A PLATEAU IN THE PLANET POPULATION BELOW TWICE THE SIZE OF EARTH

By E. Petigura, G. Marcy, Andrew W. Howard. 2013

227 citations recorded by the source corpus.

We carry out an independent search of Kepler photometry for small transiting planets with sizes 0.5–8.0 times that of Earth and orbital periods between 5 and 50 days, with the goal of measuring the fraction of stars harboring such planets. We use a new transit search algorithm, TERRA, optimized to detect small planets around photometrically quiet stars. We restrict our stellar sample to include the 12,000 stars having the lowest photometric noise in the Kepler survey, thereby maximizing the detectability of Earth-size planets. We report 129 planet candidates having radii less than 6 RE found in three years of Kepler photometry (quarters 1–12). Forty-seven of these candidates are not in Batalha et al., which only analyzed photometry from quarters 1–6. We gather Keck HIRES spectra for the majority of these targets leading to precise stellar radii and hence precise planet radii. We make a detailed measurement of the completeness of our planet search. We inject synthetic dimmings from mock transiting planets into the actual Kepler photometry. We then analyze that injected photometry with our TERRA pipeline to assess our detection completeness for planets of different sizes and orbital periods. We compute the occurrence of planets as a function of planet radius and period, correcting for the detection completeness as well as the geometric probability of transit, R⋆/a. The resulting distribution of planet sizes exhibits a power law rise in occurrence from 5.7 RE down to 2 RE, as found in Howard et al. That rise clearly ends at 2 RE. The occurrence of planets is consistent with constant from 2 RE toward 1 RE. This unexpected plateau in planet occurrence at 2 RE suggests distinct planet formation processes for planets above and below 2 RE. We find that % of solar type stars—roughly one in six—has a 1–2 RE planet with P = 5–50 days.

Subfields: Astronomy and Astrophysics, Instrumentation

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In Astronomy and Astrophysics

1. D. Charbonneau
2. Jon Fortney
3. Timothy Morton
4. J. Johnson
5. J. Winn
6. Andrew W. Howard
7. G. Marcy
8. J. Owen

In Instrumentation

1. D. Charbonneau
2. Jon Fortney
3. Timothy Morton
4. J. Johnson
5. J. Winn
6. E. Gaidos
7. J. Owen
8. G. Marcy

Citations in the corpus

• A SYSTEMATIC SEARCH FOR TRANSITING PLANETS IN THE K2 DATA (2015, methodology): “This project follows in the tradition of independently implemented transit search algo- rithms applied to publicly available datasets (such as Petigura et al. 2013b,a; Sanchis-Ojeda et al. 2014; Dressing & Charbonneau 2015).”
• THE OCCURRENCE OF POTENTIALLY HABITABLE PLANETS ORBITING M DWARFS ESTIMATED FROM THE FULL KEPLER DATASET AND AN EMPIRICAL MEASUREMENT OF THE DETECTION SENSITIVITY (2015, methodology): “After searching for planets around 42,557 relatively quiet GK stars, Petigura et al. (2013a) found that 7.7 ± 1.3% of GK stars host small planets (1 − 2R⊕) in periods between 25 and 50 days.”
• An ALMA Survey of Protoplanetary Disks in the σ Orionis Cluster (2017, background): “…with masses between that of Earth and Neptune) appear to be an order of magnitude more abundant than gas giants (i.e., planets with masses several times that of Jupiter), at least for short orbital periods (Howard et al. 2012; Fressin et al. 2013; Petigura et al. 2013; Gaidos et al. 2016).”
• KEPLER PLANETS: A TALE OF EVAPORATION (2013, background): “Although most careful studies to date have yet to have sufficient radius resolution to confirm this feature (Howard et al. 2012; Petigura et al. 2013; Fressin et al. 2013), it is hinted at by Morton & Swift (2013) who construct a probability distribution function rather than using histograms with…”
• Identifying Exoplanets with Deep Learning: A Five-planet Resonant Chain around Kepler-80 and an Eighth Planet around Kepler-90 (2017, background): “As the Kepler mission matured and the list of planet candidates grew, the focus of the community shifted towards population-level studies (Fressin et al. 2013; Petigura et al. 2013a,b; Foreman-Mackey et al. 2014; Dressing & Charbonneau 2013, 2015; Burke et al. 2015; Mulders et al. 2015a,b).”
• Optimized transit detection algorithm to search for periodic transits of small planets (2019, methodology): “Transit searches using the BLS algorithm usually operate with trial transit durations3 T14 that span 0.00125 – 0.07 (Petigura et al. 2013), 0.01 – 0.1 (Giacobbe et al. 2012), or 0.001 – 0.2 (Sanchis-Ojeda et al. 2014; Aigrain et al. 2016) times the orbital period.”
• Photoevaporation and high-eccentricity migration created the sub-Jovian desert (2018, background): “Lower mass and smaller planets (Rp ∼ 1− 4 R⊕) have now been found in abundance at short periods as well (e.g. Borucki et al. 2011; Fressin et al. 2013; Petigura et al. 2013; Silburt et al. 2015; Mulders et al. 2016).”
• The Exoplanet Population Observation Simulator. I. The Inner Edges of Planetary Systems (2018, background): “The planet radius distribution function is similarly described by a broken power law = <⎧⎨⎩( ) ( ) ( ) ( )f R R R R R R R , if , otherwise 4R a b break break break R R reflecting the observed increase of small planets with decreasing radius (bR=−4), and the “plateau” (aR=0) of constant occurrence ra”
• EXOPLANET POPULATION INFERENCE AND THE ABUNDANCE OF EARTH ANALOGS FROM NOISY, INCOMPLETE CATALOGS (2014, methodology): “Instead of choosing a functional form for the detection efficiency of the pipeline as a function of the parameters of interest, Petigura et al. (2013a) injected synthetic signals of known period and radius into the raw aperture photometry and determined the empirical recovery after the full…”
• The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets (2017, background): “Further work showed that Earth-size planets are common in and near the habitable zone (Petigura et al. 2013a; Dressing & Charbonneau 2015; Burke et al. 2015).”
• UNDERSTANDING THE MASS–RADIUS RELATION FOR SUB-NEPTUNES: RADIUS AS A PROXY FOR COMPOSITION (2013, background): “In particular, Fressin et al. (2013) and Petigura et al. (2013) found that there is a sharp, roughly power-law like drop off in the frequency of planet occurrence above∼3 R⊕, while below this there a plateau in the plant occurrence rate down to at least 1 R⊕.”
• REVISED STELLAR PROPERTIES OF KEPLER TARGETS FOR THE QUARTER 1–16 TRANSIT DETECTION RUN (2013, methodology): “…planet-occurrence rates using the Kepler sample (e.g., Catanzarite & Shao 2011; Howard et al. 2012; Traub 2012; Dong & Zhu 2013; Fressin et al. 2013; Petigura et al. 2013a,b), have mostly relied on stellar properties based on the Kepler Input Catalog (KIC, Brown et al. 2011, hereafter B11).”
• SPITZER OBSERVATIONS CONFIRM AND RESCUE THE HABITABLE-ZONE SUPER-EARTH K2-18b FOR FUTURE CHARACTERIZATION (2016, background): “…first telescope with the sensitivity to detect small planets in the habitable zones of sun-like stars, indicate that the occurrence rate for habitable Earths (“η⊕”) may be as high as 5-20% (Petigura et al. 2013; Foreman-Mackey et al. 2014; Silburt et al. 2015; Farr et al. 2015; Burke et al. 2015).”
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets (2017, background): “Following the definitions in Petigura et al. (2013a), the average planet occurrence rate (number of planets per star) for any discrete bin in planet radius or orbital period is the sum of these weights divided by the total number of stars in the sample (N?)”
• ALMA SURVEY OF LUPUS PROTOPLANETARY DISKS. I. DUST AND GAS MASSES (2016, background): “If gas depletion is common in disks, this may help explain the unexpected prevalence of super-Earths and scarcity of gas giants seen in the exoplanet population (Howard et al. 2012; Petigura et al. 2013; Marcy et al. 2014).”
• TERRESTRIAL PLANET OCCURRENCE RATES FOR THE KEPLER GK DWARF SAMPLE (2015, methodology): “Our β = −0.68 is ∼2-σ (statistical uncertainty alone) shallower than the βp = −1 dependence qualitatively stated in Petigura et al. (2013b).”
• VALIDATION OF KEPLER'S MULTIPLE PLANET CANDIDATES. III. LIGHT CURVE ANALYSIS AND ANNOUNCEMENT OF HUNDREDS OF NEW MULTI-PLANET SYSTEMS (2014, methodology): “SpecMatch fitting (see below and Petigura et al. 2013) using spectra taken at the Keck I telescope.”
• The Gaia–Kepler Stellar Properties Catalog. I. Homogeneous Fundamental Properties for 186,301 Kepler Stars (2020, background): “…Fellow The first Kepler Stellar Properties Catalog (KSPC, Huber et al. 2014) was published to consolidate all of the follow-up work done for Kepler stars and improve the estimated planetary occurrence rates (e.g., Howard et al. 2012; Petigura et al. 2013; Burke et al. 2015; Fulton et al. 2017).”