a broad peak between about 100 to 10000 Earth years, and a narrower peak between about 2 and 6 Earth days. The latter peak corresponds to the numerous hot Jupiters and other close-in planets that have been a hallmark of exoplanet discoveries. Since the star-planet distance is related to the orbital period by Kepler's laws, the distribution of the semimajor axis of exoplanet orbits also shows a marked bimodel characteristic. The origin of the form of the distributions is puzzling, and there is as yet no concensus on the physics driving the distributions. There are possible selection effects that need to be considered for interpretation of the data. A more detailed discussion can be found in the book Exoplanets and Alien Solar Systems, which includes comprehensive references to the scientific literature.

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Note: There are 751 exoplanets that contribute to the orbital period histogram, taken from a snapshot (on 5 August, 2012) when there were 777 confirmed exoplanets in total (residing in 623 alien solar systems, 105 of which harbored more than one exoplanet).
File under: Distribution of orbital periods of exoplanets. What is the range in orbital periods of exoplanets? What orbital periods do exoplanets have? What is the fastest and longest time in which an exoplanet has been observed to complete an orbit around its star?

© Tahir Yaqoob 2011-2012.