A REVISED ESTIMATE OF THE OCCURRENCE RATE OF TERRESTRIAL PLANETS IN THE HABITABLE ZONES AROUND KEPLER M-DWARFS

By R. Kopparapu. 2013

198 citations recorded by the source corpus.

Because of their large numbers, low-mass stars may be the most abundant planet hosts in our Galaxy. Furthermore, terrestrial planets in the habitable zones (HZs) around M-dwarfs can potentially be characterized in the near future and hence may be the first such planets to be studied. Recently, Dressing & Charbonneau used Kepler data and calculated the frequency of terrestrial planets in the HZ of cool stars to be per star for Earth-size planets (0.5–1.4 R⊕). However, this estimate was derived using the Kasting et al. HZ limits, which were not valid for stars with effective temperatures lower than 3700 K. Here we update their result using new HZ limits from Kopparapu et al. for stars with effective temperatures between 2600 K and 7200 K, which includes the cool M stars in the Kepler target list. The new HZ boundaries increase the number of planet candidates in the HZ. Assuming Earth-size planets as 0.5–1.4 R⊕, when we reanalyze their results, we obtain a terrestrial planet frequency of and planets per M-dwarf star for conservative and optimistic limits of the HZ boundaries, respectively. Assuming Earth-size planets as 0.5–2 R⊕, the frequency increases to per star for the conservative estimate and to per star for the optimistic estimate. Within uncertainties, our optimistic estimates are in agreement with a similar optimistic estimate from the radial velocity survey of M-dwarfs (). So, the potential for finding Earth-like planets around M stars may be higher than previously reported.

Subfields: Astronomy and Astrophysics

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In Astronomy and Astrophysics

1. D. Charbonneau
2. A. Mann
3. E. Gaidos
4. C. Dressing
5. Timothy Morton
6. J. Johnson
7. J. Winn
8. L. Kaltenegger

Citations in the corpus

• Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life (2014, background): “Some Keplerdetected planets orbiting very cool (late K- and M-type) dwarfs are near or inside the theoretical “habitable zones” of these stars where an Earth-like planet could have liquid water on its surface (Dressing & Charbonneau 2013; Kopparapu 2013; Gaidos 2013; Quintana et al. 2014).”
• STRONG DEPENDENCE OF THE INNER EDGE OF THE HABITABLE ZONE ON PLANETARY ROTATION RATE (2014, background): “Accurate estimates of the stellar flux boundaries of the habitable zone are critical for estimating parameters of astrophysical interest such as the frequency of Earth-like planets (e.g., Kopparapu 2013).”
• HABITABLE ZONES AROUND MAIN-SEQUENCE STARS: DEPENDENCE ON PLANETARY MASS (2014, background): “; Anglada-Escude et al. 2013), and it is expected that this number will greatly increase as time passes (Dressing & Charbonneau 2013; Kopparapu 2013; Gaidos 2013).”
• MAXIMIZING THE ExoEarth CANDIDATE YIELD FROM A FUTURE DIRECT IMAGING MISSION (2014, background): “This does not incoporate the fact that exoEarth candidates may be more common around M stars, with estimates converging on η⊕ ≈ 0.4 for M stars (Bonfils et al. 2013; Kopparapu 2013).”
• THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW (2016, unknown): “The importance of M dwarf exoplanetary systems is underscored by recent Kepler results and radial velocity measurements showing that between ∼ 10 – 50% of M dwarfs host Earth-size planets (0.5 – 1.4 R⊕) in their HZs (Dressing & Charbonneau 2015; Kopparapu 2013; Bonfils et al. 2013).”
• THE RADIUS DISTRIBUTION OF PLANETS AROUND COOL STARS (2013, methodology): “And if this same correction is made to the calculations of Kopparapu (2013), which use updated HZ calculations but the same occurrence formalism as Dressing & Charbonneau (2013), than this number would become closer to ∼0.8 planet per star.”
• The Occurrence and Architecture of Exoplanetary Systems (2014, background): “Likewise, Dressing & Charbonneau (2013) and Kopparapu (2013) used the same probability density to derive occurrence rates differing by a factor of three.”
• The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “…that the best place to look for habitable planets may be around M-dwarf stars (Joshi et al., 1997; Joshi, 2003; Selsis et al., 2007; Wordsworth et al., 2010; Joshi & Haberle, 2012; Shields et al., 2013; Kopparapu, 2013; Shields et al., 2014; Dressing & Charbonneau, 2015; Gale & Wandel, 2015).”
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, background): “The observations of the Proxima system (Anglada-Escudé et al. 2016) show that Proxima b is located in the classical insolation HZ (as defined in Kasting et al. 1993; Selsis et al. 2007b; Kopparapu 2013; Kopparapu et al. 2014).”
• HAZMAT. I. THE EVOLUTION OF FAR-UV AND NEAR-UV EMISSION FROM EARLY M STARS (2014, background): “…of M dwarfs provide a favorable environment for the formation of low-mass planets close to the star (Wu & Lithwick 2013), as indicated by the ∼50% small planet occurrence rate around M dwarfs in the habitable zone (HZ; ≈0.1–0.4 AU; Bonfils et al. 2013; Kopparapu 2013; Dressing & Charbonneau 2014).”
• SPECTRO-THERMOMETRY OF M DWARFS AND THEIR CANDIDATE PLANETS: TOO HOT, TOO COOL, OR JUST RIGHT? (2013, background): “A third planet, KOI 2418.01, is significantly (2.7σ) outside the CO2 condensation definition of the limit of the HZ, but falls within the ‘maximum CO2 greenhouse definition of the outer limit used by Kopparapu (2013).”
• 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): “Kopparapu (2013) then revised this estimate to 0.48+0.12 −0.24 planets per star using the broader updated habitable zone boundaries from Kopparapu et al. (2013b).”