Habitable Zones Around Nearby Stars

The Solar Neighborhood XXIX: The Habitable Real Estate of our Nearest Stellar Neighbors

Justin R. Cantrell, Todd J. Henry, Russel J. White Georgia State University, Atlanta, GA 30302-4106 cantrell@chara.gsu.edu, thenry@chara.gsu.edu, white@chara.gsu.edu
Abstract

We use the sample of known stars and brown dwarfs within 5 pc of the Sun, supplemented with AFGK stars within 10 pc, to determine which stellar spectral types provide the most habitable real estate — defined to be locations where liquid water could be present on Earth-like planets. Stellar temperatures and radii are determined by fitting model spectra to spatially resolved broad-band photometric energy distributions for stars in the sample. Using these values, the locations of the habitable zones are calculated using an empirical formula for planetary surface temperature and assuming the condition of liquid water, called here the empirical habitable zone, or EHZ. Systems that have dynamically disruptive companions, assuming a 5:1 separation ratios for primary/secondary pairs and either object and a planet, are considered not habitable. We use the results of these calculations to derive a simple formula to predict the location of the EHZ for main sequence stars based on color. We consider EHZ widths as more useful measures of the habitable real estate around stars than areas because multiple planets are not expected to orbit stars at identical stellar distances. This EHZ provides a qualitative guide on where to expect the largest population of planets in the habitable zone of main sequence stars. Because of their large numbers and lower frequency of short-period companions, M stars provide more EHZ real estate than other spectral types, possessing 36.5% of the habitable real estate en masse. K stars are second with 21.5%, while A, F, and G stars offer 18.5%, 6.9% and 16.6%, respectively. Our calculations show that three M dwarfs within 10 pc harbor planets in their EHZs — GJ 581 may have two planets (d with sin = 6.1 ; g with sin = 3.1 ), GJ 667 C has one (c with sin = 4.5 ), and GJ 876 has two (b with sin = 1.89 and c with sin = 0.56 ). If Earth-like planets are as common around low mass stars as recent Kepler results suggest, M stars are the most likely place to find Earth-like planets in habitable zones.

stars: habitable zones – solar neighborhood
slugcomment: Accepted by the Astronomical Journal, July 2013

1 Introduction

Early astronomers looked to the sky and saw the Moon as a habitable world covered in vast oceans, Venus as a swampy marshland enshrouded in clouds, and Mars with grand canals (Lowell 1895). Not one of these worlds has maintained its promise of abundant life. Instead, the Solar System, once thought to be teeming with life, may be barren, although hope remains for environments under the icy crust of Europa (Marion et al. 2003), in the tiger stripes of Enceladus (Parkinson et al. 2007), in water under the Martian surface (Malin & Edgett 2000), or perhaps lurking somewhere as yet unidentified. With the discovery of more than 700111(May 2013) http://www.exoplanets.org extrasolar planets since 1989, the real estate market in our Solar System is no longer the only place we might look for evidence of life beyond Earth. A likely place to search for planets harboring life is in the habitable zones of nearby stars.

The term “habitable zone” was first coined by Huang (1959) as a region around a star where a planet could support life. Since then, there have been many definitions of habitability, most based on the presence of liquid water on the surface of a planet. These planets could be terrestrial in nature, which are known to exist (Borucki & the Kepler Team 2010), or perhaps moons of gas-giant planets, which are suspected to exist (Weidner & Horne 2010). Examples of nearby stars hosting potentially habitable super-Earths include GJ 581, an M dwarf with potentially two planets in its habitable zone (Mayor et al. 2009; Vogt et al. 2010b) and GJ 667C, another M dwarf with one planet in its habitable zone (Anglada-Escudé et al. 2012).

Kasting et al. (1993) did pioneering work in describing habitable zones (HZs) around main sequence stars. To approximate the location of the HZ, they introduced a one-dimensional climate model that yields the distances from main sequence stars where liquid water would be present, given an initial assumption of a // atmosphere and an Earth-sized planet. They describe the inner boundary of their model as the point at which the atmosphere becomes saturated with , causing a loss of water via photolysis and hydrogen escape; the outer boundary is marked by the formation of clouds that cool a planet’s surface by increasing its albedo and lowering its convective lapse rate. They give an equation for the distance from a star, D, of the HZ in AU based on the incident flux that a planet receives, , the star’s luminosity relative to that of the Sun, and , the ratio of outgoing IR flux to the incoming incident flux at the top of the planet’s atmosphere:

(1)

Using more explicit terms, Equation 1 can be used to show the distance from a star at which a planet would have a given temperature, based on energy balance (Kaltenegger et al. 2002). Equation 2 can then be used to show that the equilibrium temperature, , of a planet at a distance, , from its host star is a function of the stellar effective temperature, , stellar radius, , and the planet’s Bond albedo, . Thus, if the stellar and are known, we can calculate the range of distances where a planet with given albedo222 0.3 for the hypothetical planets used in this paper. would have a surface temperature suitable for liquid water, as described by the planet’s temperature, :

(2)

In this paper, we apply this equation to the nearby population of stars whose stellar properties are well known to estimate the total habitable real estate that they provide. We use the complete sample of all stars currently known to be within 5 pc of the Sun from Henry (2012), and an extended 10 pc sample of AFGK stars, as well as binary properties, photometric and astrometric data. We present our derived and for each star in the sample and discuss the methods used to derive each star’s empirical habitable zone (EHZ). For multiple star systems, we assess dynamical stability to eliminate stellar systems unsuitable for long-term planetary orbits. Our main goal is to determine, as a function of spectral type, the cumulative available EHZ in the solar neighborhood.

2 Motivations for this Study

We do not yet have a detailed understanding of the architectures of all types of planetary systems orbiting various types of stars, although there has been recent progress for planets in close to stars via the Kepler mission (e.g., Howard et al. 2012 for planets in orbital periods less than 50 days around FGKM stars). In this paper we assume no bias in the final locations of planets around stars, including formation and migration (i.e., we assume the distribution of planets to be uniform in semi-major axis), to assess the integrated EHZs of various types of stars found in the solar neighborhood. We focus on the presence of the first habitable planet around a given star, although wider EHZs may of course include more than one planet. This is an important assessment to make given the limited telescope time, funding, and energy of astronomers, so here we focus on the question, “What set of targets might be most appropriate to observe to improve the odds of detecting at least one habitable planet?” This question is posed in wide-ranging arenas, from conversations between students and faculty when developing research projects, to discussions of programmatic directions such as those of NASA’s Exoplanet Program Analysis Group and the NASA/NSF Exoplanet Task Force.

In this paper we evaluate stars within 10 pc in a consistent fashion to assess what spectral types offer the greatest promise for nearby habitable planets. The nearby sample contains stars that have been characterized carefully, and as a population provide the most accurate snapshot of the stellar content of the Galaxy. Thus, this sample provides the foundation for a realistic understanding of the relative merits of examining different types of stars. Our results, coupled with the planet frequency statistics from the Kepler mission, (e.g., Borucki and Koch 2011, Howard et al. 2012, and Dressing and Charbonneau 2013), can provide statistical measures for the of number of habitable planets within larger stellar populations, and particularly among volume-limited samples of nearby stars, as we build to a comprehensive sample of the nearest stars (e.g., Henry et al. 2006; Henry 2012). For example, Howard et al. (2012) show that the number of super-Earth size planets increases with decreasing T for orbital periods less than 50 days. Dressing and Charbonneau (2013) show that for cool stars (T 4000K) the occurrence rate for planets with 0.5–4 R is 0.9 planets per star for orbital periods less than 50 days. They also calculate that the lower limit on the occurrence rate of Earth-size planets in the HZ of cool stars is 0.04 with a 95% confidence. Using the population we describe here, this implies that there could be two Earth-size planets within the EHZs of M dwarfs within 5 pc of the Sun. Assuming a constant density of M dwarfs to 10 pc (not all of which have yet been identified) the number of Earth-size planets jumps to 16. One of the primary motivations of this study is to determine, in aggregate, how the odds of finding such planets around M dwarfs compares to other spectral types.

The results of our habitable real estate calculations, as outlined in this paper, are particularly valuable in highlighting that the ubiquitous M dwarfs provide many locales meeting the canonical definition for habitability. Current searches for habitable worlds orbiting the nearest stars have yielded many Jovian planets and a few terrestrial worlds, but most of the searches to date have been carried out using the radial velocity technique and have focused on bright FGK stars that provide many photons to spectrographs (and which are in the sweet spot for Kepler). For transit searches, M dwarfs provide higher contrast ratios for a given planet, whereas for radial velocity and astrometric searches they provide larger wobbles for a planet than do more massive FGK stars. Knowing that the M dwarfs, as a group, are important stars to search for habitable worlds helps direct our focus back to the solar neighborhood, in which three-quarters of all stars are red dwarfs. Because of their proximity, these stars hold great promise for the detailed characterization of exoplanets.

3 Properties of our Nearest Neighbors

Primary science goals of the Research Consortium on Nearby Stars (RECONS333http://recons.org) and the Center for High Angular Resolution Astronomy (CHARA444http://www.chara.gsu.edu/CHARA/), are to find and determine the fundamental properties of our nearest stellar neighbors. This has led to the most complete assessment to date of stars within 5 pc of the Sun.

3.1 The 5 pc Sample

The modern sample of all known stars and brown dwarfs within 5 pc of the Sun (Henry 2010, 2012), listed in Table 1 (assembled photometry in Table 2) was first published in the Observer’s Handbook 2010. The sample, which is updated yearly, was created using the combination of several ground-based and space-based parallax programs, including the General Catalogue of Trigonometric Stellar Parallaxes (van Altena et al. 1995), Hipparcos (Perryman et al. 1997), RECONS (Henry et al. 1997, 2006; Deacon et al. 2005; Jao et al. 2005; Costa et al. 2005), HST (Benedict et al. 1999, 2002), Gatewood (1989, 1994) and Gatewood et al. (1992, 1993). To be included in the sample, a system must have a weighted mean trigonometric parallax measurement of 200 mas or greater with an error of 10 mas or less. To create this sample the parallaxes compiled were combined and weighted based on the individual measurement errors. The spectral type, with reference, for each star or star system is given with the astrometric data, including RA, Dec, the weighted mean trigonometric parallax, and the number of parallaxes included in the weighted mean, in Table 1. The closing date for the sample is 2012.0.

The 5 pc sample contains 67 stars, including the Sun, and 4 presumed brown dwarfs (spectral types L or T) in 50 systems. Of the 50 systems, 34 are single, 11 are binaries, and 5 are triples, giving a multiplicity fraction of 32%. This fraction is consistent with previous volume limited surveys (35%; Reid & Gizis 1997). The majority (85%) of the sample are main sequence stars; the exceptions include Procyon (GJ 280A), which has a slightly evolved spectral type of F5IV-V, 5 white dwarfs, and the 4 L/T dwarfs. The spectral type breakdown includes 1 A, 1 F, 3 G’s (including the Sun), 7 K’s, 50 M’s, 1 L, 3 T’s, and 5 white dwarfs. We do not include white dwarfs and brown dwarfs in subsequent calculations of habitable real estate, as they are objects that are cooling continually, resulting in unsustainable HZs on long (Gyr) timescales.

3.2 An Estimated 10 pc Sample

Due to the sparse population of all but the M stars in the 5 pc sample, it is difficult to draw meaningful statistics to estimate which stellar spectral types possess the most habitable real estate. Therefore, we extend our sample to 10 pc for A, F, G and K stars. Using the Hipparcos Catalog, which is complete to V=9 (Perryman et al. 1997), we selected all objects with a parallax greater than 100 mas for inclusion into the sample. We expect that the extended 10 pc sample is complete for spectral types A through K, given M=9.0 for a M0.0V star (Henry et al. 2006). However, rather than using spectral type as a selection criterion, we used a color cutoff of 3.5 as the dividing line between K and M dwarfs (Kenyon & Hartmann 1995). As with the 5 pc sample, weighted mean parallaxes from the General Catalogue of Trigonometric Stellar Parallaxes, The Hipparcos Catalog and other sources are listed with the astrometry data for the extended 10 pc sample in Table 3, as well as spectral types and references. Available photometric data are listed in Table 4. We note that there are no O type or B type stars within 10 pc. Because the M star population is not complete out to 10 pc (Henry et al. 2006), we approximate the total M star population by scaling by a factor of eight from the 5 pc sample. For clarity, we refer to the additional AFGK stars from 5-10 pc as the “extended 10 pc sample” and our estimates of all AFGKM stars within 10 pc as the “estimated 10 pc sample”. In total, the stellar population of the estimated 10 pc sample consists of 66 AFGK stars in 57 systems. Broken down by spectral type, the sample contains 4 A stars, 6 F stars, 21 G stars, 35 K stars and an estimated 400 M stars within 10 pc.

3.3 Photometry and Energy Distributions

The photometry used in this paper, listed in Tables 2 & 4, was extracted from sources in the literature with preference given to large surveys and measurements consistent with photometry obtained as part of the CTIO Parallax (CTIOPI) program, which uses the Johnson-Kron-Cousins system. and magnitudes from the USNO-B1.0 catalog (Monet et al. 2003) are incorporated in the extended 10 pc sample and both are rounded to the nearest 0.1 mag. magnitudes are averaged from the first and second epochs.

The majority of photometry is taken from the 2MASS database, identified as those values with errors listed explicitly in Tables 2 and 4 (Cutri et al. 2003). In cases of close binaries with magnitude difference measurements in the literature (e.g., Henry & McCarthy 1993 and Henry et al. 1999), the optical and 2MASS photometry is used with the published magnitude differences to split the component fluxes into individual magnitudes. Note that stars brighter than 5 mag are saturated in 2MASS images and typically have relatively large photometric errors ( 0.2 mag). Where possible, we use measurements in the literature for these stars (Johnson et al. 1966; Johnson et al. 1968; Glass 1975; Mould & Hyland 1976). These magnitudes, listed in their unconverted form in Tables 24 and with specific references listed in the error columns, were then converted to 2MASS magnitudes using color transformations from Carpenter (2001). Of the 16 multiple systems in the 5 pc sample, eight have spatially unresolved photometry in some or all passbands and are marked as “Joint” in the Notes section of Table 2. Similarly, 10 of the 19 multiple systems in the extended 10 pc sample have spatially unresolved photometry in some or all passbands and are listed as “Joint” in the Notes section of Table 4.

4 Methodology to Derive the EHZ

The HZ around a star is primarily a function of the total energy output of a star that reaches the surface of a planet. This can be determined if the stellar temperature and radius are known, which we calculate for our sample of stars as described in Section 4.1. However, a range of other factors, such as atmospheric pressure, composition, and cloud cover play roles in determining the surface temperature of a planet. To account for this, in Section 4.2 we follow previous studies and approximate these effects by using empirical temperature constraints provided by planets in the Solar System.

4.1 SED Fitting used to Derive Stellar Temperature and Radius

Although spectral types are often used to estimate stellar effective temperatures, the various methods for determining spectral types are inhomogeneous and often depend upon the spectral range used. As an alternative, we fit synthetic stellar spectra to broad-band energy distributions to determine effective temperatures and radii. In particular, we use photometric measurements spanning (0.3 to 2.4 m) in conjunction with model spectra generated using the PHOENIX code (Hauschildt et al. 1999). This prescription is only used for single stars and for stars in multiple systems in the 5 pc and extended 10 pc samples with at least four spatially resolved photometric measurements in different filter bandpasses. Estimates for unresolved multiples are discussed in Section 4.3.

These available models span the temperature ranges of of 10,000 K to 7000 K in 200 K increments and 6900 K to 2000 K in 100 K increments. The model spectra have a resolution of 2 Å  and range from 10 Å  to 500 m. The models were convolved with filter responses to create synthetic photometry. For the synthetic photometry, we took zero points from Bessell et al. (1998) and filter responses from CTIO555http://www.ctio.noao.edu/instruments/filters/. filter responses and zero points were from 2MASS666http://www.ipac.caltech.edu/2mass/releases/allsky/doc/. The zero points adopted are listed in Table 5. We adopt log  values of 4.5 or 5.0 for all stars.

Solar metallicity is adopted for all stars except GJ 191 (Fe/H = 0.98; Woolf and Wallerstein 2005) and GJ 451 (Fe/H = 1.16; Valenti and Fisher 2005), for which we adopt metallicities of 1.0. The assumption of solar metallicity for the remainder of our 10 pc sample is based on the 36 FGK stars that overlap with Valenti and Fisher (2005). These stars have an average metallicity of Fe/H = 0.048 with a standard deviation of 0.168 dex.

The flux values in the model spectra are given as a surface flux that must be scaled by a radius to a known distance for fitting with observed integrated flux values. A stellar radius grid from 0.001 R to 3.00 R with a step size of 0.001 R is calculated for each model spectrum. Each spectrum and radius combination is then convolved with filter response and the zero point data referenced above to derive consequent fluxes observed at Earth. These integrated fluxes are then fit via a minimization routine, written in IDL and described in Equation 3, to compare the model flux with the observed flux across each filter bandpass. Here, is the observed integrated flux from the photometric measurements, is the estimated integrated flux from the model grids, is the number of photometric points (degrees of freedom), and is the average error in the photometric measurement. Examples of fits for AFGKM stars in the 5 pc sample are shown in Figure 1.

(3)

The output is an effective temperature from the model and a radius that best fits the measured photometric data. We assume no interstellar extinction for our sample, and choose four photometric points as the minimum number needed to make a fit. When deriving radii, all stars in the sample are assumed to be spherical and radiate isotropically, which is not the case for rapidly rotating stars that may be oblate and experience gravity darkening (e.g., Altair, see Monnier et al. 2007; Vega, see Aufdenberg et al. 2006). This is most common among stars earlier than mid-F spectral type, as these stars are fully radiative and consequently do not possess an efficient rotational braking mechanism (e.g., Wilson 1965). However, all but one early type star (i.e., earlier than spectral type F5) within 10 pc have projected rotational velocities less than 100 km/s, which correspond to projected oblateness values 2% (Absil et al. 2008). These apparently slow rotating stars include Sirius A (GJ 244, A1V, 16 km/s; Royer 2002), Procyon A (GJ 280, F5V-IV, 4.9 km/s; Fekel 1997), Vega (GJ 721, A0V, 24 km/s; Royer 2007), and Fomalhaut (GJ 881, A4V, 93 km/s; Royer et al. 2007). We note that despite having a small sin value, Vega is believed to be rapidly rotating with a nearly pole on orientation (Aufdenberg et al. 2006). An additional rapidly rotating star is Altair (GJ 768, A7V, 217 km/s; Royer 2007) which has an oblateness of 18% determined from interferometric measurements by the CHARA Array (Monnier et al. 2007). As expected, our derived radii and effective temperatures for Altair and Vega are intermediate to the polar and equatorial values listed in Monnier et al. (2007) and Aufdenberg et al. (2006), respectively. Because the EHZ boundaries are a function of the square root of the total luminosity (see Section 4.2), our adopted methodology should yield reliable estimates of the habitable real estate these stars provide, even if the stellar temperatures vary with stellar latitude.

As a consequence of the limited temperature resolution of the PHOENIX grids used (T=200K from 10000K to 7000K and T=100K from 6900K to 2000K), the fitting routine can determine a slightly larger radius coupled with a cooler temperature, or vice versa. Systematic uncertainties in the PHOENIX models are such that a T of less than 100K are unreliable (Hauschildt, priv. comm.). As the Stefan-Boltzmann law shows RTL, the luminosity determined from the SED remains the same as long as the radii and effective temperatures move in opposite directions, and therefore the EHZ, being a function of the square root of the luminosity, does not change. Of key importance, the output radii and temperatures determined here allow us to compare our results directly to those found via interferometric techniques.

Of the stars investigated, 28 have spatially resolved angular diameters from long baseline interferometric instruments such as CHARA, PTI, and VLTI (Table 6). Fifteen of these measurements are from the recent effort of Boyajian et al. (2012). Because these measurements determine sizes to within a few percent, we use them to test the accuracy of the radii determined in our fitting process. The published radii are on average 7.4% larger than our derived radii, which shows a systematic effect. Our derived model are on average 2.4% hotter than derived from interferometric measurements. A comparison of our model versus published values is shown in Figure 2. The temperature uncertainties correspond to spectral type uncertainties of 1-2 spectral subclasses, similar to the error associated with most spectral classification methods. As the average values indicate, the overprediction of temperature leads to the expected under-prediction of radius, and the combination yields a more accurate luminosity, and thus consistent EHZ. Given this agreement, we adopt our model values for T and R/R in final calculations of the habitable real estate.

A few stars are worthy of note. Procyon is slightly evolved (F5.0IV-V) and has a highly constrained log  of 4.050.04 (Fuhrmann et al. 1997) measured via high resolution spectroscopy in concert with masses determined using astrometry from the Procyon-white dwarf orbit. We adjusted the log  to 4.0 for this star and recomputed the and . This, nevertheless, yielded identical values within the model grid resolution as those of log =4.5. The model spectra used in this work have a low temperature limit of 2000 K, which is the value derived for the three intrinsically faintest stars in this sample: SCR 1845-6357A (M8.5V), DEN 1048-3956 (M8.5V), and LP 944-020 (M9.0V).

4.2 Habitable Zones of Single Stars

Kasting et al. (1993) use a one-dimensional climate model to calculate HZs around single main sequence stars. A one-dimensional climate model characterizes a planet’s global temperature by dividing the planet into latitudinal bands, and treats the planet as uniform with respect to longitude. These one-dimensional radiative-convective models are a good approximation of global temperature, but more complicated 3-D global climate models are needed to account for the complex physical interactions associated with oceans, clouds, and land surface processes. These inputs add parameters such as land/ocean surface coverage and clouds, which can vary from planet to planet, complicating the overall goal to characterize the EHZ of a star. Here we use the one-dimensional model to generalize the EHZ, and adopt a modified version of the one-dimensional model based on the “Venus and early Mars criterion” from Selsis et al. (2007). In that work, they argue that empirical evidence shows that Venus has not had water on its surface for at least one billion years, and Mars had water on its surface around 4 billion years ago. The solar fluxes at those times were 8% and 28% lower, respectively (Baraffe et al. 1998). Venus (0.72 AU today) and Mars (1.52 AU today) would need to be at distances of 0.75 AU and 1.77 AU, respectively, to receive these levels of solar flux today.

Selsis et al. (2007) provide a method for estimating the inner and outer edges of HZs for stars with T = 3700K-7200K. The stars in the sample discussed here range in temperatures from 2000K to 10000K. We have therefore chosen to derive new relations for the HZ boundaries that span the entire stellar temperature regime of our sample, and thereby provide a consistent methodology for all stars in the sample.

In defining our EHZ inner and outer boundaries, we assume a planet with an atmosphere, radius, mass, and Bond albedo (0.3) that matches Earth (Kasting 1996). This leads to the EHZ Equations 4 and 5, used to determine the empirical surface temperature of an Earth-like planet that satisfies the “Venus criterion” (we adopt 0.80 AU on the suggestion of Kasting, priv. comm.) and “Mars criterion” (1.77 AU). The resulting inner and outer radii of the EHZ correspond to equilibrium temperatures of 285 K to 195 K, respectively.

(4)
(5)

Note that these only depend on R and T, or essentially the square root of the star’s luminosity. Values for both samples are listed in Tables 7 and 8. Only stars used in the cumulative EHZ calculations are listed, except for the cases of Sirius (GJ 244A) and Procyon (GJ 280A), which provide useful benchmarks.

4.3 Habitable Zones of Multiple Star Systems

Although stars in multiple systems are often avoided in planet searches, planets have been found in binary and multiple systems (e.g. Patience et al 2002; Raghavan et al. 2006; Eggenberger et al. 2007). The potentially dynamically disruptive effects of any close stellar companion must be considered when assessing the possibility of formation, long-term dynamical stability, and ultimately the habitability of planets in multiple star systems. The Centauri triple system, at a distance from the Sun of 1.34 pc for the G2V-K0V pair (GJ 559 AB) and 1.30 pc for the wide M5V companion (GJ 551), includes the nearest set of Sun-like stars, and provides a test case to study the habitability of multiple stars. The G-K pair has an orbit with a semimajor axis of 1757 and eccentricity of 0.518 (Pourbaix et al. 2002). This gives periastron and apastron distances of 11.33 AU and 26.67 AU, respectively. Barbieri et al. (2002) show for Centauri A that planets can form in stable orbits on a timescale of 5 Myr. Using numerical simulations, they show that not only could planets form, but in some models they formed directly in the habitable zone. Quintana et al. (2007) similarly find that binary separations greater than 10 AU did not inhibit the formation of terrestrial planets at 2 AU. Consistent with this, Wiegert & Holman (1997) show that the orbit of a planet can be stable as long as the ratio of the semimajor axis of the binary to that of the planet is more than 5:1.

The 36 multiple systems in the 5 pc and extended 10 pc samples consist of 27 binaries, 6 triples, and 3 quadruple systems (GJ 423, GJ 570, and GJ 695), for a total of 84 stars/brown dwarfs. However, nine are not main sequence stars, and excluded because of their evolutionary states (e.g., sub-giants, white dwarfs, and brown dwarfs). Additionally, 16 are M star companions in the extended 10 pc AFGK sample. Because the habitable real estate of M stars out to 10 pc is estimated by scaling the 5 pc results, we do not consider these M stars in our EHZ calculations. This leaves 59 stars in multiple systems with potential habitable zones. For clarity, we emphasize that the EHZ of each star in a system is calculated separately.

Of the 59 stars, 43 (73%) have at least 4 spatially resolved photometric measurements in different filter bandpasses. For these stars, the same prescription used in Section 4.2 is used to calculate the EHZs. For the 16 stars that are not photometrically spatially resolved from their nearest companion(s), we estimate the EHZ locations based on spectral type information for the components. Using the assembled spectral types listed in Tables 1 & 3, we estimate the components’ color using the spectral type versus colors relations of Kenyon & Hartmann (1995), and estimate the location of the EHZs using the relations described in Section 5.2.

To assess the dynamical stability of any planets in these EHZs, we compare the locations of the outer EHZ boundaries to the binary separations listed in Table 9. We consider a planet to be dynamically stable if the periastron distance of a star’s nearest companion is greater than five times the outer EHZ boundary. In cases where the periastron distance can not be calculated (because its full orbit solution is not known), we use the projected separation. Fortunately, these exceptions are all large separation multiples, and thus minor errors in the adopted separation are likely irrelevant for dynamical stability considerations. The ratios of periastron distances to outer EHZ boundaries are illustrated in Figure 3. For each star and its nearest companion, the ratios range from 0.001 to 164107. 49 of the 59 stars have ratios greater than 5 to their nearest companions, and thus EHZs in which planets should be in dynamically stable orbits. The remaining 10 stars (GJ 53A, GJ 222A, GJ 244A, GJ 280A, GJ 423A, GJ 423B, GJ 713A, GJ 713B, GJ 866A, and GJ 866C) are considered to have EHZs in which planets would not be in dynamically stable orbits, so are excluded in our estimate of total EHZ real estate. Seven of these have ratios less than 1.0, hinting at the possibility of circumbinary planets. However, the majority of the EHZ outer radii are only a few times the binary separations, making it unlikely that these systems would have dynamically stable circumbinary planets in the EHZ. Nonetheless, it is worth noting that a few massive planets have been reported in circumbinary orbits (Lee et al. 2009; Qian et al 2010).

5 Discussion

The described HZ calculations are used to assess the total habitable real estate in the solar neighborhood and to determine the amount of habitable real estate as a function of spectral type. Evolved stars, brown dwarfs, and multiple stars with separations detrimental to the orbital stability of a planet in the EHZ, as described above, are excluded in these assessments. In the 5 pc sample, stars removed from the analysis due to close companions include GJ 244A, GJ 244B, GJ 280A, GJ 280B, GJ 866A, and GJ 866C. The distribution by spectral type, after the removal of these stars in the 5 pc sample is as follows: 0 A, 0 F, 3 G, 7 K, and 48 M stars. Similarly, stars removed from the extended 10 pc sample analysis due to close companions include GJ 53A, GJ 53B, GJ 222A, GJ 222B, GJ 423A, GJ 423 B, GJ 423C, GJ 423D, GJ 713A, and GJ 713B. Stars with evolved spectral types such as GJ 150, GJ 695A, and GJ 780 are also removed from subsequent calculations. By spectral type, the total stellar samples considered in the final EHZ assessment are 3 A, 4 F, 14 G, 34 K, and an estimated 384 M stars.

5.1 The EHZ “Width”

Using our initial assumptions of a terrestrial “Earth-like” planet as the basis for our EHZ, we estimate the habitable real estate using linear AU separations from the central star, essentially the width of the EHZ. In Table 10 we present the EHZ width totals for each spectral type in the 5 pc and total 10 pc samples.

The cumulative EHZ width for stars in the 5 pc subsample is 8.8 AU, including 2.6 AU for the 3 G stars (including the Sun) and 2.9 AU for the 7 K stars. The 48 M dwarfs in the 5 pc sample en masse provide 3.3 linear AU available for habitable planets, or 38% of the available EHZ. The dominant contribution of M dwarfs to the EHZ width is demonstrated clearly using the estimated 10 pc sample. The total EHZ width for the estimated 10 pc sample is 71.5 AU, including 13.2 AU for the 3 A, 4.9 AU for the 4 F stars, 11.9 AU for the 14 G stars, and 15.4 AU for the 34 K stars. The estimated 384 M stars en masse provide 26.1 AU of linear EHZ. This accounts for 36.5% of the total EHZ. Thus, by spectral type, M stars en masse provide the largest EHZ real estate.

5.2 Predicting the Size of the Habitable Zone from Colors

Given the rapid pace of exoplanet discovery, it would be helpful to have a tool to easily and accurately predict the location of the EHZ to determine whether or not a planet resides within it. Predicting the EHZ of a star based on spectral classification can be problematic due to the inhomogeneity in classification and spectral types being determined over different wavelength ranges. As shown in Henry et al. (2006), the color is a useful temperature diagnostic for the A through M stars that dominate the solar neighborhood. This relation can also be very helpful in determining a rough estimate of the EHZ based on observable photometry, and may be easily scaled to larger populations.

We use the results from the 5 pc and extended 10 pc samples to derive a relation between color and the size and location of the EHZ. As in the computation of total habitable real estate, we removed binary stars with unresolved photometry, as well as stars known to be evolved. We do, however, use stars such as Sirius (GJ 244) and Procyon (GJ 280) for which EHZs have been determined, even though their companions corrupt their EHZs. Their white dwarf companions do not significantly contribute to their luminosities or , and their inclusion improves the statistics of our fit. We fit a second order polynomial, described by Equation 6, to the colors and computed EHZ widths shown in Figure  4.

(6)

Using the same method, a relationship for color and the inner and outer radii of the EHZs are described by Equations 7 and 8, respectively. These relations are only valid for main sequence stars.

(7)
(8)

As a check on these relations, we use these to calculate the total EHZ width by spectral type of the estimated 10 pc sample and compare these values to the direct calculations described in Sections 4.2 & 4.3. We find the total EHZ widths from the empirical relations differ on average from the calculated total widths by 12.7%, 6.4%, 1.6%, 4.7%, and 0.3% for A, F, G, K, and M stars respectively; negative values correspond to underpredictions of the EHZ width totals. The higher percentage differences for A type and F type totals are due to the relatively small populations within 10 pc and the effects of large 2MASS photometric errors due to brightness. The results imply that this relation is useful for quickly estimating the amount of habitable real estate for a population with known values. We also test how well the predicted inner and outer boundaries from our relations agree for any given star. On average, these predictions yield values consistent to 3% with a dispersion of 22% for both inner and outer boundaries for AFGKM stars in our samples. These dispersions can be interpreted as the uncertainty in the locations of these boundaries from these relations.

5.3 Planets in the EHZs of Nearby Stars

Of the 14 confirmed planetary systems within 10 pc of the Sun for which orbits have been determined, five contain multiple planets (GJ 139, GJ 506, GJ 581, GJ 667C, and GJ 876). All 14 systems are listed in Table 11 with published values for semimajor axis and eccentricity, as well as calculated inner and outer radii of the EHZ from this work. Three of the systems, GJ 581, GJ 667C, and GJ 876 have planets in the EHZ.

GJ 581, an M2.5V star at a distance of 6.25 pc, has six proposed planets, but the existence of GJ 581g and GJ 581f are currently debated (see: Vogt et al. 2010; Andrae et al. 2010; Gregory 2011; Anglada-Escudé 2010; Tuomi 2011). If real, GJ 581g, with a semimajor axis of 0.146 AU, orbits in the EHZ in a presumed circular orbit. Using the CHARA Array, von Braun et al. (2011) recently measured the size of the star and derived HZ boundaries of R= 0.11 AU and R= 0.21 AU. Our EHZ is somewhat closer in to the star, R= 0.083 AU and R= 0.179 AU, but still places GJ 581g in the EHZ. The differences are due to the our calculated luminosity (L= 0.11) being 8% lower than von Braun et al. (2011), as they adopted an extinction of A= 0.174 for GJ 581, which they note as unexpected for a star at this distance. GJ 581d, with semimajor axis of 0.22 AU and eccentricity of 0.38, also moves in and out of the EHZ of GJ 581.

GJ 667C, an M1.5V star at a distance of 7.23 pc, hosts two planets, and possibly four (Anglada-Escudé et al. 2012). Although GJ 667Cb does not lie within the EHZ, GJ 667Cc ( sin  of 4.5 ) lies within the EHZ for the majority of its orbit. With a semimajor axis of 0.123 AU and eccentricity 0.27, it may lie completely within the EHZ once the eccentricity is more highly constrained.

GJ 876, an M3.5V star at a distance of 4.66 pc, hosts four planets (Rivera et al. 2010). Our calculations show an EHZ spanning 0.090-0.191 AU. Rivera et al. (2010) report orbital fits for two planets near the EHZ with semimajor axes of 0.13 AU (GJ 876c) and 0.21 AU (GJ 876b), and eccentricities of 0.25 and 0.03, respectively. As shown in Figure 5, this allows for GJ 876c to be in the EHZ of its host star for the full duration of its orbit, while GJ 876b lies just outside the EHZ. Although these planets are not considered terrestrial ( sin  of 0.56 and 1.89 ), the possibility exists that they could have terrestrial-like moons that could be habitable.

5.4 Complications to Habitability

The previous sections provide estimates of EHZs based on the requirement of liquid water on a planetary surface. Of course, a planet’s location in the EHZ of a host star does not guarantee its habitability. A host of other factors, such as planet size, atmosphere, magnetic fields, and even plate tectonics, play vital roles in determining the habitability of a planet in the EHZ. Without a sufficiently thick atmosphere, biologically harmful radiation can penetrate to the surface of a planet. On Earth, atmospheric levels are kept in check by the carbon-silicate cycle. Known to regulate climate temperatures through a negative feedback, this cycle allows for as much as 60 bars (Kasting 1996) of to be locked away in rock and sediments. This slow carbon-silicate cycle requires that water be present, because without water, the atmospheric cannot be sequestered as carbonate. A magnetosphere on Earth also plays an important role by deflecting harmful charged particles. Tectonic activity may be one of the key factors in keeping a planet habitable (Doyle et al. 1998). Without water, the lithosphere of a planet may become a stagnant lid, halting tectonic activity and the sequestration of .

There is a temporal constraint on habitability as well, as the HZ may change considerably over the lifetime of a star (Kasting et al. 1993; Kasting 1996; Tarter et al. 2007; Selsis et al. 2007). Putting these complications aside, the requirement of liquid water on the surface of a planet is a good first order approximation to habitability.

6 Summary

We assess the sample of stars currently known to be within 5 pc of the Sun for the purpose of determining the habitable real estate and its dependence on spectral type. Because of the sparse population of high mass stars within 5 pc of the Sun, we expand this sample for AFGK stars to 10 pc; there are no O or B stars within 10 pc of the Sun. After eliminating evolved stars, substellar objects, and close multiples in which planets in HZs would be dynamically unstable, we use the final sample to estimate the EHZs for stars in both the 5 pc and extended 10 pc samples. We do not consider circumbinary habitable zones in this work, but EHZs are calculated in the same fashion as single stars for each of the 49 components in multiple systems that satisfy our dynamical stability constraint.

Using PHOENIX models convolved with filter response curves, we fit observed photometry for each object, assuming spherical, non-rapidly rotating stars with solar metallicity and log  values of 4.0 to 5.0, with the 2 exceptions being the metal poor stars GJ 191 and GJ 451. This fitting process allows us to determine a radius and for each star that is then used to determine its surrounding EHZ, calculated using a modified “Venus and early Mars criterion” from Selsis et al. (2007).

We use estimates of linear AU to map the EHZ of each star and sum by spectral type en masse: 48 M dwarf stars used in the 5 pc sample provide more habitable real estate (3.3 AU) than the three G dwarfs stars (2.6 AU) and seven K stars (2.9 AU) found within 5 pc of the Sun. Even after extending the sample of AFGK stars to 10 pc, the anticipated sample of M dwarfs within 10 pc (not all have yet been identified) possess more EHZ real estate than any other spectral type, spanning 26 AU compared to 13.2 AU, 11.9 AU, and 15.4 AU for each of the A, G, and K types (the F stars provide only 4.9 linear AU of EHZ). The result is a natural consequence of the large relative numbers of M dwarfs, and the frequency of close companions that declines with mass.

As a population M dwarfs provide more options and more habitable real estate than their more massive counterparts. Furthermore, recent results from Kepler show that for stars with T¿4000K within 5 pc of the Sun, there is likely to be at least 2 Earth-size planets in the HZ. That number increases to 16 within 10 pc (Dressing & Charbonneau 2013).

Using the 5 pc and extended 10 pc samples, we derive relations between color and EHZ width and inner and outer limits. Comparisons of color predicted locations suggest they are comparable to uncertainties associated with habitability assumptions (e.g., Section 4.2). Thus, these color relations are practical tools for estimating the EHZs of stars using commonly available photometric measurements. The relations for the inner and outer radii of the EHZ are helpful for quickly estimating whether or not a known planet or disk is within the EHZ. The relation for EHZ size is useful in predicting the habitable real estate available in a stellar population. In particular, we consider the results for the 14 extrasolar planetary systems known within 10 pc of the Sun. The three systems with planets in the calculated EHZs — GJ 581, GJ 667C, and GJ 876 — are all M dwarfs. In total, as many as four planets circling these stars spend at least part of their time in the EHZs, providing an ideal set of targets for future efforts to detect biosignatures.

6.1 Acknowledgments

The authors would like to thank J. Kasting for extremely helpful advice and guidance. We would also like to thank the RECONS team for the generous amount of data and support provided. Data used in this paper were acquired via support from the National Science Foundation (grants AST 05-07711 and AST 09-08402) and through the continuous cooperation of the SMARTS Consortium. This project was funded in part by NSF/AAG grant no. 0908018. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France, data from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and IPAC, funded by NASA and NSF, and the Sixth Catalog of Orbits of Visual Binary Stars, operated by the US Naval Observatory.

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Figure 1: Examples of model () and observed () flux values are shown for (top-left to right) GJ 244A (A1.0V), GJ 280A (F5.0IVV), (middle-left to right) GJ 599A (G2.0V), GJ 380 (K7.0V), (bottom-left to right GJ 273 (M3.5V), SCR 1845-6357A (M8.5V). In each case the points represent photometry. Model values for stars with incomplete photometry, e.g., GJ 559A missing UJHK and SCR 1845-6357A missing UB, are plotted for completeness.
Figure 2: Model fits vs published values. The solid line illustrates 1:1 agreement and the dashed lines represent 10% offsets. Error bars are 1 for the model and given errors for the interferometrically derived values used to derive the published values.
Figure 3: The closest approach of a companion star to the outer radius of the EHZ is plotted versus the primary’s - value. Photometrically unresolved multiples are plotted as open squares, while resolved components are plotted as filled circles. Stars with companions that get closer than 5 times the outer EHZ boundary (dashed line) are considered dynamically unstable planet hosts, and are not included in the total habitable real estate calculations. GJ 663AB and GJ 663BA are plotted as the same point as their V and K = 0. The open square at = 8.88, ratio = 173, is SCR 1845-6357, an M dwarf with a brown dwarf companion in a highly uncertain orbit.
Figure 4: Empirical habitable zone (EHZ) widths for the 5 pc (filled circles) and extended 10 pc samples (open squares). The best fit relation (Equation 6 in text) is overplotted.
Figure 5: The EHZ in this figure is shown as a shaded disk, along with the orbits of the two planets (dotted circles) in the GJ 876 system nearest the EHZ.
Name LHS RA 2000.0 DEC err of SpType Ref
Sun G2.0V
GJ 1 1 00 05 24.4 37 21 27 .23032 .00090 2 M1.5V Hen10
GJ 1002 2 00 06 43.2 07 32 17 .21300 .00360 1 M5.0V Hen94
GJ 15 A 3 00 18 22.9 44 01 23 .27987 .00060 3 M1.5V Hen94
GJ 15 B 4 00 18 22.9 44 01 23 .27987 .00060 3 M3.5V Hen94
GJ 35 7 00 49 09.9 05 23 19 .23270 .00181 2 DZ7 YPC95
GJ 54.1 138 01 12 30.6 16 59 57 .26908 .00299 2 M4.5V Hen94
GJ 65 A 9 01 39 01.3 17 57 01 .37370 .00270 1 M5.5V Hen94
GJ 65 B 10 01 39 01.3 17 57 01 .37370 .00270 1 M6.0V Hen94
GJ 71 146 01 44 04.1 15 56 15 .27397 .00017 2 G8.5V Gra06
GJ 83.1 11 02 00 13.2 13 03 08 .22480 .00290 1 M4.5V Hen94
SO 02531652 02 53 00.9 16 52 53 .25941 .00089 3 M7.0V Hen04
DEN 0255-4700 02 55 03.7 47 00 52 .20137 .00389 1 L7.5V Cos06
GJ 144 1557 03 32 55.8 09 27 30 .31122 .00009 3 K2.0V Gra06
GJ 1061 1565 03 36 00.0 44 30 46 .27201 .00130 2 M5.0V Hen06
LP 944-020 03 39 35.2 35 25 41 .20140 .00421 1 M9.0V Sch07
GJ 166 A 23 04 15 16.3 07 39 10 .20065 .00023 2 K0.5V Gra06
GJ 166 B 24 04 15 22.0 07 39 35 .20065 .00023 2 DA4 CNS91
GJ 166 C 25 04 15 22.0 07 39 35 .20065 .00023 2 M4.5V Hen94
GJ 191 29 05 11 40.6 45 01 06 .25567 .00091 2 M2.0VI Jao08
GJ 234 A 1849 06 29 23.4 02 48 50 .24444 .00092 3 M4.0V Mon01
GJ 234 B 1850 06 29 23.4 02 48 50 .24444 .00092 3 M5.5V Rei04
GJ 244 A 219 06 45 08.9 16 42 58 .38002 .00128 2 A1.0V Joh53
GJ 244 B 06 45 08.9 16 42 58 .38002 .00128 2 DA2 CNS91
GJ 273 33 07 27 24.5 05 13 33 .26623 .00066 3 M3.5V Hen94
GJ 280 A 233 07 39 18.1 05 13 30 .28517 .00064 4 F5.0IVV Gra01
GJ 280 B 07 39 18.1 05 13 30 .28517 .00064 4 DA CNS91
GJ 1111 248 08 29 49.5 26 46 37 .27580 .00300 1 M6.0V Rei95
GJ 380 280 10 11 22.1 49 27 15 .20553 .00049 2 K7.0V Hen94
GJ 388 5167 10 19 36.4 19 52 10 .20460 .00280 1 M3.0V Hen94
LHS 288 288 10 44 21.2 61 12 36 .20970 .00265 2 M5.5V Hen04
LHS 292 292 10 48 12.6 11 20 14 .22030 .00360 1 M6.5V Rei95
DEN 1048-3956 10 48 14.6 39 56 07 .24853 .00118 3 M8.5V Hen04
GJ 406 36 10 56 29.2 07 00 53 .41910 .00210 1 M6.0V Hen94
GJ 411 37 11 03 20.2 35 58 12 .39325 .00057 2 M2.0V Hen94
GJ 412 A 38 11 05 28.6 43 31 36 .20567 .00093 2 M1.0V Hen94
GJ 412 B 39 11 05 30.4 43 31 18 .20567 .00093 2 M5.5V Hen94
GJ 440 43 11 45 42.9 64 50 29 .21612 .00109 3 DQ6 CNS91
GJ 447 315 11 47 44.4 00 48 16 .29814 .00137 2 M4.0V Hen94
GJ 473 A 333 12 33 17.2 09 01 15 .22790 .00460 1 M5.0V Hen10
GJ 473 B 12 33 17.2 09 01 15 .22790 .00460 1 M7.0V CNS91
GJ 551 49 14 29 43.0 62 40 46 .76885 .00029 4 M5.0V CNS91
GJ 559 A 50 14 39 36.5 60 50 02 .74723 .00117 1 G2.0V Gra06
GJ 559 B 51 14 39 35.1 60 50 14 .74723 .00117 1 K0.0V CNS91
GJ 628 419 16 30 18.1 12 39 45 .23438 .00150 2 M3.0V Hen94
GJ 674 449 17 28 39.9 46 53 43 .22011 .00139 2 M2.5V Mon01
GJ 687 450 17 36 25.9 68 20 21 .22047 .00083 2 M3.0V Hen94
GJ 699 57 17 57 48.5 04 41 36 .54551 .00029 2 M4.0V Hen94
GJ 725 A 58 18 42 46.7 59 37 49 .28383 .00146 3 M3.0V Hen94
GJ 725 B 59 18 42 46.9 59 37 37 .28383 .00146 3 M3.5V Hen94
SCR 1845-6357 A 18 45 02.6 63 57 52 .25950 .00111 2 M8.5V Hen04
SCR 1845-6357 B 18 45 02.6 63 57 52 .25950 .00111 2 T5.5V Bil06
GJ 729 3414 18 49 49.4 23 50 10 .33722 .00197 2 M3.5V Hen10
GJ 1245 A 3494 19 53 54.2 44 24 55 .22020 .00100 1 M5.5V Hen94
GJ 1245 B 3495 19 53 55.2 44 24 56 .22020 .00100 1 M6.0V Hen94
GJ 1245 C 19 53 54.2 44 24 55 .22020 .00100 1 M7.0V Rei04
GJ 820 A 62 21 06 53.9 38 44 58 .28608 .00048 3 K5.0V Hen94
GJ 820 B 63 21 06 55.3 38 44 31 .28608 .00048 3 K7.0V Hen94
GJ 825 66 21 17 15.3 38 52 03 .25344 .00080 2 M0.0V Tor06
GJ 832 3685 21 33 34.0 49 00 32 .20203 .00100 2 M1.5V Joh10
GJ 845 A 67 22 03 21.7 56 47 10 .27607 .00028 2 K4.0V Gra06
GJ 845 B 22 04 10.5 56 46 58 .27607 .00028 2 T1.0V McC04
GJ 845 C 22 04 10.5 56 46 58 .27607 .00028 2 T6.0V McC04
GJ 860 A 3814 22 27 59.5 57 41 45 .24806 .00139 2 M3.0V Hen94
GJ 860 B 3815 22 27 59.5 57 41 45 .24806 .00139 2 M4.0V Hen94
GJ 866 A 68 22 38 33.4 15 18 07 .28950 .00440 1 M5.0V Hen02
GJ 866 B 22 38 33.4 15 18 07 .28950 .00440 1 M
GJ 866 C 22 38 33.4 15 18 07 .28950 .00440 1 M
GJ 876 530 22 53 16.7 14 15 49 .21447 .00057 3 M4.0V Mon01
GJ 887 70 23 05 52.0 35 51 11 .30508 .00070 2 M2.0V Tor06
GJ 905 549 23 41 55.0 44 10 38 .31637 .00055 3 M5.5V Hen94

Note. –
Bil06 Biller et al. (2006)
CNS91 Catalog of Nearby Stars, Gliese & Jahreiss (1991)
Cos06 Costa et al. (2006)
Gra01 Gray et al. (2001)
Gra06 Gray et al. (2006)
Hen94 Henry et al. (1994)
Hen02 Henry et al. (2002)
Hen04 Henry et al. (2004)
Hen06 Henry et al. (2006)
Hen10 Henry et al. (2010)
Jao08 Jao et al. (2008)
Joh53 Johnson & Morgan (1953)
Joh10 Johnson et al. (2010)
McC04 McCaughrean et al. (2004)
Mon01 Montes et al. (2001)
Rei95 Reid et al. (1995)
Rei04 Reid et al. (2004)
Sch07 Schmidt et al. (2007)
Tor06 Torres et al. (2006)
YPC95 Yale Parallax Catalog, van Altena et al. (1995)

Table 1: Five Parsec Sample
Name U Uref B Bref V Vref R Rref I Iref J err H err K err Notes
Sun 25.97 Alo95 26.10 Alo95 26.75 Alo95 27.27 Alo95 27.56 Alo95 27.928 Alo95 28.211 Alo95 28.274 Alo95
GJ 1 10.02 Bes90 8.54 Bes90 7.57 Bes90 6.41 Bes90 5.328 0.019 4.828 0.076 4.523 0.017
GJ 1002 17.61 Leg92 15.73 Wei96 13.77 Bes91 12.16 Bes91 10.15 Bes91 8.323 0.019 7.792 0.034 7.439 0.021
GJ 15 A 10.87 Leg92 9.63 Leg92 8.08 Leg92 5.94 Leg92 5.252 0.264 4.476 0.200 4.018 0.020
GJ 15 B 14.26 Leg92 12.88 Wei96 11.06 Wei96 9.83 Wei96 8.24 Wei96 6.789 0.024 6.191 0.016 5.948 0.024
GJ 35 12.94 Bes90 12.40 Bes90 12.14 Bes90 11.91 Bes90 11.688 0.022 11.572 0.024 11.498 0.025
GJ 54.1 15.24 Leg92 13.95 Bes90 12.10 Bes90 10.73 Bes90 8.95 Bes90 7.258 0.020 6.749 0.033 6.420 0.017
GJ 65 A 14.96 Leg92 13.95 Bes90 12.61* Hen99 10.40 Bes90 8.34 Bes90 6.86* Hen93 6.30* Hen93 5.91* Hen93 joint UBRI
GJ 65 B 13.06* Hen99 7.24* Hen93 6.60* Hen93 6.31* Hen93
GJ 71 4.42 Joh66 4.21 Bes90 3.49 Bes90 3.06 Bes90 2.67 Bes90 2.06 Joh66 1.800 0.234 1.68 Joh66
GJ 83.1 15.47 Leg92 14.14 Bes90 12.31 Bes90 10.95 Bes90 9.21 Bes90 7.514 0.017 6.970 0.027 6.648 0.017
SO 02531652 15.13 Hen06 13.03 Hen06 10.65 Hen06 8.394 0.027 7.883 0.040 7.585 0.046
DEN 0255-4700 22.92 Cos06 19.90 Cos06 17.45 Cos06 13.246 0.027 12.204 0.024 11.558 0.024
GJ 144 4.61 Bes90 3.73 Bes90 3.22 Bes90 2.79 Bes90 2.20 Gla75 1.75 Gla75 1.65 Gla75
GJ 1061 13.09 Hen06 11.45 Hen06 9.46 Hen06 7.523 0.020 7.015 0.044 6.610 0.021
LP 944-020 13.29 Dea07 10.725 0.021 10.017 0.021 9.548 0.023
GJ 191 10.41 Bes90 8.85 Bes90 7.90 Bes90 6.90 Bes90 5.821 0.025 5.316 0.027 5.049 0.021
GJ 234 A 14.03 Leg92 12.81 Bes90 11.18* Hen99 9.78 Bes90 8.08 Bes90 6.57* Hen93 5.97* Hen93 5.73* Hen93 joint UBRI
GJ 234 B 14.26* Hen99 8.36* Hen93 7.60* Hen93 7.23* Hen93
GJ 244 AB 1.4 1 Joh66 1.43 Bes90 1.43 Bes90 1.42 Bes90 1.41 Bes90 1.391 0.109 1.391 0.184 1.390 0.214 joint
GJ 273 12.59 Wei93 11.42 Bes90 9.85 Bes90 8.70 Bes90 7.16 Bes90 5.714 0.032 5.219 0.063 4.857 0.022
GJ 280 AB 0.82 Joh66 0.79 Bes90 0.37 Bes90 0.12 Bes90 0.12 Bes90 0.40 Gla75 0.60 Gla75 0.65 Gla75 joint
GJ 1111 16.95 Bes90 14.90 Bes90 12.90 Bes90 10.64 Bes90 8.235 0.021 7.617 0.018 7.260 0.024
GJ 380 9.25 Leg92 7.97 Leg92 6.59 Leg92 5.74 Leg92 4.97 Leg92 3.98 Gla75 3.32 Gla75 3.19 Gla75
GJ 388 11.91 Leg92 10.85 Leg92 9.32 Leg92 8.23 Leg92 6.81 Leg92 5.449 0.027 4.843 0.020 4.593 0.017
LHS 288 13.92 Bes91 12.33 Bes91 10.31 Bes91 8.492 0.021 8.054 0.044 7.728 0.027
LHS 292 17.70 Leg92 15.73 Bes91 13.67 Bes91 11.33 Bes91 8.857 0.021 8.263 0.036 7.926 0.033
DEN 1048-3956 17.39 Jao05 15.05 Jao05 12.55 Jao05 9.538 0.022 8.905 0.044 8.447 0.023
GJ 406 17.03 Leg92 15.52 Bes90 13.53 Bes90 11.67 Bes90 9.50 Bes90 7.085 0.024 6.482 0.042 6.084 0.017
GJ 411 10.12 Leg92 8.98 Leg92 7.47 Leg92 6.46 Leg92 5.32 Leg92 4.13 Gla75 3.56 Gla75 3.20 Gla75
GJ 412 A 11.48 Leg92 10.34 Wei96 8.77 Wei96 7.79 Wei96 6.70 Wei96 5.538 0.019 5.002 0.021 4.769 0.020
GJ 412 B 16.53 Bes90 14.44 Bes90 12.77 Bes90 10.68 Bes90 8.742 0.025 8.177 0.024 7.839 0.026
GJ 440 11.04 Lan92 11.68 Lan92 11.50 Sub09 11.34 Sub09 11.20 Sub09 11.188 0.024 11.130 0.025 11.104 0.026
GJ 447 14.22 Leg92 12.92 Bes90 11.16 Bes90 9.85 Bes90 8.17 Bes90 6.505 0.023 5.945 0.024 5.654 0.024
GJ 473 A 15.06* Tor99 13.25* Tor99 7.69* Tor99 7.06* Tor99 6.59* Tor99
GJ 473 B 15.11* Tor99 13.24* Tor99 7.82* Tor99 7.26* Tor99 7.03* Tor99
GJ 551 14.36 Leg92 12.88 Bes90 11.05 Bes90 9.43 Bes90 7.43 Bes90 5.357 0.023 4.835 0.057 4.384 0.033
GJ 559 A 0.64 Bes90 0.01 Bes90 0.35 Bes90 0.68 Bes90
GJ 559 B 2.18 Bes90 1.34 Bes90 0.87 Bes90 0.46 Bes90
GJ 628 12.82 Wei93 11.68 Bes90 10.10 Bes90 8.94 Bes90 7.42 Bes90 5.950 0.024 5.373 0.040 5.075 0.024
GJ 674 10.90 Bes90 9.37 Bes90 8.30 Bes90 6.97 Bes90 5.711 0.019 5.154 0.033 4.855 0.018
GJ 687 11.76 Leg92 10.64 Wei96 9.17 Wei96 8.08 Wei96 6.68 Wei96 5.335 0.021 4.766 0.033 4.548 0.021
GJ 699 12.54 Leg92 11.31 Bes90 9.57 Bes90 8.35 Bes90 6.79 Bes90 5.244 0.020 4.834 0.034 4.524 0.020
GJ 725 A 11.55 Leg92 10.42 Wei96 8.90 Wei96 7.83 Wei96 6.48 Wei96 5.189 0.017 4.741 0.036 4.432 0.020
GJ 725 B 12.41 Leg92 11.28 Wei96 9.69 Wei96 8.57 Wei96 7.13 Wei96 5.721 0.020 5.197 0.024 5.000 0.022
SCR 1845-6357 AB 17.39 Hen06 14.99 Hen06 12.46 Hen06 9.544 0.023 8.967 0.027 8.508 0.020 joint
GJ 729 12.18 Bes90 10.44 Bes90 9.21 Bes90 7.65 Bes90 6.222 0.018 5.655 0.034 5.370 0.016
GJ 1245 A 15.31 Leg92 13.46* Hen99 11.81 Wei96 9.78 Wei96 8.09* Hen93 7.53* Hen93 7.21* Hen93 joint BRI
GJ 1245 C 16.75* Hen99 9.35* Hen93 8.61* Hen93 8.24* Hen93
GJ 1245 B 15.98 Leg92 14.01 Wei96 12.36 Wei96 10.27 Wei96 8.275 0.025 7.728 0.031 7.387 0.018
GJ 820 A 8.63 Joh66 7.40 Joh66 6.03 Joh66 4.86 Joh66 4.03 Joh66 3.114 0.268 2.540 0.198 2.248 0.318
GJ 820 B 8.62 Leg92 7.40 Leg92 6.03 Leg92 4.41 Leg92 3.546 0.278 2.895 0.218 2.544 0.328
GJ 825 9.29 Le192 8.09 Bes90 6.67 Bes90 5.77 Bes90 4.91 Bes90 3.915 Mou76 3.270 Mou76 3.075 Mou76
GJ 832 11.36 Leg92 10.18 Bes90 8.66 Bes90 7.66 Bes90 6.47 Bes90 5.349 0.032 4.766 0.256 4.501 0.018
GJ 845 A 6.74 Joh66 5.73 Bes90 4.68 Bes90 4.06 Bes90 3.53 Bes90 2.894 0.292 2.349 0.214 2.237 0.240
GJ 845 BC 11.010 0.020 11.306 0.024 11.208 0.024 joint
GJ 860 A 9.86* Hen93 5.91* Hen93 5.33* Hen93 5.02* Hen93
GJ 860 B 11.41* Hen93 7.10* Hen93 6.47* Hen93 6.39* Hen93
GJ 866 AC 15.83 Leg92 14.33 Bes90 12.94* Hen99 10.70 Bes90 8.64 Bes90 7.06* Lei90 6.46* Lei90 6.05* Lei90 joint UBRI
GJ 866 B 13.34* Hen99 7.62* Lei90 7.02* Lei90 6.61* Lei90
GJ 876 12.90 Wei93 11.76 Bes90 10.18 Bes90 9.00 Bes90 7.43 Bes90 5.934 0.019 5.349 0.049 5.010 0.021
GJ 887 8.84 Bes90 7.34 Bes90 6.37 Bes90 5.32 Bes90 4.338 0.258 3.608 0.230 3.465 0.200
GJ 905 15.65 Leg92 14.20 Wei96 12.29 Wei96 10.77 Wei96 8.82 Wei96 6.884 0.025 6.247 0.027 5.929 0.020
GJ 166 A 4.43 Bes90 3.96 Bes90 3.54 Bes90 3.013 0.238 2.594 0.198 2.498 0.236
GJ 166 B 8.88 Kid91 9.56 Kid91 9.53 Kid91 9.849 0.029 9.986 0.039 9.861 0.071
GJ 166 C 12.84 Rei04 11.17 Rei04 6.747 0.020 6.278 0.040 5.962 0.026

Note. – JHK & err from 2MASS unless otherwise noted.
* deconvolved using flux ratios from references given and available optical and infrared photometry
“joint” indicates unresolved photometry.
Alo95 Alonso et al. (1995)
Bes90 Bessell (1990)
Bes91 Bessell (1991)
Cos06 Costa et al. (2006)
Dea07 Deacon & Hambly (2007)
Gla75 Glass (1975)
Hen93 Henry & McCarthy (1993)
Hen99 Henry et al. (1999)
Hen06 Henry et al. (2006)
Jao05 Jao et al. (2005)
Joh66 Johnson et al. (1966)
Kid91 Kidder et al. (1991)
Lan92 Landolt (1992)
Leg92 Leggett (1992)
Lei90 Leinert et al. (1990)
Mou76 Mould & Hyland (1976)
Sub09 Subasavage et al. (2009)
Wei93 Weis (1993)
Wei96 Weis (1996)
Tor99 Torres et al. (1999)

Table 2: Five Parsec Sample: Photometry
Name LHS RA 2000.0 DEC err of SpType Ref
GJ 17 5 00 20 04.2 64 52 29 .11647 .00016 2 F9.5V Gra06
GJ 19 6 00 25 45.1 77 15 15 .13407 .00011 2 G0.0V Gra06
GJ 33 121 00 48 23.0 05 16 50 .13426 .00049 2 K2.5V Gra06
GJ 34 A 123 00 49 06.3 57 48 55 .16823 .00046 2 G3.0V Mon01
GJ 53 A 8 01 08 16.4 54 55 13 .13267 .00074 2 G5.0V Joh53
GJ 66 A 01 39 47.6 56 11 47 .12999 .00208 2 K5.0V Mon01
GJ 66 B 01 39 47.6 56 11 36 .12999 .00208 2 K5.0V Mon01
GJ 68 1287 01 42 29.8 20 16 07 .13275 .00049 2 K1.0V Gra06
GJ 105 A 15 02 36 04.9 06 53 13 .13906 .00044 2 K3.0V Gra06
GJ 139 19 03 19 55.7 43 04 11 .16547 .00019 2 G8.0V Pas94
GJ 150 1581 03 43 14.9 09 45 48 .11063 .00022 2 K1.0III-IV Gra06
GJ 178 04 49 50.4 06 57 41 .12393 .00017 2 F6.0V Mon01
GJ 183 200 05 00 49.0 05 45 13 .11477 .00048 2 K3.0V CNS91
GJ 216 A 05 44 27.8 22 26 54 .11204 .00018 2 F6.0V Mon01
GJ 216 B 05 44 26.5 22 25 19 .11204 .00018 2 K2.0V CNS91
GJ 222 A 05 54 23.0 20 16 34 .11522 .00025 3 G0.0V CNS91
GJ 250 A 1875 06 52 18.1 05 10 25 .11465 .00043 2 K3.0V CNS91
GJ 423 A 2390 11 18 10.9 31 31 45 .11951 .00079 2 G0.0V Bat89
GJ 423 B 2391 11 18 11.0 31 31 46 .11951 .00079 2 G5.0V Bat89
GJ 432 A 308 11 34 29.5 32 49 53 .10461 .00037 2 K0.0V CNS91
GJ 434 11 41 03.0 34 12 06 .10416 .00026 2 G8.0V CNS91
GJ 442 A 311 11 46 31.1 40 30 01 .10844 .00022 2 G2.0V Gra06
GJ 451 44 11 52 58.8 37 43 07 .11013 .00040 2 G8.0V Joh53
GJ 475 2579 12 33 44.5 41 21 27 .11848 .00020 2 G0.0V CNS91
GJ 502 348 13 11 52.4 27 52 41 .10952 .00017 2 G0.0V CNS91
GJ 506 349 13 18 24.3 18 18 40 .11690 .00022 2 G7.0V Gra06
GJ 566 A 14 51 23.4 19 06 02 .14757 .00072 2 G8.0V Ruc95
GJ 566 B 14 51 23.4 19 06 02 .14757 .00072 2 K4.0V Mon99
GJ 570 A 387 14 57 28.0 21 24 56 .17062 .00067 3 K4.0V Gra06
GJ 631 3224 16 36 21.4 02 19 29 .10249 .00040 2 K2.0V Mon01
GJ 638 16 45 06.4 33 30 33 .10195 .00070 2 K7.0V CNS91
GJ 663 A 437 17 15 20.9 26 36 09 .16812 .00040 4 K1.0V CNS91
GJ 663 B 438 17 15 21.0 26 36 10 .16812 .00040 4 K1.0V CNS91
GJ 664(C)* 439 17 16 13.4 26 32 46 .16812 .00040 4 K5.0V CNS91
GJ 667 A 442 17 18 57.2 34 59 23 .13822 .00070 2 K3.0V CNS91
GJ 667 B 443 17 19 01.9 34 59 33 .13822 .00070 2 K5.0V CNS91
GJ 666 A 444 17 19 03.8 46 38 10 .11371 .00069 2 G8.0V CNS91
GJ 673 447 17 25 45.2 02 06 41 .12987 .00071 2 K7.0V CNS91
GJ 695 A 3326 17 46 27.5 27 43 14 .12032 .00016 2 G5.0IV CNS91
GJ 702 A 458 18 05 27.4 02 29 59 .19596 .00087 2 K0.0V CNS91
GJ 702 B 459 18 05 27.4 02 29 56 .19596 .00087 2 K5.0V CNS91
GJ 713 A 3379 18 21 03.4 72 43 58 .12343 .00044 3 F7.0V CNS91
GJ 713 B 18 21 03.4 72 43 58 .12343 .00044 3 G8.0V Far10
GJ 721 18 36 56.3 38 47 01 .12985 .00032 3 A0.0V CNS91
GJ 764 447 19 32 21.6 69 39 40 .17379 .00018 2 K0.0V CNS91
GJ 768 3490 19 50 47.0 08 52 06 .19540 .00046 3 A7.0V CNS91
GJ 780 485 20 08 43.6 66 10 55 .16371 .00017 2 G8.0IV Gra06
GJ 783 A 486 20 11 11.9 36 06 04 .16626 .00027 2 K2.5V Gra06
GJ 785 488 20 15 17.4 27 01 59 .11222 .00030 2 K2.0V Gra06
GJ 827 3674 21 26 26.6 65 21 58 .10797 .00019 2 F9.0V Gra06
GJ 881(A) 22 57 39.0 29 37 20 .13042 .00037 4 A4.0V Gra06
GJ 879(B)* 22 56 24.1 31 33 56 .13042 .00037 4 K5.0V CNS91
GJ 884 3885 23 00 16.1 22 31 28 .12175 .00069 2 K7.0V Gra06
GJ 892 71 23 13 17.0 57 10 06 .15284 .00028 2 K3.0V CNS91

Note. – * Designates component to above system with different GJ number.
Bat89 Batten et al. (1989)
CNS91 Catalog of Nearby Stars, Gliese & Jahreiss (1991)
Far10 Farrington et al. (2010)
Gra06 Gray et al. (2006)
Mon99 Montes et al. (1999)
Mon01 Montes et al.(2001)
Pas94 Pasquini et al. (1994)
Ruc95 Ruck & Smith (1995)
Joh53 Johnson & Morgan (1953)

Table 3: Extended Ten Parsec Sample
Name U Uref B Bref V Vref R Rref I Iref J err H err K err Notes
GJ 17 4.82 Joh66 4.80 Bes90 4.22 Bes90 3.89 Bes90 3.57 Bes90 3.17 Gla75 2.87 Gla75 2.78 Gla75
GJ 19 3.53 Joh66 3.42 Bes90 2.80 Bes90 2.45 Bes90 2.12 Bes90 1.72 Gla75 1.40 Gla75 1.32 Gla75
GJ 33 6.60 Bes90 5.72 Bes90 5.21 Bes90 4.76 Bes90 4.24 Joh68 3.72 Joh68 3.48 Joh68
GJ 34 A 4.04 Joh66 4.02 Joh66 3.44 Joh66 3.1 USNOB 2.8 USNOB 2.109 0.570 2.086 0.504 1.988
GJ 53 AB 5.96 Joh66 5.87 Joh66 5.18 Joh66 4.7 USNOB 4.4 USNOB 3.86 Joh68 3.39 Joh68 3.36 Joh68 joint
GJ 66 A 6.69 Hog00 5.80 Hog00 4.043 0.378 3.510 0.282
GJ 66 B 6.84 Mer86 5.96 Mer86 3.573 3.558 0.270
GJ 68 6.57 Joh66 6.08 Joh66 5.24 Joh66 4.7 USNOB 4.3 USNOB 3.855 0.24 3.391 0.226 3.285 0.266
GJ 105 AC 6.78 Bes90 5.81 Bes90 5.24 Bes90 4.74 Bes90 4.07 Gla75 3.52 Gla75 3.45 Gla75 joint
GJ 139 5.19 Joh66 4.97 Bes90 4.26 Bes90 3.85 Bes90 3.47 Bes90 2.95 Gla75 2.59 Gla75 2.52 Gla75
GJ 150 4.45 Bes90 3.53 Bes90 3.03 Bes90 2.59 Bes90 1.99 Gla75 1.53 Gla75 1.45 Gla75
GJ 178 3.64 Joh66 3.65 Bes90 3.19 Bes90 2.92 Bes90 2.67 Bes90 2.35 Gla75 2.15 Gla75 2.07 Gla75
GJ 183 7.29 Bes90 6.23 Bes90 5.44 Bes90 4.69 Bes90 4.389 0.244 3.797 0.214 3.706 0.228
GJ 216 A 4.07 Joh66 4.06 Bes90 3.59 Bes90 3.30 Bes90 3.02 Bes90 2.804 0.276 2.606 0.236 2.508 0.228
GJ 216 B 7.12 Bes90 6.18 Bes90 5.63 Bes90 5.17 Bes90 4.845 0.198 4.158 0.202 4.131 0.264
GJ 222 AB 5.04 Joh66 5.00 Joh66 4.41 Joh66 4.0 USNOB 3.8 USNOB 3.34 Joh68 3.04 Joh68 2.97 Joh68 joint
GJ 250 A 7.64 Bes90 6.59 Bes90 5.98 Bes90 5.45 Bes90 5.013 0.252 4.294 0.258 4.107 0.036
GJ 423 AC 4.78 Lep05 4.27 Lep05 3.9 USNOB 3.7 USNOB 2.462 0.294 2.231 0.204 2.142 0.230 joint
GJ 423 BD 5.36 Lep05 4.74 Lep05 4.4 USNOB 4.0 USNOB joint
GJ 432 A 6.78 Bes90 5.97 Bes90 5.52 Bes90 5.10 Bes90 4.784 0.228 4.138 0.214 4.022 0.036
GJ 434 6.28 Joh66 6.05 Bes90 5.33 Bes90 4.9 USNOB 4.5 USNOB 3.99 Joh68 3.61 Joh68 3.60 Joh68
GJ 442 A 5.56 Bes90 4.90 Bes90 4.5 USNOB 4.2 USNOB 3.931 0.276 3.490 0.238 3.489 0.278
GJ 451 7.37 Joh66 7.20 Joh66 6.45 Joh66 6.0 USNOB 5.6 USNOB 4.89 Gla75 4.43 Gla75 4.37 Gla75
GJ 475 4.91 Joh66 4.86 Joh66 4.27 Joh66 3.9 USNOB 3.6 USNOB 3.23 Joh66 2.905 0.198 2.84 Joh66
GJ 502 4.92 Joh66 4.84 Joh66 4.26 Joh66 3.9 USNOB 3.6 USNOB 3.24 Gla75 2.90 Gla75 2.87 Gla75
GJ 506 5.69 Joh66 5.43 Bes90 4.72 Bes90 4.33 Bes90 3.97 Bes90 3.334 0.200 2.974 0.176 2.956 0.236
GJ 566 A 5.68 Lut71 5.44 Lut71 4.72 Lut71 4.52 Bre64 4.24 Bre64 2.660 0.448 2.253 0.698 1.971 0.600 joint JHK
GJ 566 B 9.29 Lut71 8.14 Lut71 6.97 Lut71 6.30 Bre64 5.86 Bre64
GJ 570 A 7.88 Joh66 6.82 Joh66 5.71 Joh66 3.663 0.258 3.085 0.196 3.048 0.224
GJ 631 6.57 Bes90 5.76 Bes90 5.31 Bes90 4.9 Bes90 4.33 Joh66 4.053 0.208 3.87 Joh66
GJ 638 9.48 Joh53 8.11 Joh65 7.3 USNOB 6.6 USNOB 5.48 0.023 4.878 0.018 4.712 0.021
GJ 663 AB 5.93 Tor06 5.08 Tor06 joint
GJ 664(C)* 7.48 Bes90 6.32 Bes90 5.62 Bes90 5.04 Bes90 4.155 0.25 3.466 0.256
GJ 667 AB 7.77 Joh66 6.95 Joh66 5.91 Joh66 4.97 Joh66 4.38 Joh66 3.903 0.262 3.230 0.206 3.123 0.278 joint
GJ 666 A 6.35 Bes90 5.47 Bes90 5.00 Bes90 4.54 Bes90 4.077 0.996 3.146 0.664 3.421 0.282
GJ 673 8.89 Bes90 7.53 Bes90 6.69 Bes90 5.94 Bes90 4.934 0.024 4.341 0.044 4.14 Gla75
GJ 695 AD 4.56 Joh66 4.17 Joh66 3.42 Joh66 2.9 USNOB 2.6 USNOB 2.13 Joh66 1.559 0.184 1.77 Joh66 joint
GJ 702 A 5.31 Egg65 4.98 Egg65 4.20 Egg65 3.87 Bre64 3.61 Bre64 2.343 0.296 1.876 0.244 1.791 0.304 joint JHK
GJ 702 B 7.15 Egg65 6.00 Egg65 5.26 Bre64 4.82 Bre64
GJ 713 AB 4.01 Joh66 4.07 Joh66 3.58 Joh66 3.3 USNOB 3.0 USNOB 2.588 0.260 2.372 0.188 2.216 0.252 joint
GJ 721 0.02 Joh66 0.02 Bes90 0.03 Bes90 0.04 Bes90 0.04 Bes90 0.02 Joh66 0.029 0.146 0.02 Joh66
GJ 764 5.86 Oja84 5.46 Oja93 4.68 Oja93 4.2 USNOB 3.8 USNOB 3.32 Joh66 3.039 0.214 2.78 Joh66
GJ 768 1.07 Joh66 0.99 Bes90 0.77 Bes90 0.64 Bes90 0.50 Bes90 0.39 Joh66 0.102 0.220 0.26 Joh66
GJ 780 4.76 Joh66 4.31 Bes90 3.55 Bes90 3.14 Bes90 2.79 Bes90 2.35 Gla75 2.03 Gla75 1.93 Gla75
GJ 783 A 6.19 Joh66 5.32 Joh66 3.518 0.300 2.999 0.422 3.008 0.602
GJ 785 6.61 Bes90 5.73 Bes90 5.23 Bes90 4.81 Bes90 4.112 0.294 3.582 0.266 3.501 0.232
GJ 827 4.58 Joh66 4.71 Bes90 4.22 Bes90 3.92 Bes90 3.61 Bes90 3.27 Gla75 3.00 Gla75 2.90 Gla75
GJ 881(A) 1.30 Joh66 1.24 Bes90 1.15 Bes90 1.10 Bes90 1.07 Bes90 1.02 Gla75 1.03 Gla75 0.99 Gla75
GJ 879(B)* 7.56 Bes90 6.46 Bes90 5.8 Bes90 5.78 Bes90 4.533 0.037 3.804 0.210 3.805 0.240
GJ 884 9.25 Bes90 7.86 Bes90 7.00 Bes90 6.23 Bes90 5.346 0.021 4.696 0.076 4.478 0.016
GJ 892 7.46 Oja84 6.56 Oja93 5.57 Oja93 4.9 USNOB 4.5 USNOB 3.80 Gla75 3.27 Gla75 3.18 Gla75

Note. – * Designates component to above system with different GJ number.
JHK & err from 2MASS unless otherwise noted.
“joint” indicates unresolved photometry.
Bes90 Bessell (1990)
Bre64 Breckinridge & Kron (1964)
Egg65 Eggen (1965)
Gla75 Glass (1975)
Hog00 Høg et al. (2000)
Joh53 Johnson & Morgan (1953)
Joh66 Johnson et al. (1966)
Joh68 Johnson et al. (1968)
Lep05 Lépine & Shara (2005)
Lut71 Lutz (1971)
Mer86 Mermilliod (1986)
Oja84 Oja (1984)
Oja93 Oja (1993)
Tor06 Torres et al. (2006)
USNOB Monet et al. (2003)
.

Table 4: Extended Ten Parsec Sample: Photometry
Filter Zero Point (Å) Ref
U 4.18e-9 3660 Bessell et al.(1998)
B 6.32e-9 4380 Bessell et al.(1998)
V 3.63e-9 5450 Bessell et al.(1998)
R 2.18e-9 6410 Bessell et al.(1998)
I 1.13e-9 7980 Bessell et al.(1998)
J 3.14e-10 12350 Cohen et al.(2003)
H 1.11e-10 16620 Cohen et al.(2003)
K 4.29e-11 21590 Cohen et al.(2003)

Note. – Zero points have units of ergs cm sec Å.

Table 5: Zero Points
Star SpType - Model ModelFixR Published Ref.
GJ 244 A A1.0V 0.040 10000 9600 9900200 1.645 1.711 0.013 Kervella et al (2003a)
GJ 280 A F5.0IV-V 1.028 6700 6500 6524 1.898 2.048 0.025 Kervella et al (2003b)
GJ 559 A G2.0V 1.490 6000 5700 581050 1.103 1.224 0.003 Kervella et al (2003b)
GJ 71 G8.5V 1.696 5700 5400 5264100 0.708 0.816 0.013 Di Folco et al.(2004)
GJ 631 K2.0V 1.890 5500 5300 533741 0.710 0.759 0.012 Boyajian et al.(2012)
GJ 166 A K0.5V 1.932 5200 5100 514314 0.735 0.806 0.004 Boyajian et al.(2012)
GJ 559 B K0.0V 1.940 5400 5100 526050 0.775 0.863 0.005 Kervella et al (2003b)
GJ 144 K2.0V 1.954 5200 5000 5135100 0.689 0.743 0.005 Di Folco et al.(2004)
GJ 33 K2.5V 2.240 5200 5000 495014 0.643 0.695 0.004 Boyajian et al.(2012)
GJ 105 A K3.0V 2.360 5000 4700 466217 0.677 0.795 0.006 Boyajian et al.(2012)
GJ 892 K3.0V 2.390 5000 4800 469916 0.698 0.778 0.005 Boyajian et al.(2012)
GJ 702 A K0.0V 2.409 5500 5700 540752 0.754 0.831 0.004 Boyajian et al.(2012)
GJ 845 A K5.0V 2.443 4900 4600 546859 0.608 0.732 0.007 Demory et al.(2009)
GJ 570 A K4.0V 2.662 4700 4700 450758 0.734 0.739 0.019 Boyajian et al.(2012)
GJ 820 B K7.0V 3.486 4300 4200 404080 0.530 0.595 0.008 Kervella et al (2008)
GJ 380 K7.0V 3.628 4200 4200 408115 0.599 0.642 0.005 Boyajian et al.(2012)
GJ 820 A K5.0V 3.782 4000 4100 4400100 0.709 0.665 0.005 Kervella et al (2008)
GJ 702 B* K5.0V 4393149 0.670 0.009 Boyajian et al.(2012)
GJ 191 M2.0VI 3.801 3800 3600 3570156 0.249 0.291 0.025 Ségransan et al.(2003)
GJ 887 M2.0V 3.875 3800 3700 379745 0.414 0.459 0.011 Demory et al.(2009)
GJ 411 M2.0V 3.969 3700 3500 346517 0.338 0.392 0.004 Boyajian et al.(2012)
GJ 412 A M1.0V 4.001 3700 3600 349739 0.353 0.398 0.009 Boyajian et al.(2012)
GJ 15 A M1.5V 4.062 3800 3700 373049 0.323 0.379 0.006 Berger et al. (2006)
GJ 725 A M3.0V 4.468 3400 3400 340715 0.344 0.356 0.004 Boyajian et al.(2012)
GJ 687 M3.0V 4.622 3400 3200 341328 0.406 0.418 0.007 Boyajian et al.(2012)
GJ 725 B M3.5V 4.690 3300 3200 310428 0.275 0.323 0.006 Boyajian et al.(2012)
GJ 699 M4.0V 5.046 3100 3100 322410 0.198 0.187 0.001 Boyajian et al.(2012)
GJ 551 M5.0V 6.666 2700 2900 309856 0.167 0.141 0.007 Demory et al.(2009)

Note. – Model refers to temperatures from our model, while, ModelFixR refers to temperatures derived while holding the radius to values obtained through long baseline interferometry.
* GJ 702B does not have enough resolved photometry for a model solution.

Table 6: Comparison of Derived Temperatures and Radii for Nearby Stars Using Our SED Fits and Interferometric Results
Model Model FixR
Name SpType R EHZ Inner R EHZ Outer R EHZ Lin R EHZ Inner R EHZ Outer R EHZ Lin
() (K) (AU) (AU) (AU) () (K) (AU) (AU) (AU)
Sun G2.0V 0.917 6000 0.789 1.686 0.897 1.00 5800 0.804 1.718 0.914
DEN 1048-3956 M8.5V 0.134 2000 0.013 0.027 0.014
GJ 1 M1.5V 0.349 3700 0.114 0.244 0.130
GJ 15 A M1.5V 0.323 3800 0.112 0.239 0.127 0.387 3700 0.127 0.271 0.144
GJ 15 B M3.5V 0.197 3200 0.048 0.103 0.055
GJ 54.1 M4.5V 0.181 2900 0.036 0.078 0.042
GJ 65 A M5.5V 0.248 2600 0.040 0.086 0.046
GJ 65 B M6.0V 0.225 2700 0.039 0.084 0.045
GJ 71 G8.0V 0.700 5700 0.545 1.164 0.619 0.816 5400 0.570 1.218 0.648
GJ 83.1 M4.5V 0.195 2900 0.039 0.084 0.045
GJ 144 K2.0V 0.630 5400 0.440 0.940 0.500 0.735 5000 0.440 0.941 0.500
GJ 166 A K0.5V 0.735 5200 0.476 1.017 0.541 0.806 5000 0.483 1.031 0.549
GJ 166 C M4.5V 0.249 3200 0.061 0.130 0.069
GJ 191 M1.5VI 0.240 3800 0.083 0.177 0.094 0.291 3500 0.085 0.182 0.097
GJ 234 A M4.0V 0.287 3000 0.062 0.132 0.070
GJ 234 B M5.5V 0.155 2700 0.027 0.058 0.031
GJ 244 A* A1.0V 1.645 10000 3.942 8.420 4.478 1.711 9600 3.779 8.071 4.293
GJ 273 M3.5V 0.316 3200 0.077 0.165 0.088
GJ 280 A* F5.0IV-V 1.906 6700 2.050 4.380 2.329 2.048 6500 2.073 4.429 2.356
GJ 380 K7.0V 0.648 4100 0.261 0.558 0.297 0.642 4100 0.259 0.552 0.294
GJ 388 M3.0V 0.452 3300 0.118 0.251 0.133
GJ 406 M6.0V 0.162 2500 0.024 0.052 0.028
GJ 411 M2.0V 0.338 3700 0.111 0.237 0.126 0.392 3500 0.115 0.246 0.130
GJ 412 A M1.0V 0.353 3700 0.116 0.247 0.131 0.398 3600 0.124 0.264 0.140
GJ 412 B M5.5V 0.152 2600 0.025 0.053 0.028
GJ 447 M4.0V 0.213 3000 0.046 0.098 0.052
GJ 473 A M5.0V 0.212 2700 0.037 0.079 0.042
GJ 473 B M7.0V 0.177 2900 0.036 0.076 0.040
GJ 551 M5.5V 0.167 2700 0.029 0.062 0.033 0.141 2900 0.028 0.061 0.032
GJ 559 A G2.0V 0.884 6700 0.951 2.031 1.080 1.224 5700 0.953 2.036 1.083
GJ 559 B K0.0V 0.774 5400 0.541 1.155 0.614 0.863 5200 0.559 1.194 0.635
GJ 628 M3.0V 0.321 3200 0.079 0.168 0.089
GJ 674 M2.5V 0.355 3400 0.098 0.210 0.112
GJ 687 M3.0V 0.406 3400 0.112 0.240 0.128 0.418 3400 0.116 0.247 0.132
GJ 699 M4.0V 0.198 3100 0.046 0.097 0.051 0.187 3100 0.043 0.092 0.048
GJ 725 A M3.0V 0.344 3400 0.095 0.204 0.109 0.356 3400 0.099 0.211 0.112
GJ 725 B M3.5V 0.275 3300 0.072 0.153 0.081 0.323 3200 0.079 0.169 0.090
GJ 729 M3.5V 0.214 3100 0.049 0.105 0.056
GJ 820 A K5.0V 0.709 4000 0.272 0.581 0.309 0.665 4100 0.268 0.572 0.304
GJ 820 B K7.0V 0.530 4300 0.235 0.502 0.267 0.595 4200 0.252 0.537 0.286
GJ 825 M0.0V 0.516 4100 0.208 0.444 0.236
GJ 832 M1.5V 0.423 3600 0.131 0.280 0.149
GJ 845 A K5.0V 0.608 4900 0.350 0.747 0.397 0.732 4600 0.371 0.793 0.422
GJ 860 A M3.0V 0.328 3300 0.085 0.183 0.098
GJ 860 B M4.0V 0.194 3200 0.048 0.102 0.054
GJ 866 B MV 0.215 2700 0.037 0.080 0.043
GJ 876 A M4.0V 0.390 3100 0.090 0.191 0.101
GJ 887 M1.5V 0.414 3800 0.143 0.306 0.163 0.491 3700 0.161 0.344 0.183
GJ 905 M5.5V 0.216 2700 0.038 0.080 0.042
GJ 1002 M5.0V 0.142 2900 0.029 0.061 0.032
GJ 1061 M5.0V 0.178 2700 0.031 0.066 0.035
GJ 1111 M6.0V 0.162 2400 0.022 0.048 0.026
GJ 1245 A M5.5V 0.194 2700 0.034 0.072 0.038
GJ 1245 B M6.0V 0.150 2700 0.026 0.056 0.030
GJ 1245 C M7.0V 0.171 2100 0.018 0.039 0.021
LHS 288 M5.5V 0.150 2700 0.026 0.056 0.030
LHS 292 M6.5V 0.146 2400 0.020 0.043 0.023
LP 944-020 M9.0V 0.091 2000 0.009 0.019 0.010
SCR 1845-6357 A M8.5V 0.129 2000 0.012 0.026 0.014
SO 02531652 M7.0V 0.156 2400 0.022 0.046 0.024

Note. – This table shows model radius, temperature, inner and outer HZ radius, and the HZ width in AU in columns 3-7. Columns 8-12 show radius, temperature, inner and outer HZ radius, and the HZ width in AU based on the method of holding the stellar radius to the values obtained through long baseline interferometry (see Table 6). * Sirius (GJ 244A) and Procyon (GJ 280A) are included as benchmarks, but are not used in final EHZ calculations because of companion white dwarfs.

Table 7: Empirical Habitable Zones (EHZs) for the Five Parsec Sample
Model Model FixR
Name SpType R EHZ Inner R EHZ Outer R EHZ Lin R EHZ Inner R EHZ Outer R EHZ Lin
() (K) (AU) (AU) (AU) () (K) (AU) (AU) (AU)
GJ 17 F9.5V 0.989 6100 0.882 1.884 1.002
GJ 19 G0.0V 1.709 6000 1.474 3.149 1.675
GJ 33 K2.5V 0.643 5200 0.417 0.890 0.473 0.695 5000 0.416 0.889 0.473
GJ 34 A G3.0V 0.989 6100 0.882 1.884 1.002
GJ 66 A K5.0V 0.740 5100 0.461 0.985 0.524
GJ 66 B K5.0V 0.794 4900 0.457 0.976 0.519
GJ 68 K1.0V 0.739 5400 0.516 1.103 0.587
GJ 105 A K3.0V 0.677 5000 0.406 0.866 0.460 0.795 4700 0.421 0.899 0.478
GJ 139 G8.0V 0.812 5700 0.632 1.350 0.718
GJ 178 F6.0V 1.244 6600 1.299 2.774 1.475
GJ 183 K3.0V 0.791 4800 0.437 0.933 0.496
GJ 216 A F6.0V 1.137 6600 1.187 2.534 1.347
GJ 216 B K2.0V 0.593 5300 0.399 0.853 0.454
GJ 250 A K3.0V 0.597 4900 0.344 0.734 0.390
GJ 432 A K0.0V 0.627 5500 0.455 0.971 0.516
GJ 434 G8.0V 0.793 5700 0.617 1.319 0.702
GJ 442 A G2.0V 0.792 6000 0.683 1.459 0.776
GJ 451 G8.0V 0.542 5400 0.378 0.807 0.429
GJ 475 G0.0V 0.952 6100 0.849 1.813 0.964
GJ 502 G0.0V 1.029 6100 0.918 1.960 1.042
GJ 506 G7.0V 0.927 5700 0.722 1.542 0.820
GJ 566 A G8.0V 0.534 6200 0.491 1.049 0.558
GJ 566 B K4.0V 0.376 5000 0.225 0.481 0.256
GJ 570 A K4.0V 0.734 4700 0.389 0.830 0.441 0.739 4700 0.391 0.836 0.444
GJ 631 K2.0V 0.710 5500 0.515 1.099 0.584 0.759 5300 0.511 1.091 0.580
GJ 638 K7.0V 0.620 4100 0.250 0.534 0.284
GJ 663 A K1.0V 0.523 1.118 0.595
GJ 663 B K1.0V 0.523 1.118 0.595
GJ 664 (C)* K5.0V 0.581 4600 0.295 0.629 0.334
GJ 666 A G8.0V 0.841 5200 0.545 1.164 0.619
GJ 667 A K3.0V 0.399 0.853 0.454
GJ 667 B K5.0V 0.285 0.607 0.322
GJ 673 K7.0V 0.644 4100 0.259 0.554 0.295
GJ 702 A K0.0V 0.754 5500 0.547 1.168 0.621 0.670 5700 0.522 1.114 0.593
GJ 702 B K5.0V 0.411 5100 0.256 0.735 0.479
GJ 721 A0.0V 2.543 9800 5.852 12.50 6.648
GJ 764 K0.0V 0.694 5500 0.503 1.075 0.572
GJ 768 A7.0V 1.701 7800 2.480 5.297 2.817
GJ 783 A K2.5V 0.751 5000 0.450 0.961 0.511
GJ 785 K2.0V 0.802 5100 0.450 1.068 0.618
GJ 827 F9.0V 0.970 6400 0.952 2.034 1.082
GJ 879 (B)* K5.0V 0.592 4700 0.313 0.669 0.356
GJ 881 (A) A4.0V 1.635 9200 3.316 7.084 3.768
GJ 884 K7.0V 0.553 4200 0.234 0.499 0.265
GJ 892 K3.0V 0.698 5000 0.418 0.893 0.475 0.778 4800 0.430 0.918 0.488

Note. – * Designates wide component to above system with different GJ number.
This table shows model radius, temperature, inner and outer HZ radius, and the HZ width in AU in columns 3-7 for the extended 10 pc sample.
HZs for GJ 663A, GJ 663B, GJ 667A, and GJ 667B are estimated using the - relationship (see Section 5.2).

Table 8: Empirical Habitable Zones (EHZs) for the Extended Ten Parsec Sample
Star Sep a e i() () () P(yr) T Ref
GJ 15 AB 40 Eggen (1996)
GJ 34 AB 1199 0.497 34.76 98.43 88.59 480 1889.6 Strand (1969)
GJ 53 AB 101 0.561 106.8 47.3 152.7 21.75 1975.74 Drummond et al. (1995)
GJ 65 AB 206 0.615 127.3 150.5 285.4 26.52 1971.88 Worley & Behall (1973)
GJ 66 AB 782 0.534 142.8 13.1 18.37 483.66 1813.5 van Albada (1957)
GJ 105 AC-B 165 Golimowski et al. (2000)
GJ 105 AC 33 Golimowski et al. (2000)
GJ 166 A-BC 83 Baize & Petit (1989)
GJ 166 BC 694 0.410 108.9 150.9 327.8 252.1 1849.6 Heintz (1974)
GJ 216 AB 95 Eggen (1956)
GJ 222 AB 0688 0.451 95.94 126.36 111.57 14.11 1999.9 Han & Gatewood (2002)
GJ 234 AB 104 0.371 51.8 30.7 223 16.12 1999.38 Ségransan et al. (2000)
GJ 244 AB 756 0.592 136.5 55.57 147.27 50.09 1894.13 Gatewood & Gatewood (1978)
GJ 250 AB 58 Eggen (1956)
GJ 280 AB 4496 0.365 31.9 284.8 88.8 40.38 1967.86 Irwin et al. (1992)
GJ 412 AB 28 Gould (2003)
GJ 423 AC-BD 2533 0.421 112.1 101.3 127.3 59.84 1995.05 Heintz (1996)
GJ 423 AC 0056 0.53 94.9 263.5 143.0 1.832 1986.50 Mason et al. (1995)
GJ 423 BD *274,000km 0.015 Mason et al. (1995)
GJ 432 AB 17 Henry et al. (2002)
GJ 442 AB 254 Poveda et al. (1994)
GJ 473 AB 0926 0.295 103.00 143.48 347.2 15.64 1992.30 Torres et al. (1999)
GJ 559 AB 1757 0.518 79.2 204.85 231.65 79.91 1875.66 Pourbaix et al. (2002)
GJ 551-GJ 559 AB 218 Poveda et al. (1994)
GJ 566 AB 494 0.51 139 347 203 151.6 1909.3 Söderhjelm (1999)
GJ 570 A-BC 3234 0.20 72.53 317.31 252.1 2130 1689 Hale (1994)
GJ 570 BC 0151 0.756 107.6 195.9 127.56 0.846 1996.51 Forveille et al. (1999)
GJ 570 ABC-D 2583 Burgasser et al. (2000)
GJ 663 AB 130 0.916 99.79 -85.8 -90.2 470.9 1677.9 Irwin et al. (1996)
GJ 663 AB-GJ 664 742 Luyten (1957)
GJ 666 AB 1042 0.779 35.64 131.78 333.44 693.24 1907.2 Wieth-Knudsen (1957)
GJ 667 AB 181 0.58 128 313 247 42.15 1975.9 Söderhjelm (1999)
GJ 695 AD 143 0.32 68.0 81.8 92 65 1951.0 Turner et al. (2001); Heintz (1994)
GJ 695 AD-BC 34 Raghavan et al. (2010)
GJ 695 BC 136 0.178 66.2 60.7 174.0 43.2 1965.4 Couteau (1959)
GJ 702 AB 455 0.499 121.16 302.12 14.0 88.38 1895.94 Pourbaix (2000)
GJ 713 AB 0124 0.428 74.42 230.30 119.3 0.768 1984.83 Farrington et al. (2010)
GJ 725 AB 1388 0.53 66.0 136.9 234.6 408 1775.0 Heintz (1987)
GJ 783 AB 71 Poveda et al. (1994)
GJ 820 AB 2443 0.414 52.7 173.4 153.17 691.61 1689.14 Baize (1950)
GJ 845 A-BC 4023 Scholz et al. (2003)
GJ 845 BC 0732 McCaughrean et al. (2004)
GJ 860 AB 2383 0.410 167.2 154.5 211.0 44.67 1970.22 Heintz (1986)
GJ 866 AC 001 0.000 117 1991.71 Delfosse et al. (1999)
GJ 866 AC-B 0346 0.446 112 161.5 337.6 2.25 1997.53 Delfosse et al. (1999)
GJ 881-GJ 879 197 Poveda et al. (1994)
GJ 1245 AC-B 7969 0.320 135.0 80.0 38.0 15.22 1983.1 Tokovinin (1997)
GJ 1245 AC 0800 Tokovinin (1997)
SCR 1845-6357 AB 1170 Biller et al. (2006)

Note. – *asin(i)

Table 9: Orbital Properties of Multiple Systems
5 pc Sample Total 10 pc Sample
SpType # of stars EHZ AU # of stars EHZ AU
A 0(1) 3 (4) 13.2
F 0(1) 4 (6) 4.9
G 3 2.6 14 (21) 11.9
K 7 2.9 34 (35) 15.4
M 48(50) 3.3 384*(400)* 26.1*

Note. – The numbers used in the table reflect the number of stars in each sample for which the EHZ was calculated (and include the Sun). Photometrically unresolved binaries, evolved stars, and substellar objects for which EHZs were not calculated are excluded from these totals. *The totals for the M type population to 10 pc are a factor of eight greater than the population within 5 pc, estimated via scaling by the volume (). Numbers in parentheses are totals including photometrically unresolved binaries and evolved stars.

Table 10: Total EHZ by Spectral Type.
Star Planet Semimajor Axis e Ref HZinner HZouter
(AU) (AU) (AU)
GJ 139 b 0.12070.0020 0.0 Pepe et al. (2011) 0.632 1.350
GJ 139 c 0.20360.0034 0.0 Pepe et al. (2011) 0.632 1.350
GJ 139 d 0.34990.0059 0.0 Pepe et al. (2011) 0.632 1.350
GJ 144 b 3.390.36 0.7020.039 Benedict et al. (2006) 0.439 0.938
GJ 176 b 0.066 0 Forveille et al. (2009) 0.136 0.290
GJ 442 A b 0.460.04 0.340.14 Tinney et al. (2011) 0.689 1.472
GJ 506 b 0.055.0e-6 0.120.11 Vogt et al. (2010a) 0.689 1.472
GJ 506 c 0.21750.0001 0.140.06 Vogt et al. (2010a) 0.719 1.537
GJ 506 d 0.4760.001 0.350.09 Vogt et al. (2010a) 0.719 1.537
GJ 559 B b* 0.041850.0003 0 Dumusque et al. (2012) 0.541 1.155
GJ 581 b 0.04 0 Mayor et al. (2009) 0.083 0.179
GJ 581 c 0.07 0.170.07 Mayor et al. (2009) 0.083 0.179
GJ 581 d 0.22 0.380.09 Mayor et al. (2009) 0.083 0.179
GJ 581 e 0.03 0 Mayor et al. (2009) 0.083 0.179
GJ 581 f* 0.7580.015 Vogt et al. (2010b) 0.083 0.179
GJ 581 g* 0.14601.4e-4 Vogt et al. (2010b) 0.083 0.179
GJ 667 C b 0.049 0.1720.043 Anglada-Escudé et al. (2012) 0.096 0.205
GJ 667 C c 0.1230.020 0.27 Anglada-Escudé et al. (2012) 0.096 0.205
GJ 674 b 0.039 0.200.02 Bonfils et al. (2007) 0.098 0.210
GJ 785 b 0.3100.005 0.300.09 Howard et al. (2010) 0.500 1.068
GJ 832 b 3.40.4 0.120.11 Bailey et al. (2009) 0.131 0.280
GJ 849 b 2.35 0.060.09 Butler et al. (2006) 0.136 0.290
GJ 876 b 0.20832.0e-5 0.02921.5e-3 Rivera et al. (2010) 0.090 0.191
GJ 876 c 0.12962.6e-5 0.25498.0e-4 Rivera et al. (2010) 0.090 0.191
GJ 876 d 0.02081.5e-7 0.2070.055 Rivera et al. (2010) 0.090 0.191
GJ 876 e 0.34430.0013 0.0550.012 Rivera et al. (2010) 0.090 0.191
GJ 881 b 115 0.11 Kalas et al. (2008) 3.316 7.084

Note. – Bold rows indicate the planet is in the EHZ for at least part of its orbit. * Planet detection controversial.

Table 11: Exoplanets within Ten Parsecs
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