Exoplanets & Exomoons

The Demographics of Exoplanets

By Keith Cowing
November 11, 2020
Filed under
The Demographics of Exoplanets
The distributions of the ∼4300 confirmed low mass companions to stars as a function of their mass and period (left) and radius and period (right) where the conversion to semi-major access is derived using Kepler’s third law. The color coding denotes the method by which planets were detected. Some of the features in these diagrams are real, however many are due to the selection effects. For example, the large population of 1–4 R⊕ planets in the right panel is largely missing in the left panel due to the fact that these planets were primarily detected by Kepler, and thus typically have host stars that are too faint to enable a measurement of their mass via radial velocity. Similarly, the fact that there are nearly equal numbers of Hot Jupiters as cold Jupiters in the left panel is due to the fact that ground-based transit surveys, which have larger sample sizes than radial velocity surveys, are primarily sensitive to Hot Jupiters. Thus Hot Jupiters are over-represented in the figures. Finally, the paucity of planets in the lower-right corner of each plot is purely a selection effect due to the fact that the radial velocity, transit, and direct imaging methods are not currently sensitive to planets in this region of parameter space. Based on data from the NASA Exoplanet Archive: <a href="https://exoplanetarchive.ipac.caltech.edu/">https://exoplanetarchive.ipac.caltech.edu/</a>.

In the broadest sense, the primary goal of exoplanet demographic surveys is to determine the frequency and distribution of planets as a function of as many of the physical parameters that may influence planet formation and evolution as possible, over as broad of a range of these parameters as possible.

Empirically-determined exoplanet demographics provide the ground truth that all planet formation and evolution theories must reproduce. By comparing these planet distributions to the predictions of planet formation theories, we can begin to both test and refine these theories.

In this chapter, we review the major results on exoplanet demographics to date. In this context, we identify a set of important open questions that remain to be answered. We outline the challenges of measuring the demographics of exoplanets using the variety of detection methods at our disposal. Finally, we summarize some of the future opportunities for refining and expanding our understanding of exoplanet demographics.

B. Scott Gaudi, Jessie L. Christiansen, Michael R. Meyer Comments: 25 pages, 3 figures. To appear as a book chapter in “ExoFrontiers: Big questions in exoplanetary science”, Ed. N Madhusudhan (Bristol: IOP Publishing Ltd) AAS-IOP ebooks, this https URL Subjects:

Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar
Astrophysics (astro-ph.SR) Cite as: arXiv:2011.04703 [astro-ph.EP] (or arXiv:2011.04703v1 [astro-ph.EP] for this version) Submission history From: B. Scott Gaudi
[v1] Mon, 9 Nov 2020 19:29:30 UTC (6,018 KB)

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