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{{starbox image {{starbox image
|image = ] |image = ]
|caption = KOI-314c ''(foreground)'' and KOI-314b ''(top)'' are transiting ] orbiting the star KOI-314 ''(left)''. (Artists' conception.) |caption = KOI-314c ''(foreground)'' and KOI-314b ''(top)'' are transiting ] orbiting the star KOI-314 ''(left)''. (Artists' conception.)
|credit = Christine Pulliam/CfA |credit = Christine Pulliam/CfA
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| mass= 0.57 ± 0.05<ref name = "Pineda"/> | mass= 0.57 ± 0.05<ref name = "Pineda"/>
| radius= 0.54 ± 0.05<ref name = "Pineda"/> | radius= 0.54 ± 0.05<ref name = "Pineda"/>
| rotation = ~10 ]s<ref name = "Kipping"/> | rotation = ~10&nbsp;days<ref name = "Kipping"/>
| rotational_velocity = ~3<ref name = "Kipping"/> | rotational_velocity = ~3<ref name = "Kipping"/>
| luminosity_bolometric = 0.060 ± 0.008 <ref name = "Mann"/> | luminosity_bolometric = 0.060 ± 0.008 <ref name = "Mann"/>
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{{Starbox end}} {{Starbox end}}


'''KOI-314''', also known as '''Kepler-138''', is a ]<ref name = "Pineda">{{Cite journal | last=Pineda | first=Sebastian | coauthors = ''et al.'' | title=Using High-resolution Optical Spectra to Measure Intrinsic Properties of Low-mass Stars: New Properties for KOI-314 and GJ 3470 | journal=The Astrophysical Journal| date=21 March 2013 | doi=10.1088/0004-637X/767/1/28 | accessdate=1 March 2014|url=http://iopscience.iop.org/0004-637X/767/1/28/|arxiv = 1302.6231 |bibcode = 2013ApJ...767...28P }}</ref><ref name = "Mann">{{Cite journal | last=Mann | first=Andrew | coauthors = ''et al.'' | title=Spectro-thermometry of M Dwarfs and Their Candidate Planets: Too Hot, Too Cool, or Just Right? | journal=The Astrophysical Journal| date=4 December 2013 | doi=10.1088/0004-637X/779/2/188 | accessdate=1 March 2014|url=http://iopscience.iop.org/0004-637X/779/2/188/|arxiv = 1311.0003 |bibcode = 2013ApJ...779..188M }}</ref> located in the constellation ], 200 ] from ]<ref name = "Pineda"/>. It is located within the field of vision of the ], the satellite that ]'s ] used to detect planets that may be transiting their stars. '''KOI-314''', also known as '''Kepler-138''', is a ]<ref name = "Pineda">{{Cite journal | last=Pineda | first=Sebastian | coauthors = ''et al.'' | title=Using High-resolution Optical Spectra to Measure Intrinsic Properties of Low-mass Stars: New Properties for KOI-314 and GJ 3470 | journal=The Astrophysical Journal| date=21 March 2013 | doi=10.1088/0004-637X/767/1/28 | accessdate=1 March 2014|url=http://iopscience.iop.org/0004-637X/767/1/28/|arxiv = 1302.6231 |bibcode = 2013ApJ...767...28P }}</ref><ref name = "Mann">{{Cite journal | last=Mann | first=Andrew | coauthors = ''et al.'' | title=Spectro-thermometry of M Dwarfs and Their Candidate Planets: Too Hot, Too Cool, or Just Right? | journal=The Astrophysical Journal| date=4 December 2013 | doi=10.1088/0004-637X/779/2/188 | accessdate=1 March 2014|url=http://iopscience.iop.org/0004-637X/779/2/188/|arxiv = 1311.0003 |bibcode = 2013ApJ...779..188M }}</ref> located in the constellation ], 200 ] from ].<ref name = "Pineda"/> It is located within the field of vision of the ], the satellite that ]'s ] used to detect planets that may be transiting their stars.


The star hosts three confirmed planets, including the the lowest-mass planet with a measured mass and size discovered to date, ]<ref name = "Briefing"/><ref name = "Kipping"/><ref name = "utoday">{{cite web |url=http://www.universetoday.com/107812/kepler-finds-an-earth-sized-gas-giant/ |title=Kepler Finds an Earth-Sized “Gas Giant” |author=Jason Major |date=6 January 2014 |work= |publisher=Universe Today |accessdate=1 March 2014}}</ref>, with a mass equal to that of the ]<ref name = "Kipping"/>. ] is remarkable for resembling a miniaturized ] with a density too low for a rocky planet<ref name = "Kipping"/>, despite being the same as the Earth. The star hosts three confirmed planets, including the lowest-mass planet with a measured mass and size discovered to date, ],<ref name = "Kipping"/><ref name = "Briefing"/><ref name = "utoday">{{cite web |url=http://www.universetoday.com/107812/kepler-finds-an-earth-sized-gas-giant/ |title=Kepler Finds an Earth-Sized "Gas Giant" |author=Jason Major |date=6 January 2014 |work= |publisher=Universe Today |accessdate=1 March 2014}}</ref> with a mass equal to that of the ].<ref name = "Kipping"/> ] is remarkable for resembling a miniaturized ] with a density too low for a rocky planet,<ref name = "Kipping"/> despite being the same as the Earth.


==Nomenclature and history== ==Nomenclature and history==
Prior to Kepler observation, KOI-314 had the ] catalogue number 2MASS J19213157+4317347. In the Kepler Input Catalog it has the designation of KIC 7603200, and when it was found to have transiting planet candidates it was given the ] number of KOI-314. Prior to Kepler observation, KOI-314 had the ] catalogue number 2MASS J19213157+4317347. In the ] it has the designation of KIC 7603200, and when it was found to have transiting planet candidates it was given the ] number of KOI-314.


]'' search volume, in the context of the ].]] ]'' search volume, in the context of the ].]]


Planetary candidates were detected around the star by ]'s ], a mission tasked with discovering planets in ] around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of ], although other phenomenon can also be responsible which is why the term planetary candidate is used<ref name = "Morton">{{Cite journal | last=Morton | first=Timothy | year=2011 | last2=Johnson | first2=John | title=On the Low False Positive Probabilities of Kepler Planet Candidates | journal=The Astrophysical Journal| date=23 August 2011 | doi=10.1088/0004-637X/738/2/170 | accessdate=2 March 2014|url=http://iopscience.iop.org/0004-637X/738/2/170/|arxiv = 1101.5630 |bibcode = 2011ApJ...738..170M }}</ref>. By timing these dips, ] were detected between two of the candidates<ref name = "Kipping">{{Cite journal | last=Kipping | first=David | authorlink=David Kipping | coauthors = ''et al.'' | title=The Hunt for Exomoons with Kepler (HEK): IV. A Search for Moons around Eight M-Dwarfs | journal=The Astrophysical Journal| date=1 March 2014 | doi=10.1088/0004-637X/784/1/28 | accessdate=1 March 2014|url=http://iopscience.iop.org/0004-637X/784/1/28/|arxiv = 1401.1210 |bibcode = 2014ApJ...784..28K }}</ref>, allowing for a measurement of their masses and confirmation as real planets given that the masses were significantly below the deuterium burning limits<ref>{{cite web|date=28 February 2003|title=Working Group on Extrasolar Planets: Definition of a "Planet"|url=http://www.dtm.ciw.edu/boss/definition.html|work=IAU position statement|accessdate=2006-09-09}}</ref>. Planetary candidates were detected around the star by ]'s ], a mission tasked with discovering planets in ] around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of ], although other phenomenon can also be responsible which is why the term planetary candidate is used.<ref name = "Morton">{{Cite journal | last=Morton | first=Timothy | last2=Johnson | first2=John | title=On the Low False Positive Probabilities of Kepler Planet Candidates | journal=The Astrophysical Journal| date=23 August 2011 | doi=10.1088/0004-637X/738/2/170 | accessdate=2 March 2014|url=http://iopscience.iop.org/0004-637X/738/2/170/|arxiv = 1101.5630 |bibcode = 2011ApJ...738..170M }}</ref> By timing these dips, ] were detected between two of the candidates,<ref name = "Kipping">{{Cite journal | last=Kipping | first=David | authorlink=David Kipping | coauthors = ''et al.'' | title=The Hunt for Exomoons with Kepler (HEK): IV. A Search for Moons around Eight M-Dwarfs | journal=The Astrophysical Journal| date=1 March 2014 | doi=10.1088/0004-637X/784/1/28 | accessdate=1 March 2014|url=http://iopscience.iop.org/0004-637X/784/1/28/|arxiv = 1401.1210 |bibcode = 2014ApJ...784..28K }}</ref> allowing for a measurement of their masses and confirmation as real planets given that the masses were significantly below the deuterium burning limits.<ref>{{cite web|date=28 February 2003|title=Working Group on Extrasolar Planets: Definition of a "Planet"|url=http://www.dtm.ciw.edu/boss/definition.html|work=IAU position statement|accessdate=2006-09-09}}</ref>


Following the acceptance of the discovery paper, the Kepler team provided an additional moniker for the system of "Kepler-138" <ref name = "keplernames">{{cite web |url=http://kepler.nasa.gov/Mission/discoveries/ |title=Kepler – Discoveries – Summary Table |author=] | date=27 January 2014 |work= |publisher=] |accessdate=1 March 2014}}</ref>. However, the planets were discovered by scientists outside of the Kepler team<ref name = "Kipping"/> and naming precedent belongs to the original discoverers (who refer to the star as KOI-314<ref name = "Kipping"/><ref name = "Briefing">{{cite web |url=http://www.youtube.com/watch?v=9jNcfRsUK8o |title=David Kipping - Press Briefing on First Earth-Mass Transiting Planet, KOI-314c |author=David Kipping | authorlink=David Kipping | date=26 January 2014 | work= | publisher=YouTube | accessdate=1 March 2014}}</ref>), unless the discoverers provide formal agreement for a change of name<ref name = "IAUnaming">{{cite web|title=Public Naming of Planets and Planetary Satellites|url=http://www.iau.org/static/public/naming/planets_and_satellites.pdf|publisher=]|accessdate=2013-08-19}}</ref>. Following the acceptance of the discovery paper, the Kepler team provided an additional moniker for the system of "Kepler-138".<ref name = "keplernames">{{cite web |url=http://kepler.nasa.gov/Mission/discoveries/ |title=Kepler – Discoveries – Summary Table |author=] | date=27 January 2014 |work= |publisher=] |accessdate=1 March 2014}}</ref> However, the planets were discovered by scientists outside of the Kepler team<ref name = "Kipping"/> and naming precedent belongs to the original discoverers (who refer to the star as KOI-314<ref name = "Kipping"/><ref name = "Briefing">{{cite web |url=http://www.youtube.com/watch?v=9jNcfRsUK8o |title=David Kipping - Press Briefing on First Earth-Mass Transiting Planet, KOI-314c |author=David Kipping | authorlink=David Kipping | date=26 January 2014 | work= | publisher=YouTube | accessdate=1 March 2014}}</ref>), unless the discoverers provide formal agreement for a change of name.<ref name = "IAUnaming">{{cite web|title=Public Naming of Planets and Planetary Satellites|url=http://www.iau.org/static/public/naming/planets_and_satellites.pdf|publisher=]|accessdate=2013-08-19}}</ref>


Candidate planets are conventionally assigned the designations ".01", ".02", ".03", etc after the star's name, in the order of discovery<ref name = "kepler-catalogue"/>. If planets candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest<ref name = "kepler-catalogue"/>. Following these rules, the first two candidate planets were detected simultaneously<ref name = "Borucki">{{Cite journal | last=Borucki | first=William J. | authorlink=William J. Borucki | coauthors = ''et al.'' | year=2011| title=Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data | journal=The Astrophysical Journal| date=29 June 2011 | doi=10.1088/0004-637X/736/1/19 | accessdate=2 March 2014|url=http://iopscience.iop.org/0004-637X/736/1/19/|arxiv = 1102.0541 |bibcode = 2011ApJ...736...19B }}</ref> and assigned the names KOI-314.01 and KOI-314.02, with respective orbital periods of 13.8 and 23.1 days<ref name = "Borucki"/>. Over a year later later, a much smaller planet candidate was detected and assigned the name KOI-314.03<ref name = "Batalha">{{Cite journal | last=Batalha | first=Natalie | coauthors = ''et al.'' | year=2013| title=Planetary Candidates Observed by Kepler. III. Analysis of the First 16 Months of Data | journal=The Astrophysical Journal Supplement| date=5 February 2013 | doi=10.1088/0067-0049/204/2/24 | accessdate=2 March 2014|url=http://iopscience.iop.org/0067-0049/204/2/24/|arxiv = 1202.5852 |bibcode = 2013ApJS..204...24B }}</ref>, despite being the shortest orbital period planet (period of 10.3 days) found to date. Candidate planets are conventionally assigned the designations ".01", ".02", ".03", etc. after the star's name, in the order of discovery.<ref name = "kepler-catalogue"/> If planets candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest.<ref name = "kepler-catalogue"/> Following these rules, the first two candidate planets were detected simultaneously<ref name = "Borucki">{{Cite journal | last=Borucki | first=William J. | authorlink=William J. Borucki | coauthors = ''et al.'' | title=Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data | journal=The Astrophysical Journal| date=29 June 2011 | doi=10.1088/0004-637X/736/1/19 | accessdate=2 March 2014|url=http://iopscience.iop.org/0004-637X/736/1/19/|arxiv = 1102.0541 |bibcode = 2011ApJ...736...19B }}</ref> and assigned the names KOI-314.01 and KOI-314.02, with respective orbital periods of 13.8 and 23.1&nbsp;days.<ref name = "Borucki"/> Over a year later later, a much smaller planet candidate was detected and assigned the name KOI-314.03,<ref name = "Batalha">{{Cite journal | last=Batalha | first=Natalie | coauthors = ''et al.'' | title=Planetary Candidates Observed by Kepler. III. Analysis of the First 16 Months of Data | journal=The Astrophysical Journal Supplement| date=5 February 2013 | doi=10.1088/0067-0049/204/2/24 | accessdate=2 March 2014|url=http://iopscience.iop.org/0067-0049/204/2/24/|arxiv = 1202.5852 |bibcode = 2013ApJS..204...24B }}</ref> despite being the shortest orbital period planet (period of 10.3&nbsp;days) found to date.


Confirmed planets are conventionally assigned the designations ''b'', ''c'', ''d'', etc after the star's name<ref name="planetnaming">{{cite arxiv |title=On the naming convention used for multiple star systems and extrasolar planets |year=2010 |last1=Hessman |first1=F. V. |last2=Dhillon |first2=V. S. |last3=Winget |first3=D. E. |last4=Schreiber |first4=M. R. |last5=Horne |first5=K. |last6=Marsh |first6=T. R. |last7=Guenther |first7=E. |last8=Schwope |first8=A. |last9=Heber |first9=U. |eprint=1012.0707|bibcode = 2010arXiv1012.0707H |class=astro-ph.SR }}</ref>. The labels are assigned alphabetically in the order of discovery starting from ''b''<ref name = "planetnaming"/>. Since KOI-314.01 and KOI-314.02 were confirmed as planets simultaneously, the alphabetical names were assigned in order of orbital period by the discoverers<ref name = "Kipping"/>, and thus became KOI-314b and KOI-314c respectively. Since no ] were detected due to KOI-314.03, this planetary candidate remained unconfirmed as 6 January 2014 and thus kept the same name<ref name = "Kipping"/>. Confirmed planets are conventionally assigned the designations ''b'', ''c'', ''d'', etc. after the star's name.<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |year=2010 |last1=Hessman |first1=F. V. |last2=Dhillon |first2=V. S. |last3=Winget |first3=D. E. |last4=Schreiber |first4=M. R. |last5=Horne |first5=K. |last6=Marsh |first6=T. R. |last7=Guenther |first7=E. |last8=Schwope |first8=A. |last9=Heber |first9=U. |eprint=1012.0707|bibcode = 2010arXiv1012.0707H |class=astro-ph. SR }}</ref> The labels are assigned alphabetically in the order of discovery starting from ''b''.<ref name = "planetnaming"/> Since KOI-314.01 and KOI-314.02 were confirmed as planets simultaneously, the alphabetical names were assigned in order of orbital period by the discoverers,<ref name = "Kipping"/> and thus became KOI-314b and KOI-314c respectively. Since no ] were detected due to KOI-314.03, this planetary candidate remained unconfirmed as 6 January 2014 and thus kept the same name.<ref name = "Kipping"/>


In the following weeks, on 28 February 2014, a new paper validated KOI-314.03 as being a real planet with a false alarm probability of less than 1%<ref name="Rowe">{{cite arxiv |title=Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems |year=2014 | coauthors = ''et al.'' | eprint=1402.6534|bibcode = 2014arXiv1402.6534R |class=astro-ph.EP }}</ref>. The new paper used different names for the planets, going from KOI-314b to Kepler-138c, KOI-314c to Kepler-138d and KOI-314.03 to Kepler-138b<ref name = "Rowe"/>. Since KOI-314b and KOI-314c had been discovered in an earlier published article,<ref name = "Kipping"/> naming precedent belongs to the original paper and thus KOI-314b and c cannot be renamed without formal agreement by the discoverers<ref name = "IAUnaming"/>. However, KOI-314.03 was confirmed only in the later paper meaning this planet's name is given by the discoverers in the second paper, who use Kepler-138b. This has led to the unusual situation of having one star with two ''b'' planets in orbit and two different base-names for the orbiting planets. In the following weeks, on 28 February 2014, a new paper validated KOI-314.03 as being a real planet with a false alarm probability of less than 1%.<ref name="Rowe">{{cite arXiv |title=Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems |year=2014 | coauthors = ''et al.'' | eprint=1402.6534|bibcode = 2014arXiv1402.6534R |class=astro-ph. EP }}</ref> The new paper used different names for the planets, going from KOI-314b to Kepler-138c, KOI-314c to Kepler-138d and KOI-314.03 to Kepler-138b.<ref name = "Rowe"/> Since KOI-314b and KOI-314c had been discovered in an earlier published article,<ref name = "Kipping"/> naming precedent belongs to the original paper and thus KOI-314b and c cannot be renamed without formal agreement by the discoverers.<ref name = "IAUnaming"/> However, KOI-314.03 was confirmed only in the later paper meaning this planet's name is given by the discoverers in the second paper, who use Kepler-138b. This has led to the unusual situation of having one star with two ''b'' planets in orbit and two different base-names for the orbiting planets.


==Stellar characteristics== ==Stellar characteristics==
KOI-314 is a ] star that is approximately 57% the mass of and 54% the radius of the ]<ref name = "Pineda"/>. It has a surface temperature of 3871 ± 58 ]<ref name=Mann />. In comparison, the Sun has a surface temperature of 5778 K<ref>{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=15 September 2008 |work= |publisher=Universe Today |accessdate=19 February 2011}}</ref>. The star's ], or how bright it appears from Earth's perspective, is 12.925<ref name = "kepler-catalogue"/>. Therefore, it is too dim to be seen with the naked eye. KOI-314 is a ] star that is approximately 57% the mass of and 54% the radius of the ].<ref name = "Pineda"/> It has a surface temperature of 3871 ± 58 ].<ref name=Mann /> In comparison, the Sun has a surface temperature of 5778 K.<ref>{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=15 September 2008 |work= |publisher=Universe Today |accessdate=19 February 2011}}</ref> The star's ], or how bright it appears from Earth's perspective, is 12.925.<ref name = "kepler-catalogue"/> Therefore, it is too dim to be seen with the naked eye.


== Planetary system == == Planetary system ==


All known planets ] the star; this means that all three planets' orbits appear to cross in front of their star as viewed from the Earth's perspective. Their ]s relative to Earth's line of sight, or how far above or below the plane of sight they are, vary by less than one degree. This allows direct measurements of the planets' periods and relative diameters (compared to the host star) by monitoring each planet's transit of the star<ref name = "Kipping"/><ref name = "Rowe"/>. All known planets ] the star; this means that all three planets' orbits appear to cross in front of their star as viewed from the Earth's perspective. Their ]s relative to Earth's line of sight, or how far above or below the plane of sight they are, vary by less than one degree. This allows direct measurements of the planets' periods and relative diameters (compared to the host star) by monitoring each planet's transit of the star.<ref name = "Kipping"/><ref name = "Rowe"/>


Whilst the inner most planet has a size slightly larger than the ], KOI-314b and c both have a radius of 1.6 ]<ref name = "Kipping"/><ref name = "Rowe"/>. All of the planets are too close to their star to be considered within the ]<ref name = "Briefing"/>. Although KOI-314b and c have the same size, their masses and densities vary greatly. Of these two, the inner planet is consistent with a rocky ], whereas the outer planet is thought to have a significant gas envelope and low density, resembling a miniaturized ]<ref name = "Kipping"/>. The striking differences between these two planets have been hypothesized to be due ]<ref name = "Kipping"/>. Whilst the inner most planet has a size slightly larger than the ], KOI-314b and c both have a radius of 1.6 ].<ref name = "Kipping"/><ref name = "Rowe"/> All of the planets are too close to their star to be considered within the ].<ref name = "Briefing"/> Although KOI-314b and c have the same size, their masses and densities vary greatly. Of these two, the inner planet is consistent with a rocky ], whereas the outer planet is thought to have a significant gas envelope and low density, resembling a miniaturized ].<ref name = "Kipping"/> The striking differences between these two planets have been hypothesized to be due ].<ref name = "Kipping"/>


{{Auto images {{Auto images
|title=<center>''KOI-314'' Comparisons</center> |align=center|total_width=800|width1=3000|height1=2000|image1=KOI-314c_Size_Comparison_to_the_Earth.jpg|caption1=Comparison of the size of the planet ] and the ]. |width2=2500|height2=2250|image2=KOI-314_mass-radius_comparison_chart.jpg |caption2=Mass-Radius plot of all exoplanets with a measured mass and size, highlighting the planets ] and ]. }} |title=<center>''KOI-314'' Comparisons</center> |align=center|total_width=800|width1=3000|height1=2000|image1=KOI-314c_Size_Comparison_to_the_Earth.jpg|caption1=Comparison of the size of the planet ] and the ]. |width2=2500|height2=2250|image2=KOI-314_mass-radius_comparison_chart.jpg |caption2=Mass-Radius plot of all exoplanets with a measured mass and size, highlighting the planets ] and ]. }}


{| class="toccolours sortable" border=1 cellspacing=0 cellpadding=2 align=center style="text-align:center; border-collapse:collapse; margin-left: 0; margin-right: auto; border: 1px solid darkgray;" {| class="toccolours sortable" border=1 cellspacing=0 cellpadding=2 align=center style="text-align:center; border-collapse:collapse; margin-left: 0; margin-right: auto; border: 1px solid darkgray;"
Line 85: Line 85:
! ] <small>(])</small> ! ] <small>(])</small>
|-style="border: 1px solid darkgray;" |-style="border: 1px solid darkgray;"
! ] ! ]
|| 3.8 ± 1.4 || 0.093 ± 0.0027 ||13.7816 ± 0.0002 || 0.050 ± 0.049 || 70 ± 50 || 88.5 ± 0.2 || 1.61 ± 0.16 || 3.8 ± 1.4 || 0.093 ± 0.0027 ||13.7816 ± 0.0002 || 0.050 ± 0.049 || 70 ± 50 || 88.5 ± 0.2 || 1.61 ± 0.16
|-style="border: 1px solid darkgray;" |-style="border: 1px solid darkgray;"
! ] ! ]
|| 1.0 ± 0.4 || 0.132 ± 0.038 ||23.0893 ± 0.0007 || 0.024 ± 0.024 || 170 ± 130 || 88.8 ± 0.1 || 1.61 ± 0.16 || 1.0 ± 0.4 || 0.132 ± 0.038 ||23.0893 ± 0.0007 || 0.024 ± 0.024 || 170 ± 130 || 88.8 ± 0.1 || 1.61 ± 0.16
|-style="border: 1px solid darkgray;" |-style="border: 1px solid darkgray;"
! ] ! ]
|| - || 0.0769 ± 0.0022 ||10.31292 ± 0.00006|| - || - || 89.5 ± 0.5 || 0.45 ± 0.06 || - || 0.0769 ± 0.0022 ||10.31292 ± 0.00006|| - || - || 89.5 ± 0.5 || 0.45 ± 0.06
|-style="border: 1px solid darkgray;" |-style="border: 1px solid darkgray;"
Line 97: Line 97:


== See also == == See also ==
* ] *]
* ] *]
* ] *]


== Notes == == Notes ==
Line 109: Line 109:


==External links == ==External links ==
{{Commons category}} {{Commons category}}
* - ]. * - ].
* – ]. * – ].
* – ]. * – ].
* – ]. * – ].
* *
{{Stars of Lyra}} {{Stars of Lyra}}
{{exoplanets}} {{exoplanets}}

Revision as of 19:56, 2 March 2014

KOI-314
File:KOI-314c Artistic Impression.jpg
KOI-314c (foreground) and KOI-314b (top) are transiting exoplanets orbiting the star KOI-314 (left). (Artists' conception.)
Credit: Christine Pulliam/CfA
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension 19 21 31.563
Declination +43° 17′ 34.76″
Apparent magnitude (V) 12.925 (Kepler band)
Characteristics
Spectral type M0V
Astrometry
Distance217 ± 24 ly
(66.5 ± 7.3 pc)
Details
Mass0.57 ± 0.05 M☉
Radius0.54 ± 0.05 R☉
Luminosity (bolometric)0.060 ± 0.008  L☉
Surface gravity (log g)4.74 ± 0.09 cgs
Temperature3871 ± 58 K
Metallicity -0.28 ± 0.10 dex
Rotation~10 days
Rotational velocity (v sin i)~3 km/s
Age>1 Gyr
Other designations
Kepler-138, KIC 7603200, 2MASS J19213157+4317347
Database references
SIMBADdata

KOI-314, also known as Kepler-138, is a red dwarf located in the constellation Lyra, 200 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission used to detect planets that may be transiting their stars.

The star hosts three confirmed planets, including the lowest-mass planet with a measured mass and size discovered to date, KOI-314c, with a mass equal to that of the Earth. KOI-314c is remarkable for resembling a miniaturized gas giant with a density too low for a rocky planet, despite being the same as the Earth.

Nomenclature and history

Prior to Kepler observation, KOI-314 had the 2MASS catalogue number 2MASS J19213157+4317347. In the Kepler Input Catalog it has the designation of KIC 7603200, and when it was found to have transiting planet candidates it was given the Kepler object of interest number of KOI-314.

The Kepler Space Telescope search volume, in the context of the Milky Way Galaxy.

Planetary candidates were detected around the star by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of Earth, although other phenomenon can also be responsible which is why the term planetary candidate is used. By timing these dips, gravitational interactions were detected between two of the candidates, allowing for a measurement of their masses and confirmation as real planets given that the masses were significantly below the deuterium burning limits.

Following the acceptance of the discovery paper, the Kepler team provided an additional moniker for the system of "Kepler-138". However, the planets were discovered by scientists outside of the Kepler team and naming precedent belongs to the original discoverers (who refer to the star as KOI-314), unless the discoverers provide formal agreement for a change of name.

Candidate planets are conventionally assigned the designations ".01", ".02", ".03", etc. after the star's name, in the order of discovery. If planets candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest. Following these rules, the first two candidate planets were detected simultaneously and assigned the names KOI-314.01 and KOI-314.02, with respective orbital periods of 13.8 and 23.1 days. Over a year later later, a much smaller planet candidate was detected and assigned the name KOI-314.03, despite being the shortest orbital period planet (period of 10.3 days) found to date.

Confirmed planets are conventionally assigned the designations b, c, d, etc. after the star's name. The labels are assigned alphabetically in the order of discovery starting from b. Since KOI-314.01 and KOI-314.02 were confirmed as planets simultaneously, the alphabetical names were assigned in order of orbital period by the discoverers, and thus became KOI-314b and KOI-314c respectively. Since no gravitational interactions were detected due to KOI-314.03, this planetary candidate remained unconfirmed as 6 January 2014 and thus kept the same name.

In the following weeks, on 28 February 2014, a new paper validated KOI-314.03 as being a real planet with a false alarm probability of less than 1%. The new paper used different names for the planets, going from KOI-314b to Kepler-138c, KOI-314c to Kepler-138d and KOI-314.03 to Kepler-138b. Since KOI-314b and KOI-314c had been discovered in an earlier published article, naming precedent belongs to the original paper and thus KOI-314b and c cannot be renamed without formal agreement by the discoverers. However, KOI-314.03 was confirmed only in the later paper meaning this planet's name is given by the discoverers in the second paper, who use Kepler-138b. This has led to the unusual situation of having one star with two b planets in orbit and two different base-names for the orbiting planets.

Stellar characteristics

KOI-314 is a M-type star that is approximately 57% the mass of and 54% the radius of the Sun. It has a surface temperature of 3871 ± 58 K. In comparison, the Sun has a surface temperature of 5778 K. The star's apparent magnitude, or how bright it appears from Earth's perspective, is 12.925. Therefore, it is too dim to be seen with the naked eye.

Planetary system

All known planets transit the star; this means that all three planets' orbits appear to cross in front of their star as viewed from the Earth's perspective. Their inclinations relative to Earth's line of sight, or how far above or below the plane of sight they are, vary by less than one degree. This allows direct measurements of the planets' periods and relative diameters (compared to the host star) by monitoring each planet's transit of the star.

Whilst the inner most planet has a size slightly larger than the Moon, KOI-314b and c both have a radius of 1.6 Earth radii. All of the planets are too close to their star to be considered within the habitable zone. Although KOI-314b and c have the same size, their masses and densities vary greatly. Of these two, the inner planet is consistent with a rocky Super Earth, whereas the outer planet is thought to have a significant gas envelope and low density, resembling a miniaturized gas giant. The striking differences between these two planets have been hypothesized to be due photoevaporation.

KOI-314 Comparisons
File:KOI-314c Size Comparison to the Earth.jpgComparison of the size of the planet KOI-314c and the Earth.File:KOI-314 mass-radius comparison chart.jpgMass-Radius plot of all exoplanets with a measured mass and size, highlighting the planets KOI-314b and KOI-314c.
The KOI-314 system
Planet
(in order of discovery) 		Mass (ME) Semimajor
axis (AU) 		Orbital period (d) e ω(deg) Inclination (°) Radius (RE)
KOI-314b 3.8 ± 1.4 0.093 ± 0.0027 13.7816 ± 0.0002 0.050 ± 0.049 70 ± 50 88.5 ± 0.2 1.61 ± 0.16
KOI-314c 1.0 ± 0.4 0.132 ± 0.038 23.0893 ± 0.0007 0.024 ± 0.024 170 ± 130 88.8 ± 0.1 1.61 ± 0.16
Kepler-138b - 0.0769 ± 0.0022 10.31292 ± 0.00006 - - 89.5 ± 0.5 0.45 ± 0.06

See also

Notes

References

  1. ^ 7603200&action=Search "Kepler Input Catalog search result". Space Telescope Science Institute. Retrieved 1 March 2014. {{cite web}}: Check |url= value (help)
  2. ^ Pineda, Sebastian (21 March 2013). "Using High-resolution Optical Spectra to Measure Intrinsic Properties of Low-mass Stars: New Properties for KOI-314 and GJ 3470". The Astrophysical Journal. arXiv:1302.6231. Bibcode:2013ApJ...767...28P. doi:10.1088/0004-637X/767/1/28. Retrieved 1 March 2014. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Mann, Andrew (4 December 2013). "Spectro-thermometry of M Dwarfs and Their Candidate Planets: Too Hot, Too Cool, or Just Right?". The Astrophysical Journal. arXiv:1311.0003. Bibcode:2013ApJ...779..188M. doi:10.1088/0004-637X/779/2/188. Retrieved 1 March 2014. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ Kipping, David (1 March 2014). "The Hunt for Exomoons with Kepler (HEK): IV. A Search for Moons around Eight M-Dwarfs". The Astrophysical Journal. arXiv:1401.1210. Bibcode:2014ApJ...784..28K. doi:10.1088/0004-637X/784/1/28. Retrieved 1 March 2014. {{cite journal}}: Check |bibcode= length (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ David Kipping (26 January 2014). "David Kipping - Press Briefing on First Earth-Mass Transiting Planet, KOI-314c". YouTube. Retrieved 1 March 2014.
  6. Jason Major (6 January 2014). "Kepler Finds an Earth-Sized "Gas Giant"". Universe Today. Retrieved 1 March 2014.
  7. Morton, Timothy; Johnson, John (23 August 2011). "On the Low False Positive Probabilities of Kepler Planet Candidates". The Astrophysical Journal. arXiv:1101.5630. Bibcode:2011ApJ...738..170M. doi:10.1088/0004-637X/738/2/170. Retrieved 2 March 2014.
  8. "Working Group on Extrasolar Planets: Definition of a "Planet"". IAU position statement. 28 February 2003. Retrieved 2006-09-09.
  9. NASA (27 January 2014). "Kepler – Discoveries – Summary Table". NASA. Retrieved 1 March 2014.
  10. ^ "Public Naming of Planets and Planetary Satellites" (PDF). International Astronomical Union. Retrieved 2013-08-19.
  11. ^ Borucki, William J. (29 June 2011). "Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data". The Astrophysical Journal. arXiv:1102.0541. Bibcode:2011ApJ...736...19B. doi:10.1088/0004-637X/736/1/19. Retrieved 2 March 2014. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  12. Batalha, Natalie (5 February 2013). "Planetary Candidates Observed by Kepler. III. Analysis of the First 16 Months of Data". The Astrophysical Journal Supplement. arXiv:1202.5852. Bibcode:2013ApJS..204...24B. doi:10.1088/0067-0049/204/2/24. Retrieved 2 March 2014. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  13. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 . {{cite arXiv}}: Unknown parameter |bibcode= ignored (help)
  14. ^ A bot will complete this citation soon. Click here to jump the queue arXiv:1402.6534.
  15. Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.

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