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Occurrence of Earth-like planets around GKM Stars

posted Nov 5, 2013, 8:12 AM by Abel Mendez   [ updated Nov 5, 2013, 8:47 AM ]
Here we combine and interpret results from Kopparapu (2013) and Petigura et al. (2013) on the occurrence of Earth-like planets around red-dwarf (type M) and Sun-like (type G and K) stars, respectively. Both studies used NASA Kepler results. Based on their occurrence estimates we calculated the mean separation and 95% confidence distance for the solar neighborhood (<10pc). These numbers suggest that there is over a 95% probability of finding an Earth-like planet around a Sun-like star in the solar neighborhood. The probability is higher for those around M-dwarf stars.

Table 1. Occurrence (ηE), separation (δ), and 95% confidence distance (d95%) of Earth-like planets (0.5 — 2.0 RE in the HZ) around M-dwarfs and GK stars. The study of Petigura et al. (2013) only considered 1.0 — 2.0 RE planets. Calculations assume that there are 198 stellar systems with M-dwarf stars and 50 with GK-stars in the solar neighborhood (<10pc).

 

 

M-dwarfs (Kopparapu, 2013)

GK stars (Petigura et al., 2013)

Habitable Zone Definition

a (AU)*

ηE

δ(ly)

dE 95% (ly)

ηE

δ(ly)

dE 95% (ly)

Conservative (1)

0.99 — 1.69

0.51 +0.10/-0.20

6.25

10.1

0.086 ± 0.03

17.9

28.9

Empirical (1)

0.75 — 1.84

0.61 +0.07/-0.15

5.89

9.51

0.14 ± 0.05

15.2

24.6

Simple Flux (2)

0.5 — 2

0.22 ± 0.08

13.1

21.1

Desert-H2 Planets (3)

0.38 — 10

0.52 ± 0.19

9.8

15.9

HZ References: (1) Kopparapu et al., 2013; (2) Petigura et al., 2013; (3) Zsom et al., 2013; Pierrehumbert and Gaidos, 2011

Table Notes:
a = semi-major axis (values shown for G stars, check here for other types of stars).
ηE (eta Earth) = fraction of Earth-like planets per star.
δ(delta Earth) = mean distance between stellar systems with Earth-like planets.
d95% = 95% confidence distance for an Earth-like planet.