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== Gliese 667 C ==
== Gliese 667 C ==
Gliese 667 C is the smallest star in the system, with only around 33%<ref name="Pineda2021"/> of the mass of the Sun and 34%<ref name="Pineda2021"/> of the Sun's radius, orbiting approximately 230 AU from the Gliese 667 AB pair.<ref name="Anglada-Escudé-2013">{{cite journal |title=A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone |url=http://www.eso.org/public/archives/releases/sciencepapers/eso1328/eso1328a.pdf |date=2013-06-07 |archive-url=https://web.archive.org/web/20130630214924/http://www.eso.org/public/archives/releases/sciencepapers/eso1328/eso1328a.pdf |archive-date=2013-06-30|first1=Guillem |last1=Anglada-Escudé |first2=Mikko |last2=Tuomi |first3=Enrico |last3=Gerlach |first4=Rory |last4=Barnes |first5=René |last5=Heller |first6=James S. |last6=Jenkins |first7=Sebastian |last7=Wende |first8=Steven S. |last8=Vogt |first9=R. Paul |last9=Butler |last10= Reiners |first10=Ansgar |last11= Jones |first11=Hugh R. A. |journal=[[Astronomy & Astrophysics]] |doi=10.1051/0004-6361/201321331 |access-date=2013-06-25|arxiv = 1306.6074 |bibcode = 2013A&A...556A.126A |volume=556 |pages=A126|s2cid=14559800 }}</ref> It is a [[red dwarf]] with a stellar classification of M1.5. This star is radiating only 1.4% of the Sun's luminosity from its outer atmosphere at a relatively cool [[effective temperature]] of 3,440&nbsp;K.<ref name="Pineda2021"/> This temperature is what gives it the red-hued glow that is a characteristic of [[M-type star]]s.<ref name=csiro/> The apparent magnitude of the star is 10.25, giving it an absolute magnitude of about 11.03. It is known to have a system of two planets; claims have been made for up to five additional planets<ref name="Anglada-Escudé"/> but this is likely to be in error due to failure to account for correlated noise in the radial velocity data.<ref name="ferozhobson2014"/><ref name="RobertsonMahadevan2014"/> The red dwarf status of the star would allow planet Cc, which is in the habitable zone, to receive minimal amounts of [[ultraviolet]] radiation.<ref name="Anglada-Escudé-2013"/>


{{Merge|Gliese 667 C|target=Gliese 667|discuss=Talk:Gliese 667#Proposed merge 02 July 2014|date=July 2014}}
=== Planetary system ===
{{Starbox begin
[[Image:Gliese 667.jpg|thumb|left|Artist's impression of Gliese 667 Cb with the Gliese 667 A/B binary in the background]]
| name=[[Gliese Catalogue of Nearby Stars|Gliese]] 667 C
[[File:Gliese 667 Cc sunset.jpg|thumb|left|An artist's impression of GJ 667 Cc, a potentially habitable planet orbiting a red dwarf constituent in a trinary [[star system]]]]
}}
{{Starbox image
| image =
<div style="position: relative">[[File:Scorpius constellation map.svg|250px|alt=Diagram showing star positions and boundaries of the constellation of Scorpius and its surroundings]]
<div style="position: absolute; left: 77px; top: 154px">[[File:Cercle rouge 100%.svg|10px]]</div>
</div>
| caption = A [[star chart]] of the constellation of Scorpius showing the position of Gliese 667 (red circle at lower left)
}}
{{Starbox observe
| epoch=J2000
| constell=[[Scorpius]]
| ra={{RA|17|18|57.16483}}<ref name=aaa474_2_653/>
| dec={{DEC|−34|59|23.1416}}<ref name=aaa474_2_653/>
| appmag_v=10.20<ref name=aaa367_521/> }}
{{Starbox character
| class=M1.5V<ref name=aaa367_521/><ref name=geballe/>
| b-v=1.57
| u-b=1.17
| variable=[[flare star]]
}}
{{Starbox astrometry
| radial_v=6.5<ref name="Anglada-Escudé-2012"/>
| prop_mo_ra=1129.76<ref name=aaa474_2_653/>
| prop_mo_dec=−77.02<ref name=aaa474_2_653/>
| parallax=146.29
| p_error=9.03
| parallax_footnote=<ref name=aaa474_2_653/>
| absmag_v=11.03
}}
{{Starbox detail
| mass=0.31<ref name="Anglada-Escudé-2012"/>
| radius=0.42<ref name=aaa367_521/>
| luminosity=0.0137<ref name="Anglada-Escudé-2012"/>
| temperature={{nowrap|3,700 ± 100}}<ref name="Anglada-Escudé-2012"/>
| metal_fe={{nowrap|–0.59 ± 0.10}}<ref name="Anglada-Escudé-2012"/>
| rotation=105 days <ref name="Anglada-Escudé-2012"/>
| age_gyr=2-10<ref name="Anglada-Escudé-2012"/>
}}
{{Starbox catalog
| names= [[Luyten Half-Second catalogue|LHS]]&nbsp;443, 142&nbsp;G.&nbsp;Scorpii&nbsp;C, [[Cordoba Durchmusterung|CD]]−34°11626C, [[Gliese-Jahreiss catalogue|GJ]]&nbsp;667&nbsp;C, [[Henry Draper catalogue|HD]]&nbsp;156384&nbsp;C, [[Hipparcos catalogue|HIP]]&nbsp;84709&nbsp;C, [[Harvard Revised catalogue|HR]]&nbsp;6426&nbsp;C, [[Smithsonian Astrophysical Observatory|SAO]]&nbsp;208670&nbsp;C
}}
{{Starbox reference
| Simbad = GJ+667C<!-- GJ+667 = Gliese667 -->
| NSTED = GJ+667
| ARICNS = 01389<!--01387 = Gliese667 A--><!--01388 = Gliese 667 B-->
| EPE = GJ+667C
}}
{{starbox end}}
'''Gliese 667 C''', also known as '''GJ 667 C''', is a [[star]] in the [[Gliese 667]] triple star system. Located {{convert|6.8|pc|ly|abbr=off|lk=on}} away from the [[Solar System]] in the constellation [[Scorpius]], Gliese 667 C is a [[red dwarf]]<ref name=csiro /> with 1.4% of the luminosity of the [[Sun]] and a relatively cool [[effective temperature]] of 3,700 K at its surface.<ref name="Anglada-Escudé-2012"/> It is the smallest and least massive member<ref name=aaa367_521/><ref name=mnras389_2_925/> of the Gliese 667 system. Gliese 667 C has been found to have a system of two confirmed [[extrasolar planet]]s, all of which are sub-Neptunes or [[super-Earth]]s detected using the [[radial velocity]] method.<ref name="Anglada-Escudé-2013"/> The outer planet [[Gliese 667 Cc]] orbits within the habitable zone.<ref name="Anglada-Escudé-2013"/> Additional planets have been proposed, including two that would be located in the habitable zone. These in fact may be artifacts caused by a failure to account for the correlated noise in the data<ref name="ferozhobson2014"/>


==Stellar properties==
Two [[extrasolar planet]]s, [[Gliese 667 Cb]] (GJ 667 Cb) and [[Gliese 667 Cc|Cc]], have been confirmed orbiting Gliese 667 C by [[radial velocity]] measurements of GJ 667.<ref name="ferozhobson2014"/><ref name="RobertsonMahadevan2014"/> There were also thought to be up to five other potential additional planets;<ref name="Anglada-Escudé-2012"/><ref name="Anglada-Escudé"/> however, it was later shown that they are likely to be artifacts resulting from correlated noise.<ref name="ferozhobson2014"/><ref name="RobertsonMahadevan2014"/>
Gliese 667 C is a class M2V star that orbits at a projected separation of 230 AU from Gliese 667 AB, and is believed to be at least two billion years old.<ref name="Anglada-Escudé-2013"/>


===Activity===
Planet Cb was first announced by the [[European Southern Observatory]]'s [[HARPS]] group on 19 October 2009. The announcement was made together with 29 other planets, while Cc was first mentioned by the same group in a pre-print made public on 21 November 2011.<ref name=arxiv11115019/> Announcement of a refereed journal report came on 2 February 2012 by researchers at the [[University of Göttingen]]/[[Carnegie Institution for Science]].<ref name="Anglada-Escudé-2012"/><ref name="Göttingen"/> In this announcement, GJ 667 Cc was described as one of the [[List of potentially habitable exoplanets|best candidates]] yet found to harbor liquid water, and thus, potentially, support life on its surface.<ref name="Space-20120202"/> A detailed orbital analysis and refined orbital parameters for Gliese 667 Cc were presented.<ref name="Anglada-Escudé-2012"/> Based on GJ 667 C's bolometric luminosity, GJ 667 Cc would receive 90% of the [[Solar irradiance|light]] Earth does;<ref name=news/> however, much of that [[Electromagnetic radiation#Electromagnetic spectrum|electromagnetic radiation]] would be in the invisible infrared light part of the spectrum.
Although [[Stellar classification|M-class]] stars can remain active for much longer than the Sun, Gliese 667 C is now a relatively inactive star. This allowed investigation of its planetary system by examining small variations in its radial velocity. At the current time, it means that the planets would receive negligible levels of UV and X-ray radiation from chromospheric emission of the star and stellar flares.<ref name="Anglada-Escudé-2013" />


===Habitable zone===
From the surface of Gliese 667 Cc, the second-confirmed planet out that orbits along the middle of the habitable zone, Gliese 667 C would have an angular diameter of 1.24 degrees—2.3 times<ref name="Apparentsize" group="note"><math>\begin{smallmatrix}\frac {h} {{h}_{\odot}}={\left( \frac{{{T}_{\odot}}_{\rm eff}} {{T}_{\rm eff}} \right)^2} *\frac{\sqrt{L}} {a}\end{smallmatrix}</math>.{{citation needed|date=March 2012}}
where <math>\begin{smallmatrix}{h}\end{smallmatrix}</math> is the angular diameter of the star from the surface of the planet in orbit (GJ667Cc in this case), <math>\begin{smallmatrix}{{h}_{\odot}}\end{smallmatrix}</math> is the angular diameter of the Sun (sol) from the surface of Earth, <math>\begin{smallmatrix}{{T}_{\odot}}_{\rm eff}\end{smallmatrix}</math> is the effective temperature of the Sun (sol), <math>\begin{smallmatrix}{{T}_{\rm eff}}\end{smallmatrix}</math> the effective temperature of the star, <math>\begin{smallmatrix}{L}\end{smallmatrix}</math> is the luminosity of the star as a fraction of the Sun's luminosity and <math>\begin{smallmatrix}{a}\end{smallmatrix}</math> is the distance of the planet from the star in AU. This formula has been used as the luminosity and surface temperature published do not agree with the published radius. If you calculate the radius from the formula radius=sqrt(luminosity)/temp^2 (with all units given in multiples of the Sun's values), you will see that the luminosity and temperature give a radius of 0.286 times the radius of the Sun, not the same figure published in the literature. If you calculate the angular diameter in the sky using a trigonometric formula (atan(distance/radius)*2), the angular diameter derived using this revised radius agrees with the figures given here, by the shortcut formula above, which essentially makes the same calculation.<!--used this formula rather than the simpler h=1/d*a or angular diameter = 2arcsin*(1/2dact/D) because the diameter comes from a different source paper and is not consistent with luminosity, temperature and distance figures which all come from the same paper by Anglada-Escudé, Guillem et al., 2012-->
</ref> larger than the Sun appears from the surface of the Earth, covering 5.4 times more area—but would still only occupy 0.003% of Gliese 667 Cc's sky sphere or 0.006% of the visible sky when directly overhead.


{{Main|Circumstellar habitable zone}}
At one point, up to five additional planets were thought to exist in the system, with three of them thought to be relatively certain to exist.<ref name="Anglada-Escudé"/> However, multiple subsequent studies showed that the other proposed planets in the system were likely to be artifacts of noise and stellar activity, cutting the number of confirmed planets down to two. While one analysis did find some evidence for a third planet, Gliese 667 Cd with a period of about 90 days, but was unable to confirm it,<ref name="ferozhobson2014"/> other studies found that that specific signal very likely originates from the stellar rotation.<ref name="RobertsonMahadevan2014"/><ref name="SuárezMascareño2015"/> Thus, despite its inclusion in a list of planet candidates in a 2019 [[preprint]],<ref name="Tuomi2019"/> it is unlikely that Gliese 667 Cd exists.

The habitable zone of a star has been defined as a "Goldilocks region" of space which is neither too hot nor too cold for a planet with liquid water under an Earth-like atmosphere. The planet must be far enough away from its star to avoid a "moist greenhouse" in which water vapor retains so much heat that any ocean would boil and hydrogen would be lost to space, but close enough to avoid [[snowball Earth|global ice coverage]]. The most recently published calculations of the habitable zone, when applied to the Gliese 667 C system, predict that the habitable zone extends from an inner edge around 0.095–0.126 AU to an outer edge of 0.241–0.251 AU. A broader definition of the zone might apply if planets with small but non-negligible amounts of water were detected.<ref name="Anglada-Escudé-2013"/><ref name="abe-2011"/>

==Planetary system==
As of February 2014, the most recent orbital solution contains two planets: one with a minimum mass around 5.6 Earth masses in a 7.2-day orbit, and a second planet of at least 3.7 Earth masses in a 28-day orbit. These planets are designated [[Gliese 667 Cb]] and [[Gliese 667 Cc]] respectively.<ref name="ferozhobson2014"/> The location of the second planet puts it close to the inner edge of the system's habitable zone, though it is unknown as to whether it actually supports life.<ref name="Anglada-Escudé-2013"/>

The radial velocity data for the star also contains periodic signals at 105 days and 91 days. The first of these is close to the rotation period of the star, and the stellar activity indicators also show variations at this period. It is likely that this period is due to processes intrinsic to the star rather than an orbiting planet. The activity indicators also show variability on a 91-day period, again suggesting that this period is the result of stellar variations rather than an additional planet.<ref name="ferozhobson2014"/>


{{OrbitboxPlanet begin
{{OrbitboxPlanet begin
| name = Gliese 667 C
| name = Gliese 667 C
| table_ref = <ref name="RobertsonMahadevan2014"/>
| table_ref =
| period_unit = day
| period_unit = day
}}
}}
{{OrbitboxPlanet
{{OrbitboxPlanet
| exoplanet = [[Gliese 667 Cb|b]]
| exoplanet = [[Gliese 667 Cb|b]]
| mass_earth = {{val|5.6|0.3|p=≥}}
| mass_earth = ≥5.661&nbsp;±&nbsp;0.437
| semimajor = {{val|0.050431|0.000004|fmt=none}}
| semimajor = 0.050&nbsp;±&nbsp;0.002
| period = {{val|7.1999|0.0009|fmt=none}}
| period = 7.200&nbsp;±&nbsp;0.001
| eccentricity = {{val|0.15|0.05}}
| eccentricity = 0.122&nbsp;±&nbsp;0.078
}}
}}
{{OrbitboxPlanet
{{OrbitboxPlanet
| exoplanet = [[Gliese 667 Cc|c]]
| exoplanet = [[Gliese 667 Cc|c]]
| mass_earth = {{val|4.1|0.6|p=≥}}
| mass_earth = ≥3.709&nbsp;±&nbsp;0.682
| semimajor = {{val|0.12501|0.00009|fmt=none}}
| semimajor = 0.125&nbsp;±&nbsp;0.004
| period = {{val|28.10|0.03}}
| period = 28.143&nbsp;±&nbsp;0.029
| eccentricity = {{val|0.27|0.1}}
| eccentricity = 0.133&nbsp;±&nbsp;0.098
}}
}}
{{Orbitbox end}}
{{Orbitbox end}}

{{Clear}}
===Gliese 667 Cb===
{{main|Gliese 667 Cb}}
'''Gliese 667 Cb''' was the first planet to be detected orbiting Gliese 667 C, and is the more massive of the two known planets. It was first announced in an ESO press release in 2009.<ref name="ESO-2009"/> Modelling the expected tidal forces experienced by this planet suggest that if it is terrestrial in nature, tidal heating would keep the planet completely molten.<ref name="MakarovBerghea2014"/>

===Gliese 667 Cc===
[[File:Gliese 667 Cc sunset.jpg|thumb|left|An artist's impression of GJ 667 Cc, a potentially habitable planet orbiting a red dwarf star in a [[star system|triple star system]].]]
{{main|Gliese 667 Cc}}
'''Gliese 667 Cc''' was first mentioned in a pre-print made public on 21 November 2011, claiming that a discovery paper from the same group was in preparation (the paper was finally published in a refereed journal in 2013).<ref name="Bonfils2013"/> However, the announcement of a refereed journal report came on 2 February 2012 by researchers at the [[Carnegie Institution for Science]] and the [[University of Göttingen]].<ref name="Anglada-Escudé-2012"/><ref name="Göttingen"/> In that announcement, Gliese 667 Cc was described as one of the [[List of potential habitable exoplanets|best candidates]] yet found to harbor liquid water, and thus, potentially, support life on its surface.<ref name="Space-20120202"/> A detailed orbital analysis and refined orbital parameters for Gliese 667 Cc were also presented at the time.<ref name="Anglada-Escudé-2012"/>

Based on GJ 667 C's [[bolometric luminosity]], GJ 667 Cc would receive 90% of the [[solar flux|light]] Earth does;<ref name=news/> however much of that [[Electromagnetic radiation#Electromagnetic spectrum|electromagnetic radiation]] would be in the invisible [[infrared]]. Based on [[blackbody]] temperature calculations, GJ 667 Cc should absorb more overall electromagnetic radiation and thereby have an [[equilibrium temperature]] of 277.4 [[kelvin|K]], as compared with 254.3 K for the Earth.<ref name="Anglada-Escudé-2012"/> If it is terrestrial in nature, the planet is expected to experience strong tidal heating that may lead to high levels of geological activity on the planet.<ref name="MakarovBerghea2014"/>

===History of discovery===
Gliese 667 Cb, the first planet of the system to be reported, was first announced by the [[European Southern Observatory]]'s [[High Accuracy Radial Velocity Planet Searcher|HARPS]] group on 19 October 2009, together with 29 other planets.<ref name="ESO-2009"/> The orbital parameters were subsequently given in a paper that appeared on the arXiv pre-print server in 2011, together with the parameters for the second planet Gliese 667 Cc.<ref name="Bonfils2013"/> The paper was eventually published in 2013. In the meantime, a second study of the system

Preliminary radial-velocity measurements indicated the presence of an additional super-Earth candidate (Gliese 667 Cd), orbiting in an "extended habitable zone" where large quantities of CO<sub>2</sub> and other greenhouse gases may make life possible (a planet similar to [[Gliese 581 d]]).<ref name="Space-20120202" /> However, this candidate was less certain at the time due to similarities of the period to rather clear signals detected in several activity indices. Its phase sampling was also sparse, causing severe aliasing and potential confusion. Another likely period for this same candidate was proposed to be 91 days.<ref name="Anglada-Escudé-2012" /> An additional, long-period signal was found in the data. While the trend is largely consistent with the star's orbit around the A/B primary, a minor curvature in the trend suggests that the object may have a shorter period. A preliminary solution of 7100 days was derived which consistent with a roughly [[Saturn]]-mass planet. Not enough data was available to decide conclusively the nature of such long-period trend.<ref name="Anglada-Escudé-2012" />

In December 2012, a new solution was obtained using HARPS data only. Such solution contained 6 [[Doppler effect|Doppler]] signals that were tentatively associated to 5 to 6 planet candidates.<ref name=Gregory/> The 7.2 and 28.1 days signals correspond to the periods of two previously known planets around the star.
Among the other signals, one was suspected to be generated by stellar activity and another one was proposed at a period of 30 days, too close to 28.1 days (period of the securely detected GJ 667Cc) to be in a stable orbit. In an informal interview, Guillem Anglada-Escudé, of the original discovery team, noted that the corresponding system of planets was unstable, and that the possibility of astrophysical false-positives had not been properly done to distinguish between activity induced and genuine Keplerian signals.<ref name="IO9"/> The claim appeared as a submitted article (not yet accepted by June 2013) and the proposed solution lacked of several basic checks. Therefore, the claim was considered preliminary but suggestive.

On 25 June 2013 a new orbital solution was announced by the initial discovery team, with five strongly-detected planet candidates and two less certain objects. Of the five candidates, three including the previously-detected planet Gliese 667Cc would be located in the habitable zone of the star. The additional habitable zone planet candidates were proposed to have orbital periods of 39 and 62 days. The orbital solution retained the 90-day planet candidate orbiting beyond the outer edge of the habitable zone. With the new planets, Gliese 667C would be the star with most known low-mass planets in its habitable zone.<ref name=kramer-2013 /> The five first signals also match the five stronger signals reported by Phil Gregory in his preliminary solution proposed in December 2012<ref name=Gregory/> and listed in the six-planet solution section. The two additional candidates are less certain and rely on the assumption of dynamical stability of the system.<ref name="Anglada-Escudé-2013"/>

Further investigation of the data indicated significant levels of correlated noise. Using the erroneous assumption of white noise, the researchers could detect up to five planets. Using a model that accounted for correlated noise only two planets could be detected, together with long period signals attributed to stellar activity. The current model of the system therefore only includes two planets.<ref name="ferozhobson2014"/>


==References==
==References==
<!--- See http://en.wikipedia.org/wiki/Wikipedia:Footnotes on how to create references using <ref></ref> tags which will then appear here automatically -->
{{Reflist|30em|refs=
{{reflist|3|refs=

<ref name=news>{{cite web| url=http://www.mn.uio.no/astro/english/research/news-and-events/news/astronews-2012-02-17.html | title=Life on Gliese 667Cc? | publisher =Institute of Theoretical Astrophysics | author=Sven Wedemeyer-Böhm }}</ref>

<ref name=aaa474_2_653>{{citation | last1=van Leeuwen | first1=F. | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 |date=November 2007 | pages=653–664 | doi=10.1051/0004-6361:20078357 | bibcode=2007A&A...474..653V | arxiv=0708.1752 }}</ref>

<ref name=Gregory>{{cite journal | arxiv=1212.4058 | title= Additional Keplerian Signals in the HARPS data for Gliese 667C from a Bayesian Re-analysis | author=Philip C. Gregory|bibcode = 2012arXiv1212.4058G }}</ref>

<ref name=aaa367_521>{{citation | display-authors=1 | last1=Pasinetti Fracassini | first1=L. E. | last2=Pastori | first2=L. | last3=Covino | first3=S. | last4=Pozzi | first4=A. | title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics | journal=Astronomy and Astrophysics | volume=367 | pages=521–524 |date=February 2001 | doi=10.1051/0004-6361:20000451 | bibcode=2001A&A...367..521P |arxiv = astro-ph/0012289 }} ''Note:'' see VizieR catalogue [http://cdsarc.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/521 J/A+A/367/521].</ref>

<ref name="abe-2011">{{cite doi|10.1089/ast.2010.0545}}</ref>

<ref name="Bonfils2013">{{cite journal|title=The HARPS search for southern extra-solar planets. XXXI. The M-dwarf sample|author=Bonfils, X.; Delfosse, X.; Udry, S.; Forveille, T.; Mayor, M.; Perrier, C.; Bouchy, F.; Gillon, M.; Lovis, C.; Pepe, F.; Queloz, D.; Santos, N. C.; Ségransan, D.; Bertaux, J.-L.|year=2013|journal=Astronomy & Astrophysics|volume=549|at=id.A109|doi=10.1051/0004-6361/201014704|bibcode=2013A&A...549A.109B|arxiv=1111.5019}}</ref>

<ref name="Anglada-Escudé-2012">{{cite journal|title=A Planetary System around the nearby M Dwarf GJ 667C with At Least One Super-Earth in Its Habitable Zone|author=Anglada-Escudé, Guillem; Arriagada, Pamela; Vogt, Steven S.; Rivera, Eugenio J.; Butler, R. Paul; Crane, Jeffrey D.; Shectman, Stephen A.; Thompson, Ian B.; Minniti, Dante; Haghighipour, Nader; Carter, Brad D.; Tinney, C. G.; Wittenmyer, Robert A.; Bailey, Jeremy A.; O'Toole, Simon J.; Jones, Hugh R. A.; Jenkins, James S.|year=2012|journal=The Astrophysical Journal Letters|volume=751|issue=1|at=article id. L16|doi=10.1088/2041-8205/751/1/L16|bibcode=2012ApJ...751L..16A|arxiv=1202.0446}}</ref>

<ref name="Anglada-Escudé-2013">{{cite journal |title=A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone |url=http://www.eso.org/public/archives/releases/sciencepapers/eso1328/eso1328a.pdf |date=2013-06-07 |archiveurl=http://web.archive.org/web/20130630214924/http://www.eso.org/public/archives/releases/sciencepapers/eso1328/eso1328a.pdf |archivedate=2013-06-30|first1=Guillem |last1=Anglada-Escudé |first2=Mikko |last2=Tuomi |first3=Enrico |last3=Gerlach |first4=Rory |last4=Barnes |first5=René |last5=Heller |first6=James S. |last6=Jenkins |first7=Sebastian |last7=Wende |first8=Steven S. |last8=Vogt |first9=R. Paul |last9=Butler |last10= Reiners |first10=Ansgar |last11= Jones |first11=Hugh R. A. |journal=[[Astronomy & Astrophysics]] |doi=10.1051/0004-6361/201321331 |accessdate=2013-06-25|arxiv = 1306.6074 |bibcode = 2013A&A...556A.126A }}</ref>

<ref name=csiro>{{citation | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | accessdate=2012-01-16 |archiveurl=http://web.archive.org/web/20121014150117/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archivedate=2012-10-14}}</ref>

<ref name="ESO-2009">{{cite press release|url=http://www.eso.org/public/news/eso0939/|title=32 New Exoplanets Found|authors=<!-- staff writer(s); no by-line -->|agency=ESO|date=2009-10-19|accessdate=2014-08-29}}</ref>

<ref name="ferozhobson2014">{{cite journal|title=Bayesian analysis of radial velocity data of GJ667C with correlated noise: evidence for only two planets|author=Feroz, F.; Hobson, M. P.|year=2014|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=437|issue=4|pages=3540–3549|arxiv=1307.6984|bibcode=2014MNRAS.437.3540F}}</ref>

<ref name=geballe>{{citation | title=Toward spectral classification of L and T dwarfs: infrared and optical spectroscopy and analysis | date=January 2002 | work=The Astrophysical Journal | publisher=The American Astronomical Society | url=http://iopscience.iop.org/0004-637X/564/1/466/pdf/0004-637X_564_1_466.pdf | accessdate=2012-02-14 }}</ref>

<ref name="Göttingen">University of Göttingen. ''Presseinformation: Wissenschaftler entdecken möglicherweise bewohnbare Super-Erde - Göttinger Astrophysiker untersucht Planeten in 22 Lichtjahren Entfernung.'' Nr. 17/2012 - 02.02.2012. [http://www.uni-goettingen.de/de/3240.html?cid=4110 Announcement on university homepage, retrieved 2012-02-02]</ref>

<ref name="IO9">{{cite web|url=http://io9.com/5969407/astronomer-discovers-three-potentially-habitable-planets-orbiting-around-one-red-dwarf|title=Astronomer discovers three potentially habitable planets orbiting around one red dwarf|date=18 December 2012|accessdate=21 March 2013|publisher=io9|author=Dvorsky, George|archiveurl=http://web.archive.org/web/20130703065540/http://io9.com/5969407/astronomer-discovers-three-potentially-habitable-planets-orbiting-around-one-red-dwarf |archivedate=2013-07-03}}</ref>

<ref name=kramer-2013>{{cite news | url=http://www.space.com/21706-habitable-alien-planets-gliese-667c.html | title=Found! 3 Super-Earth Planets That Could Support Alien Life | work=Space.com | date=25 June 2013 | agency=TechMediaNetwork | accessdate=2013-06-26 | author=Kramer, Miriam |archiveurl=http://web.archive.org/web/20130629232449/http://www.space.com/21706-habitable-alien-planets-gliese-667c.html |archivedate=2013-06-29}}</ref>

<ref name="MakarovBerghea2014">{{cite journal|title=Dynamical Evolution and Spin-orbit Resonances of Potentially Habitable Exoplanets. The Case of GJ 667C|author=Makarov, Valeri V.; Berghea, Ciprian|journal=The Astrophysical Journal|year=2014|volume=780|issue=2|at=article id. 124|doi=10.1088/0004-637X/780/2/124|bibcode=2014ApJ...780..124M|arxiv=1311.4831}}</ref>

<ref name=mnras389_2_925>{{citation | last1=Tokovinin | first1=A. | title=Comparative statistics and origin of triple and quadruple stars | journal=Monthly Notices of the Royal Astronomical Society | volume=389 | issue=2 | pages=925–938 |date=September 2008 | doi=10.1111/j.1365-2966.2008.13613.x | bibcode=2008MNRAS.389..925T |arxiv = 0806.3263 }}</ref>

<ref name="Space-20120202">{{cite web |last=Chow |first=Denise |title=Newfound Alien Planet is Best Candidate Yet to Support Life, Scientists Say|url=http://www.space.com/14444-alien-planet-super-earth-habitable-zone.html |date=February 2, 2012 |publisher=[[Space.com]] |accessdate= February 3, 2012 | archiveurl=http://web.archive.org/web/20130419165746/http://www.space.com/14444-alien-planet-super-earth-habitable-zone.html |archivedate=2013-04-19}}</ref>


<ref name="GaiaDR3">{{Cite Gaia DR3|5975663354131618304}}</ref>
<ref name="GaiaDR3">{{Cite Gaia DR3|5975663354131618304}}</ref>

Revision as of 07:18, 14 September 2023

Gliese 667 A/B/C
Diagram showing star positions and boundaries of the constellation of Scorpius and its surroundings
A star chart of the constellation of Scorpius showing the position of Gliese 667
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 17h 18m 57.16483s[1]
Declination −34° 59′ 23.1416″[1]
Apparent magnitude (V) 5.91/7.20/10.20[2]
Characteristics
Spectral type K3V + K5V + M1.5V[2][3]
U−B color index 0.83/???/1.17
B−V color index 1.03/???/1.57
Variable type A: suspected
B: unknown
C: flare star[citation needed]
Astrometry
Radial velocity (Rv)6.13±0.30[4] km/s
Proper motion (μ) RA: 1131.517 mas/yr[4]
Dec.: −215.569 mas/yr[4]
Parallax (π)138.0663 ± 0.0283 mas[4]
Distance23.623 ± 0.005 ly
(7.243 ± 0.001 pc)
Absolute magnitude (MV)7.07/8.02/11.03
Details
GJ 667 AB
Mass0.73 / 0.69[5] M☉
Radius0.76 / 0.70[2] R☉
Metallicity [Fe/H]–0.59[6] dex
GJ 667 C
Mass0.327±0.008[7] M☉
Radius0.337±0.014[7] R☉
Luminosity0.01439±0.00035[7] L☉
Temperature3,443+75
−71[7] K
Metallicity [Fe/H]–0.59 ± 0.10[8] dex
Rotation105 days [8]
Age2–10[8] Gyr
Orbit[9]
CompanionGliese 667 B
Period (P)42.15 yr
Semi-major axis (a)1.81″
Eccentricity (e)0.58
Inclination (i)128°
Longitude of the node (Ω)313°
Periastron epoch (T)1975.9
Argument of periastron (ω)
(secondary)		247°
Other designations
142 G. Scorpii, CD−34°11626, GJ 667, HD 156384, HIP 84709, HR 6426, LHS 442/442/443, SAO 208670, 2MASS J17185698-3459236
Database references
SIMBADThe system
AB
A
B
C
Cb
Cc
Ce
Cf
Exoplanet ArchiveGliese 667 C
ARICNSGliese 667 A
B
C

Gliese 667 (142 G. Scorpii) is a triple-star system in the constellation Scorpius lying at a distance of about 7.2 parsecs (23 light-years) from Earth. All three of the stars have masses smaller than the Sun. There is a 12th-magnitude star close to the other three, but it is not gravitationally bound to the system. To the naked eye, the system appears to be a single faint star of magnitude 5.89.

The system has a relatively high proper motion, exceeding 1 second of arc per year.

The two brightest stars in this system, GJ 667 A and GJ 667 B, are orbiting each other at an average angular separation of 1.81 arcseconds with a high eccentricity of 0.58. At the estimated distance of this system, this is equivalent to a physical separation of about 12.6 AU, or nearly 13 times the separation of the Earth from the Sun. Their eccentric orbit brings the pair as close as about 5 AU to each other, or as distant as 20 AU, corresponding to an eccentricity of 0.6.[note 1][10] This orbit takes approximately 42.15 years to complete and the orbital plane is inclined at an angle of 128° to the line of sight from the Earth. The third star, GJ 667 C, orbits the GJ 667 AB pair at an angular separation of about 30", which equates to a minimum separation of 230 AU.[8][11] GJ 667 C also has a system of two confirmed super-Earths and a number of additional doubtful candidates, though the innermost, GJ 667 Cb, may be a gas dwarf; GJ 667 Cc, and the controversial Cf and Ce, are in the circumstellar habitable zone.[12]

Gliese 667 AB

The largest star in the system, Gliese 667 A (GJ 667 A), is a K-type main-sequence star of stellar classification K3V.[2] It has about 73%[5] of the mass of the Sun and 76%[2] of the Sun's radius, but is radiating only around 12-13% of the luminosity of the Sun.[13] The concentration of elements other than hydrogen and helium, what astronomers term the star's metallicity, is much lower than in the Sun with a relative abundance of around 26% solar.[6] The apparent visual magnitude of this star is 6.29, which, at the star's estimated distance, gives an absolute magnitude of around 7.07 (assuming negligible extinction from interstellar matter).

Like the primary, the secondary star Gliese 667 B (GJ 667 B) is a K-type main-sequence star, although it has a slightly later stellar classification of K5V. This star has a mass of about 69%[5] of the Sun, or 95% of the primary's mass, and it is radiating about 5% of the Sun's visual luminosity. The secondary's apparent magnitude is 7.24, giving it an absolute magnitude of around 8.02.

Gliese 667 C

Gliese 667 C
Diagram showing star positions and boundaries of the constellation of Scorpius and its surroundings
A star chart of the constellation of Scorpius showing the position of Gliese 667 (red circle at lower left)
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 17h 18m 57.16483s[1]
Declination −34° 59′ 23.1416″[1]
Apparent magnitude (V) 10.20[2]
Characteristics
Spectral type M1.5V[2][14]
U−B color index 1.17
B−V color index 1.57
Variable type flare star
Astrometry
Radial velocity (Rv)6.5[8] km/s
Proper motion (μ) RA: 1129.76[1] mas/yr
Dec.: −77.02[1] mas/yr
Parallax (π)146.29 ± 9.03 mas[1]
Distance22 ± 1 ly
(6.8 ± 0.4 pc)
Absolute magnitude (MV)11.03
Details
Mass0.31[8] M☉
Radius0.42[2] R☉
Luminosity0.0137[8] L☉
Temperature3,700 ± 100[8] K
Metallicity [Fe/H]–0.59 ± 0.10[8] dex
Rotation105 days [8]
Age2-10[8] Gyr
Other designations
LHS 443, 142 G. Scorpii C, CD−34°11626C, GJ 667 C, HD 156384 C, HIP 84709 C, HR 6426 C, SAO 208670 C
Database references
SIMBADdata
Exoplanet Archivedata
ARICNSdata

Gliese 667 C, also known as GJ 667 C, is a star in the Gliese 667 triple star system. Located 6.8 parsecs (22 light-years) away from the Solar System in the constellation Scorpius, Gliese 667 C is a red dwarf[15] with 1.4% of the luminosity of the Sun and a relatively cool effective temperature of 3,700 K at its surface.[8] It is the smallest and least massive member[2][5] of the Gliese 667 system. Gliese 667 C has been found to have a system of two confirmed extrasolar planets, all of which are sub-Neptunes or super-Earths detected using the radial velocity method.[16] The outer planet Gliese 667 Cc orbits within the habitable zone.[16] Additional planets have been proposed, including two that would be located in the habitable zone. These in fact may be artifacts caused by a failure to account for the correlated noise in the data[17]

Stellar properties

Gliese 667 C is a class M2V star that orbits at a projected separation of 230 AU from Gliese 667 AB, and is believed to be at least two billion years old.[16]

Activity

Although M-class stars can remain active for much longer than the Sun, Gliese 667 C is now a relatively inactive star. This allowed investigation of its planetary system by examining small variations in its radial velocity. At the current time, it means that the planets would receive negligible levels of UV and X-ray radiation from chromospheric emission of the star and stellar flares.[16]

Habitable zone

Main article: Circumstellar habitable zone

The habitable zone of a star has been defined as a "Goldilocks region" of space which is neither too hot nor too cold for a planet with liquid water under an Earth-like atmosphere. The planet must be far enough away from its star to avoid a "moist greenhouse" in which water vapor retains so much heat that any ocean would boil and hydrogen would be lost to space, but close enough to avoid global ice coverage. The most recently published calculations of the habitable zone, when applied to the Gliese 667 C system, predict that the habitable zone extends from an inner edge around 0.095–0.126 AU to an outer edge of 0.241–0.251 AU. A broader definition of the zone might apply if planets with small but non-negligible amounts of water were detected.[16][18]

Planetary system

As of February 2014, the most recent orbital solution contains two planets: one with a minimum mass around 5.6 Earth masses in a 7.2-day orbit, and a second planet of at least 3.7 Earth masses in a 28-day orbit. These planets are designated Gliese 667 Cb and Gliese 667 Cc respectively.[17] The location of the second planet puts it close to the inner edge of the system's habitable zone, though it is unknown as to whether it actually supports life.[16]

The radial velocity data for the star also contains periodic signals at 105 days and 91 days. The first of these is close to the rotation period of the star, and the stellar activity indicators also show variations at this period. It is likely that this period is due to processes intrinsic to the star rather than an orbiting planet. The activity indicators also show variability on a 91-day period, again suggesting that this period is the result of stellar variations rather than an additional planet.[17]

The Gliese 667 C planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥5.661 ± 0.437 M🜨 0.050 ± 0.002 7.200 ± 0.001 0.122 ± 0.078 — —
c ≥3.709 ± 0.682 M🜨 0.125 ± 0.004 28.143 ± 0.029 0.133 ± 0.098 — —

Gliese 667 Cb

Main article: Gliese 667 Cb

Gliese 667 Cb was the first planet to be detected orbiting Gliese 667 C, and is the more massive of the two known planets. It was first announced in an ESO press release in 2009.[19] Modelling the expected tidal forces experienced by this planet suggest that if it is terrestrial in nature, tidal heating would keep the planet completely molten.[20]

Gliese 667 Cc

An artist's impression of GJ 667 Cc, a potentially habitable planet orbiting a red dwarf star in a triple star system.
Main article: Gliese 667 Cc

Gliese 667 Cc was first mentioned in a pre-print made public on 21 November 2011, claiming that a discovery paper from the same group was in preparation (the paper was finally published in a refereed journal in 2013).[21] However, the announcement of a refereed journal report came on 2 February 2012 by researchers at the Carnegie Institution for Science and the University of Göttingen.[8][22] In that announcement, Gliese 667 Cc was described as one of the best candidates yet found to harbor liquid water, and thus, potentially, support life on its surface.[23] A detailed orbital analysis and refined orbital parameters for Gliese 667 Cc were also presented at the time.[8]

Based on GJ 667 C's bolometric luminosity, GJ 667 Cc would receive 90% of the light Earth does;[13] however much of that electromagnetic radiation would be in the invisible infrared. Based on blackbody temperature calculations, GJ 667 Cc should absorb more overall electromagnetic radiation and thereby have an equilibrium temperature of 277.4 K, as compared with 254.3 K for the Earth.[8] If it is terrestrial in nature, the planet is expected to experience strong tidal heating that may lead to high levels of geological activity on the planet.[20]

History of discovery

Gliese 667 Cb, the first planet of the system to be reported, was first announced by the European Southern Observatory's HARPS group on 19 October 2009, together with 29 other planets.[19] The orbital parameters were subsequently given in a paper that appeared on the arXiv pre-print server in 2011, together with the parameters for the second planet Gliese 667 Cc.[21] The paper was eventually published in 2013. In the meantime, a second study of the system

Preliminary radial-velocity measurements indicated the presence of an additional super-Earth candidate (Gliese 667 Cd), orbiting in an "extended habitable zone" where large quantities of CO2 and other greenhouse gases may make life possible (a planet similar to Gliese 581 d).[23] However, this candidate was less certain at the time due to similarities of the period to rather clear signals detected in several activity indices. Its phase sampling was also sparse, causing severe aliasing and potential confusion. Another likely period for this same candidate was proposed to be 91 days.[8] An additional, long-period signal was found in the data. While the trend is largely consistent with the star's orbit around the A/B primary, a minor curvature in the trend suggests that the object may have a shorter period. A preliminary solution of 7100 days was derived which consistent with a roughly Saturn-mass planet. Not enough data was available to decide conclusively the nature of such long-period trend.[8]

In December 2012, a new solution was obtained using HARPS data only. Such solution contained 6 Doppler signals that were tentatively associated to 5 to 6 planet candidates.[11] The 7.2 and 28.1 days signals correspond to the periods of two previously known planets around the star. Among the other signals, one was suspected to be generated by stellar activity and another one was proposed at a period of 30 days, too close to 28.1 days (period of the securely detected GJ 667Cc) to be in a stable orbit. In an informal interview, Guillem Anglada-Escudé, of the original discovery team, noted that the corresponding system of planets was unstable, and that the possibility of astrophysical false-positives had not been properly done to distinguish between activity induced and genuine Keplerian signals.[24] The claim appeared as a submitted article (not yet accepted by June 2013) and the proposed solution lacked of several basic checks. Therefore, the claim was considered preliminary but suggestive.

On 25 June 2013 a new orbital solution was announced by the initial discovery team, with five strongly-detected planet candidates and two less certain objects. Of the five candidates, three including the previously-detected planet Gliese 667Cc would be located in the habitable zone of the star. The additional habitable zone planet candidates were proposed to have orbital periods of 39 and 62 days. The orbital solution retained the 90-day planet candidate orbiting beyond the outer edge of the habitable zone. With the new planets, Gliese 667C would be the star with most known low-mass planets in its habitable zone.[25] The five first signals also match the five stronger signals reported by Phil Gregory in his preliminary solution proposed in December 2012[11] and listed in the six-planet solution section. The two additional candidates are less certain and rely on the assumption of dynamical stability of the system.[16]

Further investigation of the data indicated significant levels of correlated noise. Using the erroneous assumption of white noise, the researchers could detect up to five planets. Using a model that accounted for correlated noise only two planets could be detected, together with long period signals attributed to stellar activity. The current model of the system therefore only includes two planets.[17]

References

  1. ^ a b c d e f g van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 Cite error: The named reference "aaa474_2_653" was defined multiple times with different content (see the help page).
  2. ^ a b c d e f g h i Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451 Note: see VizieR catalogue J/A+A/367/521. Cite error: The named reference "aaa367_521" was defined multiple times with different content (see the help page).
  3. ^ Suárez Mascareño, A.; et al. (September 2015), "Rotation periods of late-type dwarf stars from time series high-resolution spectroscopy of chromospheric indicators", Monthly Notices of the Royal Astronomical Society, 452 (3): 2745–2756, arXiv:1506.08039, Bibcode:2015MNRAS.452.2745S, doi:10.1093/mnras/stv1441, S2CID 119181646.{{citation}}: CS1 maint: unflagged free DOI (link)
  4. ^ a b c Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  5. ^ a b c d Tokovinin, A. (September 2008), "Comparative statistics and origin of triple and quadruple stars", Monthly Notices of the Royal Astronomical Society, 389 (2): 925–938, arXiv:0806.3263, Bibcode:2008MNRAS.389..925T, doi:10.1111/j.1365-2966.2008.13613.x{{citation}}: CS1 maint: unflagged free DOI (link) Cite error: The named reference "mnras389_2_925" was defined multiple times with different content (see the help page).
  6. ^ a b Cayrel de Strobel, G.; Soubiran, C.; Ralite, N. (July 2001), "Catalogue of [Fe/H] determinations for FGK stars: 2001 edition", Astronomy and Astrophysics, 373: 159–163, arXiv:astro-ph/0106438, Bibcode:2001A&A...373..159C, doi:10.1051/0004-6361:20010525, S2CID 17519049
  7. ^ a b c d Pineda, J. Sebastian; Youngblood, Allison; France, Kevin (September 2021). "The M-dwarf Ultraviolet Spectroscopic Sample. I. Determining Stellar Parameters for Field Stars". The Astrophysical Journal. 918 (1): 23. arXiv:2106.07656. Bibcode:2021ApJ...918...40P. doi:10.3847/1538-4357/ac0aea. S2CID 235435757. 40.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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  9. ^ Söderhjelm, Staffan (January 1999), "Visual binary orbits and masses POST HIPPARCOS", Astronomy and Astrophysics, 341: 121–140, Bibcode:1999A&A...341..121S
  10. ^ Bowman, Richard L. "Interactive Planetary Orbits - Kepler's Laws Calculations". Archived from the original on 12 December 2012. Retrieved 23 February 2012.
  11. ^ a b c Philip C. Gregory. "Additional Keplerian Signals in the HARPS data for Gliese 667C from a Bayesian Re-analysis". arXiv:1212.4058. Bibcode:2012arXiv1212.4058G. {{cite journal}}: Cite journal requires |journal= (help) Cite error: The named reference "Gregory" was defined multiple times with different content (see the help page).
  12. ^ "Habitable Planet Reality Check: GJ 667C". Drew Ex Machina. September 7, 2014.
  13. ^ a b Sven Wedemeyer-Böhm. "Life on Gliese 667Cc?". Institute of Theoretical Astrophysics. Cite error: The named reference "news" was defined multiple times with different content (see the help page).
  14. ^ "Toward spectral classification of L and T dwarfs: infrared and optical spectroscopy and analysis" (PDF), The Astrophysical Journal, The American Astronomical Society, January 2002, retrieved 2012-02-14
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  16. ^ a b c d e f g Anglada-Escudé, Guillem; Tuomi, Mikko; Gerlach, Enrico; Barnes, Rory; Heller, René; Jenkins, James S.; Wende, Sebastian; Vogt, Steven S.; Butler, R. Paul; Reiners, Ansgar; Jones, Hugh R. A. (2013-06-07). "A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone" (PDF). Astronomy & Astrophysics. arXiv:1306.6074. Bibcode:2013A&A...556A.126A. doi:10.1051/0004-6361/201321331. Archived from the original (PDF) on 2013-06-30. Retrieved 2013-06-25.
  17. ^ a b c d Feroz, F.; Hobson, M. P. (2014). "Bayesian analysis of radial velocity data of GJ667C with correlated noise: evidence for only two planets". Monthly Notices of the Royal Astronomical Society. 437 (4): 3540–3549. arXiv:1307.6984. Bibcode:2014MNRAS.437.3540F.{{cite journal}}: CS1 maint: multiple names: authors list (link) Cite error: The named reference "ferozhobson2014" was defined multiple times with different content (see the help page).
  18. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1089/ast.2010.0545, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1089/ast.2010.0545 instead.
  19. ^ a b "32 New Exoplanets Found" (Press release). ESO. 2009-10-19. Retrieved 2014-08-29. {{cite press release}}: Cite has empty unknown parameter: |authors= (help)
  20. ^ a b Makarov, Valeri V.; Berghea, Ciprian (2014). "Dynamical Evolution and Spin-orbit Resonances of Potentially Habitable Exoplanets. The Case of GJ 667C". The Astrophysical Journal. 780 (2). article id. 124. arXiv:1311.4831. Bibcode:2014ApJ...780..124M. doi:10.1088/0004-637X/780/2/124.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  21. ^ a b Bonfils, X.; Delfosse, X.; Udry, S.; Forveille, T.; Mayor, M.; Perrier, C.; Bouchy, F.; Gillon, M.; Lovis, C.; Pepe, F.; Queloz, D.; Santos, N. C.; Ségransan, D.; Bertaux, J.-L. (2013). "The HARPS search for southern extra-solar planets. XXXI. The M-dwarf sample". Astronomy & Astrophysics. 549. id.A109. arXiv:1111.5019. Bibcode:2013A&A...549A.109B. doi:10.1051/0004-6361/201014704.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  22. ^ University of Göttingen. Presseinformation: Wissenschaftler entdecken möglicherweise bewohnbare Super-Erde - Göttinger Astrophysiker untersucht Planeten in 22 Lichtjahren Entfernung. Nr. 17/2012 - 02.02.2012. Announcement on university homepage, retrieved 2012-02-02
  23. ^ a b Chow, Denise (February 2, 2012). "Newfound Alien Planet is Best Candidate Yet to Support Life, Scientists Say". Space.com. Archived from the original on 2013-04-19. Retrieved February 3, 2012. Cite error: The named reference "Space-20120202" was defined multiple times with different content (see the help page).
  24. ^ Dvorsky, George (18 December 2012). "Astronomer discovers three potentially habitable planets orbiting around one red dwarf". io9. Archived from the original on 2013-07-03. Retrieved 21 March 2013.
  25. ^ Kramer, Miriam (25 June 2013). "Found! 3 Super-Earth Planets That Could Support Alien Life". Space.com. TechMediaNetwork. Archived from the original on 2013-06-29. Retrieved 2013-06-26.

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Notes

  1. ^ Based on a calculated eccentricity value of .

Media related to Gliese 667 at Wikimedia Commons

  • "MLO 4". SolStation. Retrieved June 29, 2013.
  • exoplanet art sites:


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