Exoplanets & Exomoons

Planet Occurrence From Doppler And Transit Surveys

By Keith Cowing
Status Report
February 1, 2024
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Planet Occurrence From Doppler And Transit Surveys
Idealized Doppler and transit surveys. The top panel shows the results of a Doppler survey in which 100 Sun-like stars are each observed 50 times over one year with 1 m s−1 precision. The bottom panel shows the results of a transit survey in which 104 stars are observed continuously for a year with a photometric precision corresponding to 3×10−5 per 6 hours of data. Each star is assumed to have one planet on a randomly-oriented circular orbit, with random properties drawn from log-uniform distributions between the plotted limits. Colored points are planets detected with a signal-to-noise ratio (SNR) exceeding 10. Gray points are undetected planets. In the Doppler survey, the threshold mass scales as P 1/3 for periods shorter than the survey duration. For longer periods, the threshold mass increases more rapidly, with an exponent depending on the desired false-alarm probability (Cumming 2004). The transit survey includes more stars, because they can be monitored simultaneously, but detects a smaller fraction of the planets and is more strongly biased toward short periods. For periods shorter than survey duration, the threshold radius varies as P 1/6 (Pepper et al. 2003). For longer periods it is impossible to observe more than one transit, making any detections more ambiguous. — astro-ph.EP

Prior to the 1990s, speculations about the occurrence of planets around other stars were based only on planet formation theory, observations of circumstellar disks, and the knowledge that at least one seemingly ordinary star is the host of four terrestrial planets, two gas giants, and two ice giants.

Since then, Doppler and transit surveys have been exploring the population of planets around other Sun-like stars, especially those with orbital periods shorter than a few years. Over the last decade, these surveys have risen to new heights with Doppler spectrographs with a precision better than 1 m/s precision, and space telescopes capable of detecting the transits of Earth-sized planets.

This article is a brief introductory review of the knowledge of planet occurrence that has been gained from these surveys.

Joshua N. Winn, Erik Petigura

Comments: To be published in: Handbook of Exoplanets, 2nd Edition, Hans Deeg and Juan Antonio Belmonte (Eds. in Chief), Springer International Publishing AG, part of Springer Nature. arXiv admin note: text overlap with arXiv:1801.08543
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2401.16451 [astro-ph.EP] (or arXiv:2401.16451v1 [astro-ph.EP] for this version)
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Submission history
From: Josh Winn
[v1] Mon, 29 Jan 2024 03:14:56 UTC (558 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻