The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution

Abstract

Since planet occurrence and primordial atmospheric retention probability increase with period, the occurrence-weighted median planets discovered by transit surveys may bear little resemblance to the low-occurrence, short-period planets sculpted by atmospheric escape ordinarily used to calibrate mass--radius relations and planet formation models. An occurrence-weighted mass--radius relation for the low-mass planets discovered so far by transit surveys orbiting solar-type stars requires both occurrence-weighted median Earth-mass and Neptune-mass planets to have a few percent of their masses in hydrogen/helium (H/He) atmospheres. Unlike the Earth that finished forming long after the protosolar nebula was dissipated, these occurrence-weighted median Earth-mass planets must have formed early in their systems' histories. The existence of significant H/He atmospheres around Earth-mass planets confirms an important prediction of the core-accretion model of planet formation. It also implies core masses $M_{\text{c}}$ in the range $2M_{\oplus }\lesssim M_{\text{c}}\lesssim 8M_{\oplus }$ that can retain their primordial atmospheres. If atmospheric escape is driven by photoevaporation due to extreme ultraviolet (EUV) flux, then our observation requires a reduction in the fraction of incident EUV flux converted into work usually assumed in photoevaporation models. If atmospheric escape is core driven, then the occurrence-weighted median Earth-mass planets must have large Bond albedos. In contrast to Uranus and Neptune that have at least 10% of their masses in H/He atmospheres, these occurrence-weighted median Neptune-mass planets are H/He poor. The implication is that they experienced collisions or formed in much shorter-lived and/or hotter parts of their parent protoplanetary disks than Uranus and Neptune's formation location in the protosolar nebula.

arXiv comment23 pages, 7 figures, and 1 table in aastex631 format; accepted for publication in ApJ

References in corpus (198)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• The SIMBAD astronomical database
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Disk Frequencies and Lifetimes in Young Clusters
• The VizieR database of Astronomical Catalogues
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• The false positive rate of Kepler and the occurrence of planets
• The NASA Exoplanet Archive: Data and Tools for Exoplanet Research
• Kepler planets: a tale of evaporation
• Architecture and Dynamics of Kepler's Candidate Multiple Transiting Planet Systems
• The evaporation valley in the Kepler planets
• Gaia Data Release 2: Photometric content and validation
• Gaia Data Release 2: using Gaia parallaxes
• Atmospheric Escape from Hot Jupiters
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• A Closely-Packed System of Low-Mass, Low-Density Planets Transiting Kepler-11
• The Occurrence Rate of Small Planets around Small Stars
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• Gaia Data Release 2: Catalogue validation
• Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius
• Growth Model Interpretation of Planet Size Distribution
• The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
• KEPLER's First Rocky Planet: Kepler-10b
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Core-powered mass loss and the radius distribution of small exoplanets
• Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets
• Towards a deterministic model of planetary formation. III. Mass distribution of short-period planets around stars of various masses
• Core-Accretion Model Predicts Few Jovian-Mass Planets Orbiting Red Dwarfs
• False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
• Planetary evaporation by UV & X-ray radiation: basic hydrodynamics
• Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog With Measured Completeness and Reliability Based on Data Release 25
• Timescale of Mass Accretion in Pre-Main-Sequence Stars
• How Thermal Evolution and Mass Loss Sculpt Populations of Super-Earths and Sub-Neptunes: Application to the Kepler-11 System and Beyond
• Gaia Data Release 1: Catalogue validation
• Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities
• Breaking the Chains: Hot Super-Earth systems from migration and disruption of compact resonant chains
• Detection of a NEPTUNE-mass planet in the ${\rho }^1$ Cancri system using the Hobby-Eberly Telescope
• Extracting Planet Mass and Eccentricity From TTV data
• Almost All of Kepler's Multiple Planet Candidates are Planets
• The Mass of KOI-94d and a Relation for Planet Radius, Mass, and Incident Flux
• Eccentricity from transit photometry: small planets in Kepler multi-planet systems have low eccentricities
• On the use of Gaia magnitudes and new tables of bolometric corrections
• Super-Earth Atmospheres: Self-Consistent Gas Accretion and Retention
• WASP-47: A Hot Jupiter System with Two Additional Planets Discovered by K2
• Probabilistic Mass-Radius Relationship for Sub-Neptune-Sized Planets
• Transit Timing Observations from Kepler: IV. Confirmation of 4 Multiple Planet Systems by Simple Physical Models
• Densities and Eccentricities of 139 Kepler Planets from Transit Time Variations
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• To Cool is to Accrete: Analytic Scalings for Nebular Accretion of Planetary Atmospheres
• Density and Eccentricity of Kepler Planets
• Atmospheres of low-mass planets: the "boil-off"
• The Nature of the Radius Valley: Hints from Formation and Evolution Models
• Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres
• Kepler Planet Masses and Eccentricities from TTV Analysis
• Alignment of the stellar spin with the orbits of a three-planet system
• The Exoplanet Census: A General Method, Applied to Kepler
• In-situ Accretion of Hydrogen-Rich Atmospheres on Short-Period Super-Earths: Implications for the Kepler-11 Planets
• An ancient extrasolar system with five sub-Earth-size planets
• 197 Candidates and 104 Validated Planets in K2's First Five Fields
• The Spitzer c2d Survey of Weak-line T Tauri Stars II: New Constraints on the Timescale for Planet Building
• Occurrence Rates of Planets orbiting FGK Stars: Combining Kepler DR25, Gaia DR2 and Bayesian Inference
• TESS Discovery of a Transiting Super-Earth in the $\pi$ Mensae System
• 3D maps of interstellar dust in the Local Arm: using $Gaia$, 2MASS and APOGEE-DR14
• Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry
• Very Low-Density Planets around Kepler-51 Revealed with Transit Timing Variations and an Anomaly Similar to a Planet-Planet Eclipse Event
• Kepler 18-b, c, and d: A System Of Three Planets Confirmed by Transit Timing Variations, Lightcurve Validation, Spitzer Photometry and Radial Velocity Measurements
• Transit Timing Observations from Kepler: VII. Confirmation of 27 planets in 13 multiplanet systems via Transit Timing Variations and orbital stability
• Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation
• Transit Timing Observations from Kepler: III. Confirmation of 4 Multiple Planet Systems by a Fourier-Domain Study of Anti-correlated Transit Timing Variations
• Asteroseismic determination of obliquities of the exoplanet systems Kepler-50 and Kepler-65
• The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars
• 275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0-10
• The Detection and Characterization of a Nontransiting Planet by Transit Timing Variations
• Transits and Occultations of an Earth-Sized Planet in an 8.5-Hour Orbit
• Gaia Data Release 2: processing of the photometric data
• Influence of Stellar Multiplicity On Planet Formation. I. Evidence of Suppressed Planet Formation Due to Stellar Companions Within 20 AU and Validation of Four Planets From the Kepler Multiple Planet Candidates
• The HARPS-N Rocky Planet Search I. HD219134b: A transiting rocky planet in a multi-planet system at 6.5 pc from the Sun
• The Kepler-19 System: A Transiting 2.2 R_Earth Planet and a Second Planet Detected via Transit Timing Variations
• Gaia Data Release 2. Cross-match with external catalogues - Algorithms and results
• HAT-P-26b: A Low-Density Neptune-Mass Planet Transiting a K Star
• An ultra-short period rocky super-Earth with a secondary eclipse and a Neptune-like companion around K2-141
• Kepler-21b: A 1.6REarth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070
• TESS's first planet: a super-Earth transiting the naked-eye star $\pi$ Mensae
• A giant impact as the likely origin of different twins in the Kepler-107 exoplanet system
• Kepler-20: A Sun-like Star with Three Sub-Neptune Exoplanets and Two Earth-size Candidates
• Eleven Multi-planet Systems from K2 Campaigns 1 & 2 and the Masses of Two Hot Super-Earths
• Kepler-4b: Hot Neptune-Like Planet of a G0 Star Near Main-Sequence Turnoff
• Transit Timing Variation of Near-Resonance Planetary Pairs. II. Confirmation of 30 planets in 15 Multiple Planet Systems
• Kepler-21b: A rocky planet around a V = 8.25 magnitude star
• Occurrence Rates of Planets Orbiting M Stars: Applying ABC to Kepler DR25, Gaia DR2, and 2MASS Data
• Kepler-10c, a 2.2-Earth radius transiting planet in a multiple system
• Kepler-68: Three Planets, One With a Density Between That of Earth and Ice Giants
• The NASA-UC Eta-Earth Program: III. A Super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785
• Characterizing K2 Planet Discoveries: A super-Earth transiting the bright K-dwarf HIP 116454
• Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions
• Three's Company: An additional non-transiting super-Earth in the bright HD 3167 system, and masses for all three planets
• A 1.9 Earth radius rocky planet and the discovery of a non-transiting planet in the Kepler-20 system
• Four Sub-Saturns with Dissimilar Densities: Windows into Planetary Cores and Envelopes
• Two massive rocky planets transiting a K-dwarf 6.5 parsecs away
• Transit Timing Variation of Near-Resonance Planetary Pairs: Confirmation of Twelve Multiple Planet Systems
• Primordial Radius Gap and Potentially Broad Core Mass Distributions of Super-Earths and Sub-Neptunes
• Planet Hunters VII. Discovery of a New Low-Mass, Low-Density Planet (PH3 c) Orbiting Kepler-289 with Mass Measurements of Two Additional Planets (PH3 b and d)
• NGTS-4b: A sub-Neptune Transiting in the Desert
• The Planetary Mass-Radius Relation and its Dependence on Orbital Period as Measured by Transit Timing Variations and Radial Velocities
• TESS delivers its first Earth-sized planet and a warm sub-Neptune
• EUV irradiation of exoplanet atmospheres occurs on Gyr timescales
• The K2-138 System: A Near-Resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists
• Diffuser-Assisted Infrared Transit Photometry for Four Dynamically Interacting \textit{Kepler} Systems
• The HARPS search for southern extra-solar planets. XXXVI. Eight HARPS multi-planet systems hosting 20 super-Earth and Neptune-mass companions
• How planets grow by pebble accretion. III. Emergence of an interior composition gradient
• An Independent Planet Search In The Kepler Dataset. II. An extremely low-density super-Earth mass planet around Kepler-87
• Transit confirmation and improved stellar and planet parameters for the super-Earth HD 97658 b and its host star
• Spectral Properties of Cool Stars: Extended Abundance Analysis of Kepler Objects of Interest
• Two Small Planets Transiting HD 3167
• Kepler-411: a four-planet system with an active host star
• HD 213885b: A transiting 1-day-period super-Earth with an Earth-like composition around a bright ($V=7.9$) star unveiled by TESS
• The discovery and mass measurement of a new ultra-short-period planet: EPIC~228732031b
• Precise Masses in the WASP-47 System
• Predicting Exoplanets Mass and Radius: A Nonparametric Approach
• Effect of Non-Adiabatic Thermal Profiles on the Inferred Compositions of Uranus and Neptune
• K2-106, a system containing a metal-rich planet and a planet of lower density
• Mass-Radius relationship for M dwarf exoplanets: Comparing nonparametric and parametric methods
• An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561
• Sensitivity bias in the mass-radius distribution from Transit Timing Variations and Radial Velocity measurements
• The Kepler-19 system: a thick-envelope super-Earth with two Neptune-mass companions characterized using Radial Velocities and Transit Timing Variations
• Evolution of the Exoplanet Size Distribution: Forming Large Super-Earths Over Billions of Years
• A Joint Mass-Radius-Period Distribution of Exoplanets
• Super-Earth of 8 Mearth in a 2.2-day orbit around the K5V star K2-216
• Most super-Earths formed by dry pebble accretion are less massive than 5 Earth masses
• Doppler Monitoring of five K2 Transiting Planetary Systems
• The SOPHIE search for northern extrasolar planets. XVI. HD 158259: A compact planetary system in a near-3:2 mean motion resonance chain
• The TESS-Keck Survey II: An Ultra-Short Period Rocky Planet and its Siblings Transiting the Galactic Thick-Disk Star TOI-561
• The Transiting Multi-planet System HD15337: Two Nearly Equal-mass Planets Straddling the Radius Gap
• Exoplanet characterisation in the longest known resonant chain: the K2-138 system seen by HARPS
• EPIC 210894022b - A short period super-Earth transiting a metal poor, evolved old star
• K2-111: an old system with two planets in near-resonance
• Long-Period Giant Companions to Three Compact, Multiplanet Systems
• Pinning down the mass of Kepler-10c: the importance of sampling and model comparison
• Dynamics and Formation of the Near-Resonant K2-24 System: Insights from Transit-Timing Variations and Radial Velocities
• Two Small Transiting Planets and a Possible Third Body Orbiting HD 106315
• Mass determinations of the three mini-Neptunes transiting TOI-125
• HD219666b: A hot-Neptune from TESS Sector 1
• K2-66b and K2-106b: Two extremely hot sub-Neptune-size planets with high densities
• Two Transiting Low Density Sub-Saturns from K2
• TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes
• Near-resonance in a system of sub-Neptunes from TESS
• The Kepler-454 System: A Small, Not-rocky Inner Planet, a Jovian World, and a Distant Companion
• TESS exoplanet candidates validated with HARPS archival data. A massive Neptune around GJ143 and two Neptunes around HD23472
• The Magellan-TESS Survey I: Survey Description and Mid-Survey Results
• Formation of Venus, Earth and Mars: Constrained by isotopes
• HD 89345: a bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2
• A resonant pair of warm giant planets revealed by TESS
• Gaia Data Release 2. Calibration and mitigation of electronic offset effects in the data
• A sub-Neptune and a non-transiting Neptune-mass companion unveiled by ESPRESSO around the bright late-F dwarf HD 5278 (TOI-130)
• Precise masses for the transiting planetary system HD 106315 with HARPS
• TESS Reveals a Short-period Sub-Neptune Sibling (HD 86226c) to a Known Long-period Giant Planet
• Discovery and Validation of a High-Density sub-Neptune from the K2 Mission
• Transits of Known Planets Orbiting a Naked-Eye Star
• SOPHIE velocimetry of Kepler transit candidates XIV. A joint photometric, spectroscopic, and dynamical analysis of the Kepler-117 system
• K2-98 b: A 32-M${}_{\oplus }$ Neptune-sized planet in a 10-day orbit transiting an F8 star
• TOI-132 b: A short-period planet in the Neptune desert transiting a $V=11.3$ G-type star
• An ultra-short period rocky super-Earth orbiting the G2-star HD 80653
• Beyond the exoplanet mass-radius relation
• Detection and Doppler monitoring of EPIC 246471491, a system of four transiting planets smaller than Neptune
• Ultra Short Period Planets in K2 with companions: a double transiting system for EPIC 220674823
• K2-110 b - a massive mini-Neptune exoplanet
• Transiting exoplanets from the CoRoT space mission: XXVI. CoRoT-24: A transiting multi-planet system
• An accurate mass determination for Kepler-1655b, a moderately-irradiated world with a significant volatile envelope
• K2-265 b: A Transiting Rocky Super-Earth
• Evidence of a Sub-Saturn around EPIC~211945201
• The TOI-763 system: sub-Neptunes orbiting a Sun-like star
• Detection and characterization of an ultra-dense sub-Neptune planet orbiting the Sun-like star HD 119130
• The K2-ESPRINT Project II: Spectroscopic follow-up of three exoplanet systems from Campaign 1 of K2
• Three planets transiting the evolved star EPIC 249893012: a hot 8.8-M${}_{\oplus }$ super-Earth and two warm 14.7 and 10.2-M${}_{\oplus }$ sub-Neptunes
• HATS-43b, HATS-44b, HATS-45b, and HATS-46b: Four Short Period Transiting Giant Planets in the Neptune-Jupiter Mass Range
• Unified simulations of planetary formation and atmospheric evolution II: Rapid disk clearing by photoevaporation yields low-mass super-Earth atmospheres
• Two warm, low-density sub-Jovian planets orbiting bright stars in K2 campaigns 13 and 14
• A Simplified Photodynamical Model for Planetary Mass Determination in Low-Eccentricity Multi-Transiting Systems
• Two Super-Earths in the 3:2 MMR around KOI-1599
• NGTS-14Ab: a Neptune-sized transiting planet in the desert
• K2-291 b: A rocky super-Earth in a 2.2 day orbit
• Masses of Kepler-46b, c from Transit Timing Variations
• CoRoT-22 b: a validated 4.9 RE exoplanet in 10-day orbit
• A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113
• An 11 Earth-Mass, Long-Period Sub-Neptune Orbiting a Sun-like Star
• So close, so different: characterization of the K2-36 planetary system with HARPS-N
• TOI-220 $b$: a warm sub-Neptune discovered by TESS
• K2-263b: A 50-day period sub-Neptune with a mass measurement using HARPS-N
• HATS-37Ab and HATS-38b: Two Transiting Hot Neptunes in the Desert
• The K2-ESPRINT Project VI: K2-105 b, a Hot-Neptune around a Metal-rich G-dwarf
• A modified CoRoT detrend algorithm and the discovery of a new planetary companion
• Formation of Planetary Populations III: Core Composition & Atmospheric Evaporation
• Validation of HD 183579b using archival radial velocities: a warm-neptune orbiting a bright solar analog
• The multi-planet system TOI-421 -- A warm Neptune and a super puffy mini-Neptune transiting a G9 V star in a visual binary
• Kepler Object of Interest Network III. Kepler-82f: A new non-transiting $21 M_\bigoplus$ planet from photodynamical modelling