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| {{Update|reason=The system has been remeasured, with significant new findings about the orbiting planets. |date=December 2022}} | |||
| {{Use dmy dates|date=March 2014}} | {{Use dmy dates|date=March 2014}} | ||
| {{Short description|Red dwarf in the constellation Lyra}} | {{Short description|Red dwarf in the constellation Lyra}} | ||
| Line 5: | Line 4: | ||
| | name = Kepler-138 | | name = Kepler-138 | ||
| }} | }} | ||
| {{Starbox image | |||
| | image = ] | |||
| | image = | |||
| | caption = Artist's impression of the planets orbiting Kepler-138 | |||
| | caption = <!--KOI-314c ''(foreground)'' and KOI-314b ''(top)'' are transiting ] orbiting the star KOI-314 ''(left)''. (Artists' conception.) --> | |||
| }} | |||
| {{Starbox observe | {{Starbox observe | ||
| | epoch = J2000 | | epoch = J2000 | ||
| Line 13: | Line 13: | ||
| | ra = {{RA|19|21|31.56798}}<ref name="GaiaDR3"/> | | ra = {{RA|19|21|31.56798}}<ref name="GaiaDR3"/> | ||
| | dec = {{DEC|+43|17|34.6810}}<ref name="GaiaDR3"/> | | dec = {{DEC|+43|17|34.6810}}<ref name="GaiaDR3"/> | ||
| | appmag_v = {{val|13.040|0.092}}<ref name="NASAExoplanetArchive"/> | |||
| ⚫ | |||
| }} | }} | ||
| {{Starbox character | {{Starbox character | ||
| | class= M1V<ref name = "Pineda"/> | | class= M1V<ref name = "Pineda"/> | ||
| | g-r= 1.121<ref name = "kepler-catalogue"/> | | g-r= 1.121<ref name = "kepler-catalogue"/> | ||
| | appmag_1_passband = V | |||
| | appmag_1 = {{val|13.040|0.092}}<ref name="NASAExoplanetArchive"/> | |||
| | appmag_2_passband = Kepler | |||
| | appmag_2 = 12.925<ref name="kepler-catalogue"/> | |||
| }} | }} | ||
| {{Starbox astrometry | {{Starbox astrometry | ||
| Line 30: | Line 34: | ||
| }} | }} | ||
| {{Starbox detail | {{Starbox detail | ||
| | mass = {{val|0.535|0.012}}<ref name="Piaulet2022"/> | |||
| ⚫ | |||
| | radius = 0. |
| radius = {{val|0.535|0.013|0.014}}<ref name="Piaulet2022"/> | ||
| | luminosity_bolometric = 0. |
| luminosity_bolometric = {{val|0.056|0.004}}<ref name="Piaulet2022"/> | ||
| | luminosity_visual = 0.026 ± 0.006 | | luminosity_visual = 0.026 ± 0.006 | ||
| | temperature = |
| temperature = {{val|3726|44|40}}<ref name=Mann2017/> | ||
| | gravity = 4. |
| gravity = {{val|4.71|0.03}}<ref name="Piaulet2022"/> | ||
| | metal_fe = -0.28 ± 0.10<ref name="Pineda" /> | | metal_fe = -0.28 ± 0.10<ref name="Pineda" /> | ||
| | rotation = {{val|19.394|0.013|s= days}}<ref name="McQuillan2013"/> | | rotation = {{val|19.394|0.013|s= days}}<ref name="McQuillan2013"/> | ||
| Line 52: | Line 56: | ||
| {{Starbox end}} | {{Starbox end}} | ||
| '''Kepler-138''', also known as '''KOI-314''', is a ]<ref name = "Pineda" |
'''Kepler-138''', also known as '''KOI-314''', is a ]<ref name = "Pineda"/><ref name = "Mann"/> located in the constellation ], 219 ] from ].<ref name="GaiaDR3"/> It is located within the field of vision of the ], the satellite that ]'s ] used to detect planets ] their stars. | ||
| The star hosts three confirmed planets, including the lowest-mass |
The star hosts three confirmed planets and a likely fourth, including the lowest-mass ] with a measured mass and size discovered to date, Kepler-138b,<ref name = "Jontof-Hutter"/> with a mass comparable to that of ]. Kepler-138d is remarkable for its low density; initially thought likely to be a ],<ref name = "Kipping"/> more recent observations as of 2022 show that it, as well as planet c, are likely to be ]s.<ref name="NASA2022"/><ref>{{cite web |url=https://arstechnica.com/science/2022/12/scientists-revisit-kepler-findings-learn-two-planets-are-water-worlds/ |title=Scientists may have found the first water worlds |last=Timmer |first=John |date=15 December 2022 |website=] |access-date=17 December 2022}}</ref> | ||
| ==Nomenclature and history== | ==Nomenclature and history== | ||
| Line 60: | Line 64: | ||
| 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. | 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. | ||
| 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 |
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 phenomena can also be responsible which is why the term planetary candidate is used.<ref name = "Morton">{{Cite journal | last1=Morton | first1=Timothy | last2=Johnson | first2=John | title=On the Low False Positive Probabilities of Kepler Planet Candidates | journal=The Astrophysical Journal| volume=738 | issue=2 | pages=170 | date=23 August 2011 | doi=10.1088/0004-637X/738/2/170 |arxiv = 1101.5630 |bibcode = 2011ApJ...738..170M | s2cid=35223956 }}</ref> By timing these dips, ] were detected between two of the candidates,<ref name = "Kipping"/> 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 |access-date=9 September 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060916161707/http://www.dtm.ciw.edu/boss/definition.html |archive-date=16 September 2006 }}</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/ |archive-url=https://web.archive.org/web/20100527104316/http://kepler.nasa.gov/Mission/discoveries/ |url-status=dead |archive-date=27 May 2010 |title=Kepler – Discoveries – Summary Table |author=NASA | date=27 January 2014 |publisher=] |access-date=1 March 2014|author-link=NASA }}</ref> However, the planets were discovered by scientists outside of the Kepler team |
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/ |archive-url=https://web.archive.org/web/20100527104316/http://kepler.nasa.gov/Mission/discoveries/ |url-status=dead |archive-date=27 May 2010 |title=Kepler – Discoveries – Summary Table |author=NASA | date=27 January 2014 |publisher=] |access-date=1 March 2014|author-link=NASA }}</ref> However, the planets were discovered by scientists outside of the Kepler team who referred to the star as KOI-314, as the Kepler designation had not been assigned yet.<ref name = "Kipping"/><ref name = "Briefing">{{cite web |url=https://www.youtube.com/watch?v=9jNcfRsUK8o |title=David Kipping - Press Briefing on First Earth-Mass Transiting Planet, KOI-314c |author=David Kipping | date=26 January 2014 | publisher=] | access-date=1 March 2014}}</ref> | ||
| Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations ".01", ".02", ".03", etc. after the star's name, in the order of discovery.<ref name = "kepler-catalogue"/> If |
Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations ".01", ".02", ".03", etc. after the star's name, in the order of discovery.<ref name = "kepler-catalogue"/> If planet 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 |last1=Borucki |first1=William J. |author-link=William J. Borucki |title=Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data |journal=The Astrophysical Journal |volume=736 |issue=1 |pages=19 |date=29 June 2011 |doi=10.1088/0004-637X/736/1/19 |arxiv=1102.0541 |bibcode=2011ApJ...736...19B |last2=Koch |first2=David G. |last3=Batalha |first3=Natalie |last4=Brown |first4=Timothy M. |last5=Bryson |first5=Stephen T. |last6=Caldwell |first6=Douglas |last7=Christensen-Dalsgaard |first7=Jørgen |last8=Cochran |first8=William D. |last9=Devore |first9=Edna |last10=Dunham |first10=Edward W. |last11=Gautier |first11=Thomas N. |last12=Geary |first12=John C. |last13=Gilliland |first13=Ronald |last14=Gould |first14=Alan |last15=Howell |first15=Steve B. |last16=Jenkins |first16=Jon M. |last17=Latham |first17=David W. |last18=Lissauer |first18=Jack J. |last19=Marcy |first19=Geoffrey W. |last20=Rowe |first20=Jason |last21=Sasselov |first21=Dimitar |last22=Boss |first22=Alan |last23=Charbonneau |first23=David |last24=Ciardi |first24=David |last25=Doyle |first25=Laurance |last26=Dupree |first26=Andrea K. |last27=Ford |first27=Eric B. |last28=Fortney |first28=Jonathan |last29=Holman |first29=Matthew J. |s2cid=15233153 |display-authors=etal}}</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, a much smaller planet candidate was detected and assigned the name KOI-314.03,<ref name = "Batalha">{{Cite journal |last1=Batalha |first1=Natalie |title=Planetary Candidates Observed by Kepler. III. Analysis of the First 16 Months of Data |journal=The Astrophysical Journal Supplement |volume=204 |issue=2 |pages=24 |date=5 February 2013 |doi=10.1088/0067-0049/204/2/24 |arxiv=1202.5852 |bibcode=2013ApJS..204...24B |last2=Rowe |first2=Jason F. |last3=Barclay |first3=Thomas |last4=Burke |first4=Christopher J. |last5=Caldwell |first5=Douglas A. |last6=Christiansen |first6=Jessie L. |last7=Mullally |first7=Fergal |last8=Thompson |first8=Susan E. |last9=Brown |first9=Timothy M. |last10=Dupree |first10=Andrea K. |last11=Fabrycky |first11=Daniel C. |last12=Ford |first12=Eric B. |last13=Fortney |first13=Jonathan J. |last14=Gilliland |first14=Ronald L. |last15=Isaacson |first15=Howard |last16=Latham |first16=David W. |last17=Marcy |first17=Geoffrey W. |last18=Quinn |first18=Samuel N. |last19=Ragozzine |first19=Darin |last20=Shporer |first20=Avi |last21=Borucki |first21=William J. |last22=Ciardi |first22=David R. |last23=Gautier |first23=Thomas N. |last24=Haas |first24=Michael R. |last25=Jenkins |first25=Jon M. |last26=Koch |first26=David G. |last27=Lissauer |first27=Jack J. |last28=Rapin |first28=William |last29=Basri |first29=Gibor S. |s2cid=19023502 |display-authors=etal}}</ref> despite being the shortest orbital period planet (period of 10.3 days) found in the system. | ||
| 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 |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 |date=2010 |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 |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 |date=2010 |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" |
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"/> 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"/> These designations have been used by subsequent studies, and by databases such as the ].<ref name="NASAExoplanetArchive"/> This situation is similar to that of some other planetary systems such as ], where different designations have been used for the same planets in the literature. | ||
| On 16 December 2022, two possible Earth-like ]s ] and ] were detected in the Kepler 138 system by the ] and ]s. | |||
| ==Stellar characteristics== | ==Stellar characteristics== | ||
| Kepler-138 is a ] with approximately |
Kepler-138 is a ] with approximately 54% the mass of and 54% the radius of the ].<ref name="Piaulet2022"/> It has a surface temperature of {{val|3726|44|40|ul=K}}.<ref name=Mann2017/> 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 |publisher=] |access-date=19 February 2011}}</ref> Kepler-138's ] (how bright it appears from Earth's perspective) is 13.04,<ref name="NASAExoplanetArchive"/> too dim to be seen with the naked eye. | ||
| ==Planetary system== | ==Planetary system== | ||
| The three inner known planets of Kepler-138 ] 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' orbital periods and relative diameters (compared to the host star) by monitoring each planet's transit of the star.<ref name = "Kipping"/><ref name = "Rowe"/> There is also a likely fourth non-transiting planet, Kepler-138e, detected through ]s.<ref name="Piaulet2022"/><ref name="NASA2022"/> | |||
| ⚫ | Although the innermost planet has a size similar to ], Kepler-138c and d both have a radius of about 1.5 ]<ref name="Piaulet2022"/> (revised from earlier estimates of 1.2 Earth radii).<ref name = "Kipping"/><ref name = "Rowe"/> Although Kepler-138c and d have similar radii, their masses and densities were initially thought to vary greatly. Of these two, the inner planet was thought to be consistent with a rocky ], whereas the outer planet's low density implies it may have a substantial proportion of water ice<ref name="Jontof-Hutter" /> or a significant gas envelope, resembling a miniaturized ] (a ]).<ref name = "Kipping"/> The striking differences between these two planets have been hypothesized to be due to ].<ref name = "Kipping"/> However, more recent observations as of 2022 have found similarly low densities for both planets c and d, suggesting that they are likely to be ]s.<ref name="Piaulet2022"/><ref name="NASA2022"/> The mass of candidate Kepler-138e would be intermediate of Mars and ]. While a radius could not be estimated for planet e, it is likely smaller than c and d and larger than b, which is consistent with an Earth-like composition.<ref name="Piaulet2022"/> | ||
| The three inner planets are too close to their star to be considered within the ],<ref name = "Briefing"/> while the likely planet Kepler-138e orbits near the inner edge of the habitable zone.<ref name="Piaulet2022"/> | |||
| ⚫ | Although the |
||
| {{OrbitboxPlanet begin | {{OrbitboxPlanet begin | ||
| | name = Kepler-138 | | name = Kepler-138 | ||
| | table_ref |
| table_ref = <ref name="Piaulet2022"/> | ||
| }} | }} | ||
| {{OrbitboxPlanet | {{OrbitboxPlanet | ||
| | exoplanet = |
| exoplanet = b | ||
| | mass_earth = 0. |
| mass_earth = {{val|0.07|0.02}} | ||
| | radius_earth = |
| radius_earth = {{val|0.64|0.02}} | ||
| | period = |
| period = {{val|10.3134|0.0003}} | ||
| | semimajor = 0. |
| semimajor = {{val|0.0753|0.0006}} | ||
| | eccentricity = 0. |
| eccentricity = {{val|0.020|0.009}} | ||
| | inclination = |
| inclination = {{val|88.67|0.08}} | ||
| }} | }} | ||
| {{OrbitboxPlanet | {{OrbitboxPlanet | ||
| | exoplanet = |
| exoplanet = c | ||
| | mass_earth = |
| mass_earth = {{val|2.3|0.6|0.5}} | ||
| | radius_earth = |
| radius_earth = {{val|1.51|0.04}} | ||
| | period = |
| period = {{val|13.78150|0.00007|0.00009}} | ||
| | semimajor = 0. |
| semimajor = {{val|0.0913|0.0007}} | ||
| | eccentricity = 0. |
| eccentricity = {{val|0.017|0.008|0.007}} | ||
| | inclination = |
| inclination = {{val|89.02|0.07}} | ||
| }} | }} | ||
| {{OrbitboxPlanet | {{OrbitboxPlanet | ||
| | exoplanet = |
| exoplanet = d | ||
| | mass_earth = 1. |
| mass_earth = {{val|2.1|0.6|0.7}} | ||
| | radius_earth = |
| radius_earth = {{val|1.51|0.04}} | ||
| | period = |
| period = {{val|23.0923|0.0006}} | ||
| | semimajor = 0. |
| semimajor = {{val|0.1288|0.0010}} | ||
| | eccentricity = 0. |
| eccentricity = {{val|0.010|0.005}} | ||
| | inclination = |
| inclination = {{val|89.04|0.04}} | ||
| }} | |||
| {{OrbitboxPlanet hypothetical | |||
| | exoplanet = e | |||
| | mass_earth = {{val|0.43|0.21|0.10}} | |||
| | radius_earth = | |||
| | period = {{val|38.230|0.006}} | |||
| | semimajor = {{val|0.1803|0.0014}} | |||
| | eccentricity = {{val|0.112|0.018|0.024}} | |||
| | inclination = {{val|88.53|1.0}} | |||
| }} | }} | ||
| {{Orbitbox end}} | {{Orbitbox end}} | ||
| The KOI and Kepler letters for these planets don't match. KOI-314.01 and KOI-314.02 were confirmed by Kipping et al.,<ref name="Kipping" /> but the Kepler team assigned the letters to ] and ] in their validation paper.<ref name="Rowe" /> | |||
| ==See also== | ==See also== | ||
| Line 123: | Line 139: | ||
| <ref name="GaiaDR3">{{Cite Gaia DR3|2102053446751282944}}</ref> | <ref name="GaiaDR3">{{Cite Gaia DR3|2102053446751282944}}</ref> | ||
| ⚫ | <ref name="kepler-catalogue">{{cite web|title=Kepler Input Catalog search result|publisher=]|url=http://archive.stsci.edu/kepler/kic10/search.php?kic_kepler_id=7603200&action=Search |access-date=4 March 2014}}</ref> | ||
| ⚫ | <ref name="Almenara2018">{{Cite journal|arxiv=1805.12520 |last1=Almenara |first1=J. M |display-authors=1 |title=Absolute densities in exoplanetary systems: Photodynamical modelling of Kepler-138 |journal=Monthly Notices of the Royal Astronomical Society |volume=478 |issue=1 |pages=460–486 |last2=Díaz |first2=R. F |last3=Dorn |first3=C |last4=Bonfils |first4=X |last5=Udry |first5=S |bibcode=2018MNRAS.478..460A |doi=10.1093/mnras/sty1050 |year=2018 |s2cid=54614204 }}</ref> | ||
| <ref name="NASAExoplanetArchive">{{cite web |url=https://exoplanetarchive.ipac.caltech.edu/overview/Kepler-138 |title=Kepler-138 |website=] |access-date=17 December 2022}}</ref> | |||
| <ref name="McQuillan2013">{{cite journal | title=Stellar Rotation Periods of The Kepler objects of Interest: A Dearth of Close-In Planets Around Fast Rotators | last1=McQuillan | first1=A. | last2=Mazeh | first2=T. | last3=Aigrain | first3=S. | journal=The Astrophysical Journal Letters | volume=775 | issue=1 | pages=L11 | year=2013 | arxiv=1308.1845 | bibcode=2013ApJ...775L..11M | doi=10.1088/2041-8205/775/1/L11 | s2cid=118557681 }}</ref> | <ref name="McQuillan2013">{{cite journal | title=Stellar Rotation Periods of The Kepler objects of Interest: A Dearth of Close-In Planets Around Fast Rotators | last1=McQuillan | first1=A. | last2=Mazeh | first2=T. | last3=Aigrain | first3=S. | journal=The Astrophysical Journal Letters | volume=775 | issue=1 | pages=L11 | year=2013 | arxiv=1308.1845 | bibcode=2013ApJ...775L..11M | doi=10.1088/2041-8205/775/1/L11 | s2cid=118557681 }}</ref> | ||
| <ref name = "Pineda">{{Cite journal | last1=Pineda | first1=Sebastian | 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| volume=767 | issue=1 | pages=28 | date=21 March 2013 | doi=10.1088/0004-637X/767/1/28 |arxiv = 1302.6231 |bibcode = 2013ApJ...767...28P | display-authors=etal | last2=Bottom | first2=Michael | s2cid=12541740 }}</ref> | |||
| <ref name = "Mann">{{Cite journal | last1=Mann | first1=Andrew | title=Spectro-thermometry of M Dwarfs and Their Candidate Planets: Too Hot, Too Cool, or Just Right? | journal=The Astrophysical Journal| volume=779 | issue=2 | pages=188 | date=4 December 2013 | doi=10.1088/0004-637X/779/2/188 |arxiv = 1311.0003 |bibcode = 2013ApJ...779..188M | display-authors=etal | last2=Gaidos | first2=Eric | hdl=2152/34640 | s2cid=119183731 }}</ref> | |||
| <ref name = "Kipping">{{Cite journal |last1=Kipping |first1=David |author-link=David Kipping |title=The Hunt for Exomoons with Kepler (HEK): IV. A Search for Moons around Eight M-Dwarfs |journal=The Astrophysical Journal |volume=784 |issue=1 |pages=28–41 |date=1 March 2014 |doi=10.1088/0004-637X/784/1/28 |arxiv=1401.1210 |bibcode=2014ApJ...784...28K |display-authors=2 |last2=Nesvorný |first2=D. |last3=Hartman |first3=J. |last4=Bakos |first4=G. Á. |last5=Schmitt |first5=A. R.|s2cid=119305398 }}</ref> | |||
| <ref name="Rowe">{{cite journal |title=Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems |date=2014 |last1= Rowe |first1=Jason F. | arxiv=1402.6534 |display-authors=etal |doi=10.1088/0004-637X/784/1/45 |volume=784 |issue=1 |journal=The Astrophysical Journal |page=45 |bibcode=2014ApJ...784...45R|s2cid=119118620 }}</ref> | |||
| <ref name = "Jontof-Hutter">{{cite journal |last1=Jontof-Hutter |first1=D |title=Mass of the Mars-sized Exoplanet Kepler-138b from Transit Timing |journal=Nature |volume=522 |issue=7556 |pages=321–323 |date=18 June 2015 |doi=10.1038/nature14494 |arxiv=1506.07067 |bibcode=2015Natur.522..321J |display-authors=etal |last2=Rowe |first2=J |pmid=26085271|s2cid=205243944 }}</ref> | |||
| ⚫ | <ref name=Mann2017>{{citation|arxiv=1705.01545|title=THE GOLD STANDARD: ACCURATE STELLAR AND PLANETARY PARAMETERS FOR EIGHT Kepler M DWARF SYSTEMS ENABLED BY PARALLAXES|year=2017|doi=10.3847/1538-3881/aa7140|last1=Mann|first1=Andrew W.|last2=Dupuy|first2=Trent|last3=Muirhead|first3=Philip S.|last4=Johnson|first4=Marshall C.|last5=Liu|first5=Michael C.|last6=Ansdell|first6=Megan|last7=Dalba|first7=Paul A.|last8=Swift|first8=Jonathan J.|last9=Hadden|first9=Sam|journal=The Astronomical Journal|volume=153|issue=6|page=267|bibcode=2017AJ....153..267M|s2cid=119325474 |doi-access=free }}</ref> | ||
| ⚫ | <!--<ref name="Almenara2018">{{Cite journal|arxiv=1805.12520 |last1=Almenara |first1=J. M |display-authors=1 |title=Absolute densities in exoplanetary systems: Photodynamical modelling of Kepler-138 |journal=Monthly Notices of the Royal Astronomical Society |volume=478 |issue=1 |pages=460–486 |last2=Díaz |first2=R. F |last3=Dorn |first3=C |last4=Bonfils |first4=X |last5=Udry |first5=S |bibcode=2018MNRAS.478..460A |doi=10.1093/mnras/sty1050 |year=2018 |s2cid=54614204 }}</ref>--> | ||
| <ref name="Piaulet2022">{{cite journal |last1=Piaulet |first1=Caroline |last2=Benneke |first2=Björn |display-authors=etal |date=15 December 2022 |title=Evidence for the volatile-rich composition of a 1.5-Earth-radius planet |journal=] |volume= 7|issue= |page=206 |doi=10.1038/s41550-022-01835-4 |arxiv=2212.08477|bibcode=2023NatAs...7..206P |s2cid=254764810 }}</ref> | |||
| <ref name="NASA2022">{{cite web |url=https://exoplanets.nasa.gov/news/1717/two-super-earths-may-be-mostly-water/ |title=Two Super-Earths May Be Mostly Water |date=15 December 2022 |publisher=] |access-date=17 December 2022}}</ref> | |||
| }} | }} | ||
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Latest revision as of 03:27, 31 August 2024
Red dwarf in the constellation Lyra
.png) Artist's impression of the planets orbiting Kepler-138 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19 21 31.56798 |
| Declination | +43° 17′ 34.6810″ |
| Apparent magnitude (V) | 13.040±0.092 |
| Characteristics | |
| Spectral type | M1V |
| Apparent magnitude (V) | 13.040±0.092 |
| Apparent magnitude (Kepler) | 12.925 |
| Astrometry | |
| Radial velocity (Rv) | −37.25±0.72 km/s |
| Proper motion (μ) | RA: −20.461±0.012 mas/yr Dec.: 22.641±0.012 mas/yr |
| Parallax (π) | 14.9019 ± 0.0097 mas |
| Distance | 218.9 ± 0.1 ly (67.11 ± 0.04 pc) |
| Absolute magnitude (MV) | 8.81 ± 0.28 |
| Details | |
| Mass | 0.535±0.012 M☉ |
| Radius | 0.535+0.013 −0.014 R☉ |
| Luminosity (bolometric) | 0.056±0.004 L☉ |
| Luminosity (visual, LV) | 0.026 ± 0.006 L☉ |
| Surface gravity (log g) | 4.71±0.03 cgs |
| Temperature | 3726+44 −40 K |
| Metallicity | -0.28 ± 0.10 dex |
| Rotation | 19.394±0.013 days |
| Rotational velocity (v sin i) | ~3 km/s |
| Age | >1 Gyr |
| Other designations | |
| Kepler-138, KOI-314, KIC 7603200, TIC 159376971, 2MASS J19213157+4317347 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
| KIC | data |
Kepler-138, also known as KOI-314, is a red dwarf located in the constellation Lyra, 219 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 transiting their stars.
The star hosts three confirmed planets and a likely fourth, including the lowest-mass exoplanet with a measured mass and size discovered to date, Kepler-138b, with a mass comparable to that of Mars. Kepler-138d is remarkable for its low density; initially thought likely to be a gas dwarf, more recent observations as of 2022 show that it, as well as planet c, are likely to be ocean worlds.
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.
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 phenomena 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 who referred to the star as KOI-314, as the Kepler designation had not been assigned yet.
Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations ".01", ".02", ".03", etc. after the star's name, in the order of discovery. If planet 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, 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 in the system.
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. These designations have been used by subsequent studies, and by databases such as the NASA Exoplanet Archive. This situation is similar to that of some other planetary systems such as Mu Arae, where different designations have been used for the same planets in the literature.
On 16 December 2022, two possible Earth-like water worlds Kepler-138 c and Kepler-138 d were detected in the Kepler 138 system by the Hubble and Spitzer Space Telescopes.
Stellar characteristics
Kepler-138 is a red dwarf with approximately 54% the mass of and 54% the radius of the Sun. It has a surface temperature of 3726+44
−40 K. In comparison, the Sun has a surface temperature of 5778 K. Kepler-138's apparent magnitude (how bright it appears from Earth's perspective) is 13.04, too dim to be seen with the naked eye.
Planetary system
The three inner known planets of Kepler-138 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' orbital periods and relative diameters (compared to the host star) by monitoring each planet's transit of the star. There is also a likely fourth non-transiting planet, Kepler-138e, detected through transit-timing variations.
Although the innermost planet has a size similar to Mars, Kepler-138c and d both have a radius of about 1.5 Earth radii (revised from earlier estimates of 1.2 Earth radii). Although Kepler-138c and d have similar radii, their masses and densities were initially thought to vary greatly. Of these two, the inner planet was thought to be consistent with a rocky super-Earth, whereas the outer planet's low density implies it may have a substantial proportion of water ice or a significant gas envelope, resembling a miniaturized gas giant (a gas dwarf). The striking differences between these two planets have been hypothesized to be due to photoevaporation. However, more recent observations as of 2022 have found similarly low densities for both planets c and d, suggesting that they are likely to be ocean worlds. The mass of candidate Kepler-138e would be intermediate of Mars and Venus. While a radius could not be estimated for planet e, it is likely smaller than c and d and larger than b, which is consistent with an Earth-like composition.
The three inner planets are too close to their star to be considered within the habitable zone, while the likely planet Kepler-138e orbits near the inner edge of the habitable zone.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 0.07±0.02 M🜨 | 0.0753±0.0006 | 10.3134±0.0003 | 0.020±0.009 | 88.67±0.08° | 0.64±0.02 R🜨 |
| c | 2.3+0.6 −0.5 M🜨 |
0.0913±0.0007 | 13.78150+0.00007 −0.00009 |
0.017+0.008 −0.007 |
89.02±0.07° | 1.51±0.04 R🜨 |
| d | 2.1+0.6 −0.7 M🜨 |
0.1288±0.0010 | 23.0923±0.0006 | 0.010±0.005 | 89.04±0.04° | 1.51±0.04 R🜨 |
| e (unconfirmed) | 0.43+0.21 −0.10 M🜨 |
0.1803±0.0014 | 38.230±0.006 | 0.112+0.018 −0.024 |
88.53±1.0° | — |
See also
References
- ^ 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.
- ^ "Kepler-138". NASA Exoplanet Archive. Retrieved 17 December 2022.
- ^ Pineda, Sebastian; Bottom, Michael; et al. (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. 767 (1): 28. arXiv:1302.6231. Bibcode:2013ApJ...767...28P. doi:10.1088/0004-637X/767/1/28. S2CID 12541740.
- ^ "Kepler Input Catalog search result". Space Telescope Science Institute. Retrieved 4 March 2014.
- ^ Piaulet, Caroline; Benneke, Björn; et al. (15 December 2022). "Evidence for the volatile-rich composition of a 1.5-Earth-radius planet". Nature Astronomy. 7: 206. arXiv:2212.08477. Bibcode:2023NatAs...7..206P. doi:10.1038/s41550-022-01835-4. S2CID 254764810.
- ^ Mann, Andrew W.; Dupuy, Trent; Muirhead, Philip S.; Johnson, Marshall C.; Liu, Michael C.; Ansdell, Megan; Dalba, Paul A.; Swift, Jonathan J.; Hadden, Sam (2017), "THE GOLD STANDARD: ACCURATE STELLAR AND PLANETARY PARAMETERS FOR EIGHT Kepler M DWARF SYSTEMS ENABLED BY PARALLAXES", The Astronomical Journal, 153 (6): 267, arXiv:1705.01545, Bibcode:2017AJ....153..267M, doi:10.3847/1538-3881/aa7140, S2CID 119325474
- McQuillan, A.; Mazeh, T.; Aigrain, S. (2013). "Stellar Rotation Periods of The Kepler objects of Interest: A Dearth of Close-In Planets Around Fast Rotators". The Astrophysical Journal Letters. 775 (1): L11. arXiv:1308.1845. Bibcode:2013ApJ...775L..11M. doi:10.1088/2041-8205/775/1/L11. S2CID 118557681.
- ^ Kipping, David; Nesvorný, D.; et al. (1 March 2014). "The Hunt for Exomoons with Kepler (HEK): IV. A Search for Moons around Eight M-Dwarfs". The Astrophysical Journal. 784 (1): 28–41. arXiv:1401.1210. Bibcode:2014ApJ...784...28K. doi:10.1088/0004-637X/784/1/28. S2CID 119305398.
- "Kepler-138". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 17 December 2022.
- Mann, Andrew; Gaidos, Eric; et al. (4 December 2013). "Spectro-thermometry of M Dwarfs and Their Candidate Planets: Too Hot, Too Cool, or Just Right?". The Astrophysical Journal. 779 (2): 188. arXiv:1311.0003. Bibcode:2013ApJ...779..188M. doi:10.1088/0004-637X/779/2/188. hdl:2152/34640. S2CID 119183731.
- ^ Jontof-Hutter, D; Rowe, J; et al. (18 June 2015). "Mass of the Mars-sized Exoplanet Kepler-138b from Transit Timing". Nature. 522 (7556): 321–323. arXiv:1506.07067. Bibcode:2015Natur.522..321J. doi:10.1038/nature14494. PMID 26085271. S2CID 205243944.
- ^ "Two Super-Earths May Be Mostly Water". NASA. 15 December 2022. Retrieved 17 December 2022.
- Timmer, John (15 December 2022). "Scientists may have found the first water worlds". Ars Technica. Retrieved 17 December 2022.
- Morton, Timothy; Johnson, John (23 August 2011). "On the Low False Positive Probabilities of Kepler Planet Candidates". The Astrophysical Journal. 738 (2): 170. arXiv:1101.5630. Bibcode:2011ApJ...738..170M. doi:10.1088/0004-637X/738/2/170. S2CID 35223956.
- "Working Group on Extrasolar Planets: Definition of a "Planet"". IAU position statement. 28 February 2003. Archived from the original on 16 September 2006. Retrieved 9 September 2006.
- NASA (27 January 2014). "Kepler – Discoveries – Summary Table". NASA. Archived from the original on 27 May 2010. Retrieved 1 March 2014.
- ^ David Kipping (26 January 2014). "David Kipping - Press Briefing on First Earth-Mass Transiting Planet, KOI-314c". YouTube. Retrieved 1 March 2014.
- ^ Borucki, William J.; Koch, David G.; Batalha, Natalie; Brown, Timothy M.; Bryson, Stephen T.; Caldwell, Douglas; Christensen-Dalsgaard, Jørgen; Cochran, William D.; Devore, Edna; Dunham, Edward W.; Gautier, Thomas N.; Geary, John C.; Gilliland, Ronald; Gould, Alan; Howell, Steve B.; Jenkins, Jon M.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Rowe, Jason; Sasselov, Dimitar; Boss, Alan; Charbonneau, David; Ciardi, David; Doyle, Laurance; Dupree, Andrea K.; Ford, Eric B.; Fortney, Jonathan; Holman, Matthew J.; et al. (29 June 2011). "Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data". The Astrophysical Journal. 736 (1): 19. arXiv:1102.0541. Bibcode:2011ApJ...736...19B. doi:10.1088/0004-637X/736/1/19. S2CID 15233153.
- Batalha, Natalie; Rowe, Jason F.; Barclay, Thomas; Burke, Christopher J.; Caldwell, Douglas A.; Christiansen, Jessie L.; Mullally, Fergal; Thompson, Susan E.; Brown, Timothy M.; Dupree, Andrea K.; Fabrycky, Daniel C.; Ford, Eric B.; Fortney, Jonathan J.; Gilliland, Ronald L.; Isaacson, Howard; Latham, David W.; Marcy, Geoffrey W.; Quinn, Samuel N.; Ragozzine, Darin; Shporer, Avi; Borucki, William J.; Ciardi, David R.; Gautier, Thomas N.; Haas, Michael R.; Jenkins, Jon M.; Koch, David G.; Lissauer, Jack J.; Rapin, William; Basri, Gibor S.; et al. (5 February 2013). "Planetary Candidates Observed by Kepler. III. Analysis of the First 16 Months of Data". The Astrophysical Journal Supplement. 204 (2): 24. arXiv:1202.5852. Bibcode:2013ApJS..204...24B. doi:10.1088/0067-0049/204/2/24. S2CID 19023502.
- ^ 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 .
- ^ Rowe, Jason F.; et al. (2014). "Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems". The Astrophysical Journal. 784 (1): 45. arXiv:1402.6534. Bibcode:2014ApJ...784...45R. doi:10.1088/0004-637X/784/1/45. S2CID 119118620.
- Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
External links
- The Hunt for Exomoons with Kepler (HEK) project - HEK.
- Kepler Mission – NASA.
- Kepler – Discoveries – Summary Table – NASA.
- Kepler – Tally of Planets/interactive (2013) – NYT.
- Video (10:47) - David Kipping - Press Briefing on First Earth-Mass Transiting Planet, KOI-314c (01/06/2014).
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