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| name = Kepler-444 | name = Kepler-444
}} }}
{{Starbox observe {{Starbox image
| image = ]
| caption = Adaptive optics image of the Kepler-444 system from Zhang et al.<ref name=Zhang2023/>
}}
{{Starbox observe 2s
| epoch = J2000 | epoch = J2000
| equinox = 2000 | equinox = 2000
| constell = ] | constell = ]<ref name="Campante2015"/>
| component1 = Kepler-444 A
⚫ | ra = {{RA|19|19|00.5489}}<ref name="Gaia DR3"/>
| dec = {{DEC|+41|38|04.582}}<ref name="Gaia DR3"/> | ra1 = {{RA|19|19|00.5489}}<ref name="Gaia DR3 for A"/>
| appmag_v = 8.86<ref name=ducati2002/> | dec1 = {{DEC|+41|38|04.582}}<ref name="Gaia DR3 for A"/>
| appmag_v1 = 8.86<ref name=ducati2002/>
| component2 = Kepler-444 B/C
⚫ | ra2 = {{RA|19|19|00.3922}}<ref name="Gaia DR3 for B/C"/>
| dec2 = {{DEC|+41|38|04.013}}<ref name="Gaia DR3 for B/C"/>
| appmag_v2 =
}} }}
{{Starbox character {{Starbox character
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}} }}
{{Starbox astrometry {{Starbox astrometry
| component1 = Kepler-444 A
| radial_v = {{val|-123.05|0.17}}<ref name="Dupuy2016"/> | radial_v = {{val|-123.05|0.17}}<ref name="Dupuy2016"/>
| prop_mo_ra = {{val|94.639|(13)}} | prop_mo_ra = {{val|94.639|(13)}}
| prop_mo_dec = {{val|−632.269|(14)}} | prop_mo_dec = {{val|−632.269|(14)}}
| pm_footnote = <ref name="Gaia DR3"/> | pm_footnote = <ref name="Gaia DR3 for A"/>
| parallax = 27.3578 | parallax = 27.3578
| p_error = 0.0125 | p_error = 0.0125
| parallax_footnote = <ref name="Gaia DR3"/> | parallax_footnote = <ref name="Gaia DR3 for A"/>
| absmag_v = | absmag_v =
| component2 = Kepler-444 B/C
| radial_v2 =
| prop_mo_ra2 = {{val|94.508|(55)}}
| prop_mo_dec2 = {{val|−630.781|(78)}}
| pm_footnote2 = <ref name="Gaia DR3 for B/C"/>
| parallax2 = 27.6079
| p_error2 = 0.0545
| parallax_footnote2 = <ref name="Gaia DR3 for B/C"/>
| absmag_v2 =
}} }}
{{Starbox orbit {{Starbox orbit
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}} }}
{{Starbox reference {{Starbox reference
| Simbad = KOI-3158 | Simbad = BD%2B41+3306
| Simbad2 = KOI+3158B |sn2=B/C | Simbad2 = BD%2B41+3306B |sn2=B/C
| NSTED = Kepler-444
}} }}
{{Starbox end}} {{Starbox end}}


'''Kepler-444''' (or '''KOI-3158''', '''KIC 6278762''', '''2MASS J19190052+4138043''', '''BD+41°3306''')<ref name="Simbad for A"/> is a ], estimated to be 11.2 billion years old (more than 80% of the age of the ]),<ref name="SP-20150127" /> approximately {{convert|119|ly|pc}} away from ] in the ] ]. On 27 January 2015, the ] is reported to have confirmed the detection of five sub-Earth-sized ] ] orbiting the main star. The star is a ].<ref name="NASA-20150128"/><ref name="AP-20150127"/><ref name="UT-20150127"/><ref name="SP-20150127"/><ref name="EX-20150127"/> All of the planets are far too close to their star to harbour life forms.<ref name="NASA-20150128" /> '''Kepler-444''' (or '''KOI-3158''', '''KIC 6278762''', '''2MASS J19190052+4138043''', '''BD+41°3306''')<ref name="Simbad for A"/> is a ], estimated to be 11.2 billion years old (more than 80% of the age of the ]),<ref name="SP-20150127" /> approximately {{convert|119|ly|pc}} away from ] in the ] ]. On 27 January 2015, the ] is reported to have confirmed the detection of five sub-Earth-sized ] ] orbiting the main star. The star is a ].<ref name="NASA-20150128"/><ref name="AP-20150127"/><ref name="UT-20150127"/><ref name="SP-20150127"/> All of the planets are far too close to their star to harbour life forms.<ref name="NASA-20150128" />


==Discovery== ==Discovery==
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The star, Kepler-444, is approximately 11.2 billion years old, whereas the ] is only 4.6 billion years old. The age is that of Kepler-444 A, an ] of spectral type K0.<ref name="SL-20140128"/> Despite this great age, it is in middle of its main-sequence lifespan, much like the Sun. The star, Kepler-444, is approximately 11.2 billion years old, whereas the ] is only 4.6 billion years old. The age is that of Kepler-444 A, an ] of spectral type K0.<ref name="SL-20140128"/> Despite this great age, it is in middle of its main-sequence lifespan, much like the Sun.


The original research on Kepler-444 was published in '']'' on 27 January 2015 under the title "An ancient extrasolar system with five sub-Earth-size planets" by a team of 40 authors, the abstract reads as follows:<ref name="Campante2015"/> The original research on Kepler-444 was published in '']'' on 27 January 2015 under the title "An ancient extrasolar system with five sub-Earth-size planets" by a team of 40 authors.<ref name="Campante2015"/>

<blockquote>The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of ], which tend to be ]. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the Universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the ] and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planet system orbiting the target star and provide a detailed characterization of its planetary and orbital parameters based on an analysis of the ]. Kepler-444 is the densest star with detected solar-like oscillations. We use ] to directly measure a precise age of 11.2+/-1.0 Gyr for the host star, indicating that Kepler-444 formed when the Universe was less than 20% of its current age and making it the oldest known system of ]. We thus show that Earth-size planets have formed throughout most of the Universe's 13.8-billion-year history, leaving open the possibility for the existence of ancient life in the ]. The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of ]." The star is believed to have 2 M dwarfs in orbit around it with the fainter companion 1.8 arc-seconds from the main star.
</blockquote>


==Stellar system== ==Stellar system==
]
The Kepler-444 system consists of the planet hosting primary and a pair of M-dwarf stars. The M-dwarfs orbit each other at a distance of less than 0.3 ] while the pair orbits the primary in a highly ] 324-year orbit. The pair comes within 23.55 AU of the primary potentially truncating the protoplanetary disk from which the planets formed at 8 AU. This would have depleted the availability of solid material to form the observed planets.<ref name="Zhang2023"/> The Kepler-444 system consists of the planet hosting primary and a pair of M-dwarf stars. The M-dwarfs orbit each other at a distance of less than 0.3 ] while the pair orbits the primary in a highly ] 324-year orbit. The pair comes within 23.55 AU of the primary potentially truncating the protoplanetary disk from which the planets formed at 8 AU. This would have depleted the availability of solid material to form the observed planets.<ref name="Zhang2023"/>


Previous stellar orbit solution was ever more extreme, period was shorter (211 years) and eccentricity was much larger (e=0.865), moving periastron to 5 AU, severely reducing the estimated protoplanetary disk size to 1–2 AU and its estimated mass from ~600 to ~4 Earth masses.<ref name="Dupuy2016"/> Previous stellar orbit solution was ever more extreme, period was shorter (211 years) and eccentricity was much larger (e=0.865), moving periastron to 5 AU, severely reducing the estimated protoplanetary disk size to 1–2 AU and its estimated mass from ~600 to ~4 Earth masses.<ref name="Dupuy2016"/>

] measurements of Kepler-444 show a linear trend, which aligns well with the orbit outlined by Dupuy et al. (see diagram above)<ref name="Weiss2024"/>


==Planetary system== ==Planetary system==
All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed,<ref name="EX-20150127" /> smaller than the size of ] (but bigger than ]) and each of the exoplanets completes an orbit around the host star in less than 10 days.<ref name="NASA-20150128" /><ref name="SP-20150127" /> Thus, the planetary system is very compact, as even the furthest known planet, Kepler-444f, still orbits closer to the star than Mercury is to the ].<ref name="SL-20140128" /> According to NASA, no life as we know it could exist on these hot exoplanets, due to their close orbital distances to the host star.<ref name="NASA-20150128" /> To keep the known planetary system stable, no additional giant planets can be located within 5.5 ] of the parent star.<ref>{{citation|arxiv=1702.07714|title=Effects of Unseen Additional Planetary Perturbers on Compact Extrasolar Planetary Systems|year=2017|doi=10.1093/mnras/stx461|last1=Becker|first1=Juliette C.|last2=Adams|first2=Fred C.|journal=Monthly Notices of the Royal Astronomical Society|volume=468|issue=1|pages=549–563|bibcode=2017MNRAS.468..549B|s2cid=119325005}}</ref> All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed, smaller than the size of ] (but bigger than ]) and each of the exoplanets completes an orbit around the host star in less than 10 days.<ref name="NASA-20150128" /><ref name="SP-20150127" /> Thus, the planetary system is very compact, as even the furthest known planet, Kepler-444f, still orbits closer to the star than Mercury is to the ].<ref name="SL-20140128" /> According to NASA, no life as we know it could exist on these hot exoplanets, due to their close orbital distances to the host star.<ref name="NASA-20150128" /> To keep the known planetary system stable, no additional giant planets can be located within 5.5 ] of the parent star.<ref>{{citation|arxiv=1702.07714|title=Effects of Unseen Additional Planetary Perturbers on Compact Extrasolar Planetary Systems|year=2017|doi=10.1093/mnras/stx461|last1=Becker|first1=Juliette C.|last2=Adams|first2=Fred C.|journal=Monthly Notices of the Royal Astronomical Society|volume=468|issue=1|pages=549–563|doi-access=free |bibcode=2017MNRAS.468..549B|s2cid=119325005}}</ref>


Moreover, the system is pervaded by high-order resonance chain: period ratios are 4:5, 3:4, 4:5, 4:5. This tight chain is unperturbed and very likely continues farther from Kepler-444A. Moreover, the system is pervaded by high-order resonance chain: period ratios are 4:5, 3:4, 4:5, 4:5. This tight chain is unperturbed and very likely continues farther from Kepler-444A.

A marginally significant peak appears at 72 days in the radial velocity data when the linear trend attributed to the stellar companions is subtracted. However, this signal suggests an ] that is unphysically high, leading to orbits that would intersect the known planets. The signal likely stems from complexities within the long-term radial velocity signal of the Kepler-444 ABC system and may also be associated with the orbit of the BC pair.<ref name="Weiss2024"/>

{{OrbitboxPlanet begin {{OrbitboxPlanet begin
| table_ref = <ref name="EX-20150127" /><ref name="Mills2017"/> | table_ref = <ref name="Campante2015" /><ref name="Mills2017"/>{{efn|The eccentricity has a non-Gaussian posterior distribution and so the median is an overestimate of the true eccentricity.<ref name="Campante2015" />}}
}} }}
{{OrbitboxPlanet {{OrbitboxPlanet
| exoplanet = b | exoplanet = b
| mass_earth = | mass_earth = <0.079
| semimajor = 0.04178 | semimajor = {{val|0.04178|0.00079}}
| period = {{val|3.600105|0.000031|0.000037}} | period = {{val|3.6001053|0.0000083|0.0000080}}
| eccentricity = 0.16 | eccentricity = {{val|0.16|0.21|0.10}}
| inclination = 88 | inclination = {{val|88.0|1.2|0.6}}
| radius_earth = 0.406{{±|0.013}} | radius_earth = {{val|0.406|0.013|0.013}}
}} }}
{{OrbitboxPlanet {{OrbitboxPlanet
| exoplanet = c | exoplanet = c
| mass_earth = | mass_earth = <0.16
| semimajor = 0.04881 | semimajor = {{val|0.04881|0.00093}}
| period = 4.545876{{±|0.000031}} | period = {{val|4.5458841|0.0000070|0.0000071}}
| eccentricity = 0.31 | eccentricity = {{val|0.31|0.12|0.15}}
| inclination = 88.2 | inclination = {{val|88.2|1.2|1.0}}
| radius_earth = 0.521{{±|0.017}} | radius_earth = {{val|0.521|0.017|0.016}}
}} }}
{{OrbitboxPlanet {{OrbitboxPlanet
| exoplanet = d | exoplanet = d
| mass_earth = {{val|0.036|0.065|0.020}} | mass_earth = {{val|0.036|0.065|0.020}}
| semimajor = 0.06 | semimajor = {{val|0.0600|0.0011}}
| period = {{val|6.189437|0.000053|0.000037}} | period = {{val|6.189392|0.000012|0.000012}}
| eccentricity = 0.18 | eccentricity = {{val|0.18|0.16|0.12}}
| inclination = 88.16 | inclination = {{val|88.16|0.81|0.55}}
| radius_earth = 0.54{{±|0.017}} | radius_earth = {{val|0.540|0.017|0.016}}
}} }}
{{OrbitboxPlanet {{OrbitboxPlanet
| exoplanet = e | exoplanet = e
| mass_earth = {{val|0.034|0.059|0.019}} | mass_earth = {{val|0.034|0.059|0.019}}
| semimajor = 0.0696 | semimajor = {{val|0.0696|0.0013}}
| period = {{val|7.743467|0.00006|0.0001}} | period = {{val|7.743493|0.000017|0.000016}}
| eccentricity = 0.1 | eccentricity = {{val|0.10|0.20|0.07}}
| inclination = 89.13 | inclination = {{val|89.13|0.54|0.52}}
| radius_earth = {{val|0.555|0.018|0.016}} | radius_earth = {{val|0.555|0.018|0.016}}
}} }}
{{OrbitboxPlanet {{OrbitboxPlanet
| exoplanet = f | exoplanet = f
| mass_earth = | mass_earth = <0.22
| semimajor = 0.0811 | semimajor = {{val|0.0811|0.0015}}
| period = {{val|9.740501|0.000078|0.000026}} | period = {{val|9.740486|0.000013|0.000013}}
| eccentricity = 0.29 | eccentricity = {{val|0.29|0.20|0.19}}
| inclination = 87.96 | inclination = {{val|87.96|0.36|0.31}}
| radius_earth = 0.767{{±|0.025}} | radius_earth = {{val|0.767|0.025|0.024}}
}} }}
{{Orbitbox end}} {{Orbitbox end}}
<!---
{{wide image|LombergA1024.jpg|600px|align-cap=center|The '']'' search volume, in the context of the ].}}
--->
{{-}} {{-}}


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* ] * ]
* ] - an ancient planetary system in ] * ] - an ancient planetary system in ]

==Notes==
{{notelist}}


==References== ==References==
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<ref name="Dupuy2016">{{cite journal | title=Orbital Architectures of Planet-Hosting Binaries. I. Forming Five Small Planets in the Truncated Disk of Kepler-444A | last1=Dupuy | first1=Trent J. | last2=Kratter | first2=Kaitlin M. | last3=Kraus | first3=Adam L. | last4=Isaacson | first4=Howard | last5=Mann | first5=Andrew W. | last6=Ireland | first6=Michael J. | last7=Howard | first7=Andrew W. | last8=Huber | first8=Daniel | display-authors=1 | journal=The Astrophysical Journal | volume=817 | issue=1 | article-number=80 | page=<!-- to prevent citation bot adding nonexistent page number--> | year=2016 | arxiv=1512.03428 | bibcode=2016ApJ...817...80D | bibcode-access=free | doi=10.3847/0004-637X/817/1/80 | doi-access=free }}</ref> <ref name="Dupuy2016">{{cite journal | title=Orbital Architectures of Planet-Hosting Binaries. I. Forming Five Small Planets in the Truncated Disk of Kepler-444A | last1=Dupuy | first1=Trent J. | last2=Kratter | first2=Kaitlin M. | last3=Kraus | first3=Adam L. | last4=Isaacson | first4=Howard | last5=Mann | first5=Andrew W. | last6=Ireland | first6=Michael J. | last7=Howard | first7=Andrew W. | last8=Huber | first8=Daniel | display-authors=1 | journal=The Astrophysical Journal | volume=817 | issue=1 | article-number=80 | page=<!-- to prevent citation bot adding nonexistent page number--> | year=2016 | arxiv=1512.03428 | bibcode=2016ApJ...817...80D | bibcode-access=free | doi=10.3847/0004-637X/817/1/80 | doi-access=free }}</ref>


<ref name="Gaia DR3">{{Cite Gaia DR2|2101486923385239808}}</ref> <ref name="Gaia DR3 for A">{{Cite Gaia DR3|2101486923385239808}}</ref>

<ref name="Gaia DR3 for B/C">{{Cite Gaia DR3|2101486923382009472}}</ref>


<ref name="Mazeh2015">{{cite journal | title=Photometric Amplitude Distribution of Stellar Rotation of KOIs—Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars | last1=Mazeh | first1=Tsevi | last2=Perets | first2=Hagai B. | last3=McQuillan | first3=Amy | last4=Goldstein | first4=Eyal S. | display-authors=1 | journal=The Astrophysical Journal | volume=801 | issue=1 | at=3 | year=2015 | arxiv=1501.01288 | bibcode=2015ApJ...801....3M | bibcode-access=free | doi=10.1088/0004-637X/801/1/3 | doi-access=free }}</ref> <ref name="Mazeh2015">{{cite journal | title=Photometric Amplitude Distribution of Stellar Rotation of KOIs—Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars | last1=Mazeh | first1=Tsevi | last2=Perets | first2=Hagai B. | last3=McQuillan | first3=Amy | last4=Goldstein | first4=Eyal S. | display-authors=1 | journal=The Astrophysical Journal | volume=801 | issue=1 | at=3 | year=2015 | arxiv=1501.01288 | bibcode=2015ApJ...801....3M | bibcode-access=free | doi=10.1088/0004-637X/801/1/3 | doi-access=free }}</ref>


<ref name="Mills2017">{{cite journal | title=Mass, Density, and Formation Constraints in the Compact, Sub-Earth Kepler-444 System including Two Mars-mass Planets | last1=Mills | first1=Sean M. | last2=Fabrycky | first2=Daniel C. | journal=The Astrophysical Journal Letters | volume=838 | issue=1 | at=L11 | year=2017 | arxiv=1703.03417 | bibcode=2017ApJ...838L..11M | bibcode-access=free | doi=10.3847/2041-8213/aa6543 | doi-access=free }}</ref> <ref name="Mills2017">{{cite journal | title=Mass, Density, and Formation Constraints in the Compact, Sub-Earth Kepler-444 System including Two Mars-mass Planets | last1=Mills | first1=Sean M. | last2=Fabrycky | first2=Daniel C. | journal=The Astrophysical Journal Letters | volume=838 | issue=1 | article-number=L11 | page=<!-- to prevent citation bot adding nonexistent page number--> | year=2017 | arxiv=1703.03417 | bibcode=2017ApJ...838L..11M | bibcode-access=free | doi=10.3847/2041-8213/aa6543 | doi-access=free }}</ref>


<ref name="Simbad for A">{{cite simbad | title=BD+41 3306 | access-date=2020-08-20 }}</ref> <ref name="Simbad for A">{{cite simbad | title=BD+41 3306 | access-date=2020-08-20 }}</ref>
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<ref name="Simbad for B">{{cite simbad | title=BD+41 3306B | access-date=2020-08-20 }}</ref> <ref name="Simbad for B">{{cite simbad | title=BD+41 3306B | access-date=2020-08-20 }}</ref>


<ref name="NASA-20150128">{{cite web |last=Johnson |first=Michele |title=Astronomers Discover Ancient System with Five Small Planets |url=http://www.nasa.gov/ames/kepler/astronomers-discover-ancient-system-with-five-small-planets |date=28 January 2015 |work=] |access-date=29 January 2015}}</ref> <ref name="NASA-20150128">{{cite web |last=Johnson |first=Michele |title=Astronomers Discover Ancient System with Five Small Planets |url=https://www.jpl.nasa.gov/news/astronomers-discover-ancient-system-with-five-small-planets |date=28 January 2015 |work=] |access-date=29 January 2015}}</ref>


<ref name="AP-20150127">{{cite news |last=Dunn |first=Marcia |title=Astronomers find solar system more than double ours in age |url=http://apnews.excite.com/article/20150127/us-sci--old_solar_system-56b7594709.html |date=27 January 2015 |work=] |access-date=27 January 2015}}</ref> <ref name="AP-20150127">{{cite news |last=Dunn |first=Marcia |title=Astronomers find solar system more than double ours in age |url=https://apnews.com/general-news-1b42cd9c22fa48a6b57fcbe1dccbd617 |date=27 January 2015 |work=] |access-date=27 January 2015}}</ref>


<ref name="UT-20150127">{{cite web |last1=Atkinson |first1=Nancy |title=Oldest Planetary System Discovered, Improving the Chances for Intelligent Life Everywhere |url=http://www.universetoday.com/118510/oldest-planetary-system-discovered-improving-the-chances-for-intelligent-life-everywhere/ |date=27 January 2015 |work=] |access-date=27 January 2015}}</ref> <ref name="UT-20150127">{{cite web |last1=Atkinson |first1=Nancy |title=Oldest Planetary System Discovered, Improving the Chances for Intelligent Life Everywhere |url=http://www.universetoday.com/118510/oldest-planetary-system-discovered-improving-the-chances-for-intelligent-life-everywhere/ |date=27 January 2015 |work=] |access-date=27 January 2015}}</ref>


<ref name="SP-20150127">{{cite web |last=Wall |first=Mike |title=Found! 5 Ancient Alien Planets Nearly As Old As the Universe |url=http://www.space.com/28386-ancient-alien-planets-discovery-kepler-444.html |date=27 January 2015 |work=] |access-date=27 January 2015}}</ref> <ref name="SP-20150127">{{cite web |last=Wall |first=Mike |title=Found! 5 Ancient Alien Planets Nearly As Old As the Universe |url=http://www.space.com/28386-ancient-alien-planets-discovery-kepler-444.html |date=27 January 2015 |work=] |access-date=27 January 2015}}</ref>

<ref name="EX-20150127">{{cite encyclopedia |author=Staff |title=Exoplanet Catalog |url=https://exoplanet.eu/catalog/ |date=27 January 2015 |encyclopedia=] |access-date=27 January 2015}}</ref>


<ref name="CAL-201311">{{cite web |author=Staff |title=Second Kepler Science Conference - NASA Ames Research Center, Mountain View, CA - Nov. 4-8, 2013 - Agenda |url=http://nexsci.caltech.edu/conferences/KeplerII/agenda.shtml |date=8 November 2013 |work=] |access-date=28 January 2014}}</ref> <ref name="CAL-201311">{{cite web |author=Staff |title=Second Kepler Science Conference - NASA Ames Research Center, Mountain View, CA - Nov. 4-8, 2013 - Agenda |url=http://nexsci.caltech.edu/conferences/KeplerII/agenda.shtml |date=8 November 2013 |work=] |access-date=28 January 2014}}</ref>


<ref name="SL-20140128">{{cite news |last=Phil |first=Plait |author-link=Phil Plait |title=Astronomers Find Ancient Earth-Sized Planets in Our Galactic Backyard |url=http://www.slate.com/blogs/bad_astronomy/2015/01/27/exoplanets_five_extremely_old_planets_found_around_kepler_444.html |date=28 January 2015 |work=] |access-date=28 January 2015}}</ref> is more than 80% of the ]. <ref name="SL-20140128">{{cite news |last=Phil |first=Plait |author-link=Phil Plait |title=Astronomers Find Ancient Earth-Sized Planets in Our Galactic Backyard |url=http://www.slate.com/blogs/bad_astronomy/2015/01/27/exoplanets_five_extremely_old_planets_found_around_kepler_444.html |date=28 January 2015 |work=] |access-date=28 January 2015}}</ref> is more than 80% of the ].

<ref name="Weiss2024">{{cite journal | title=The Kepler Giant Planet Search. I. A Decade of Kepler Planet-host Radial Velocities from W. M. Keck Observatory | last1=Weiss | first1=Lauren M. | last2=Isaacson | first2=Howard | last3=Howard | first3=Andrew W. | last4=Fulton | first4=Benjamin J. | last5=Petigura | first5=Erik A. | last6=Fabrycky | first6=Daniel | last7=Jontof-Hutter | first7=Daniel | last8=Steffen | first8=Jason H. | last9=Schlichting | first9=Hilke E. | last10=Wright | first10=Jason T. | last11=Beard | first11=Corey | last12=Brinkman | first12=Casey L. | last13=Chontos | first13=Ashley | last14=Giacalone | first14=Steven | last15=Hill | first15=Michelle L. | last16=Kosiarek | first16=Molly R. | last17=MacDougall | first17=Mason G. | last18=Močnik | first18=Teo | last19=Polanski | first19=Alex S. | last20=Turtelboom | first20=Emma V. | last21=Tyler | first21=Dakotah | last22=Van Zandt | first22=Judah | display-authors=1 | journal=The Astrophysical Journal Supplement Series | volume=270 | issue=1 | date=2024-01-01 | article-number=8 | page=<!-- to prevent citation bot adding nonexistent page number--> | arxiv=2304.00071 | bibcode=2024ApJS..270....8W | bibcode-access=free | doi=10.3847/1538-4365/ad0cab | doi-access=free }}</ref>


<ref name=wilson1962>{{cite journal |bibcode=1962ApJ...136..793W |title=Relationship Between Colors and Spectra of Late Main-Sequence Stars |last1=Wilson |first1=O. C. |journal=The Astrophysical Journal |year=1962 |volume=136 |page=793 |doi=10.1086/147437 |doi-access=free }}</ref> <ref name=wilson1962>{{cite journal |bibcode=1962ApJ...136..793W |title=Relationship Between Colors and Spectra of Late Main-Sequence Stars |last1=Wilson |first1=O. C. |journal=The Astrophysical Journal |year=1962 |volume=136 |page=793 |doi=10.1086/147437 |doi-access=free }}</ref>
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<ref name=Stalport2022>{{cite journal | arxiv=2209.06810 | doi=10.1051/0004-6361/202243971 | bibcode=2022A&A...667A.128S | title=Global dynamics and architecture of the Kepler-444 system | year=2022 | last1=Stalport | first1=M. | last2=Matthews | first2=E. C. | last3=Bourrier | first3=V. | last4=Leleu | first4=A. | last5=Delisle | first5=J.-B. | last6=Udry | first6=S. | journal=Astronomy & Astrophysics | volume=667 | pages=A128 | s2cid=252222215 }}</ref> <ref name=Stalport2022>{{cite journal | arxiv=2209.06810 | doi=10.1051/0004-6361/202243971 | bibcode=2022A&A...667A.128S | title=Global dynamics and architecture of the Kepler-444 system | year=2022 | last1=Stalport | first1=M. | last2=Matthews | first2=E. C. | last3=Bourrier | first3=V. | last4=Leleu | first4=A. | last5=Delisle | first5=J.-B. | last6=Udry | first6=S. | journal=Astronomy & Astrophysics | volume=667 | pages=A128 | s2cid=252222215 }}</ref>
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<ref name=Zhang2023>{{cite journal |doi=10.3847/1538-3881/aca88c |title=The McDonald Accelerating Stars Survey: Architecture of the Ancient Five-planet Host System Kepler-444 |year=2023 |last1=Zhang |first1=Zhoujian |last2=Bowler |first2=Brendan P. |last3=Dupuy |first3=Trent J. |last4=Brandt |first4=Timothy D. |last5=Brandt |first5=G. Mirek |last6=Cochran |first6=William D. |last7=Endl |first7=Michael |last8=MacQueen |first8=Phillip J. |last9=Kratter |first9=Kaitlin M. |last10=Isaacson |first10=Howard T. |last11=Franson |first11=Kyle |last12=Kraus |first12=Adam L. |last13=Morley |first13=Caroline V. |last14=Zhou |first14=Yifan |journal=The Astronomical Journal |volume=165 |issue=2 |page=73 |arxiv=2210.07252 |bibcode=2023AJ....165...73Z |s2cid=252907948 |doi-access=free }}</ref> <ref name=Zhang2023>{{cite journal | title=The McDonald Accelerating Stars Survey: Architecture of the Ancient Five-planet Host System Kepler-444 | last1=Zhang | first1=Zhoujian | last2=Bowler | first2=Brendan P. | last3=Dupuy | first3=Trent J. | last4=Brandt | first4=Timothy D. | last5=Brandt | first5=G. Mirek | last6=Cochran | first6=William D. | last7=Endl | first7=Michael | last8=MacQueen | first8=Phillip J. | last9=Kratter | first9=Kaitlin M. | last10=Isaacson | first10=Howard T. | last11=Franson | first11=Kyle | last12=Kraus | first12=Adam L. | last13=Morley | first13=Caroline V. | last14=Zhou | first14=Yifan | display-authors=1 | journal=The Astronomical Journal | volume=165 | issue=2 | article-number=73 | page=<!-- to prevent citation bot adding nonexistent page number--> | year=2023 | arxiv=2210.07252 | bibcode=2023AJ....165...73Z | bibcode-access=free | doi=10.3847/1538-3881/aca88c | doi-access=free }}</ref>
}} }}


Latest revision as of 00:31, 18 November 2024

Triple star system in the constellation of Lyra
Kepler-444

Adaptive optics image of the Kepler-444 system from Zhang et al.
Observation data
Epoch J2000      Equinox 2000
Constellation Lyra
Kepler-444 A
Right ascension 19 19 00.5489
Declination +41° 38′ 04.582″
Apparent magnitude (V) 8.86
Kepler-444 B/C
Right ascension 19 19 00.3922
Declination +41° 38′ 04.013″
Characteristics
Spectral type K0V
Astrometry
Kepler-444 A
Radial velocity (Rv)−123.05±0.17 km/s
Proper motion (μ) RA: 94.639(13) mas/yr
Dec.: −632.269(14) mas/yr
Parallax (π)27.3578 ± 0.0125 mas
Distance119.22 ± 0.05 ly
(36.55 ± 0.02 pc)
Kepler-444 B/C
Proper motion (μ) RA: 94.508(55) mas/yr
Dec.: −630.781(78) mas/yr
Parallax (π)27.6079 ± 0.0545 mas
Distance118.1 ± 0.2 ly
(36.22 ± 0.07 pc)
Orbit
PrimaryA
CompanionBC
Period (P)324+31
−25 yr
Semi-major axis (a)52.2+3.3
−2.7 AU
Eccentricity (e)0.55+0.05
−0.05
Inclination (i)85.4+0.3
−0.4°
Longitude of the node (Ω)250.7+0.2
−0.2°
Periastron epoch (T)JD 2537060+10881
−8533
Argument of periastron (ω)
(secondary)		227.3+6.5
−5.2°
Details
A
Mass0.754±0.030 M☉
Radius0.753±0.010 R☉
Surface gravity (log g)4.595±0.060 cgs
Temperature5046±74.0 K
Metallicity −0.55±0.07 dex
Rotation49.40±6.04 d
Age11.00±0.8 Gyr
B
Mass0.307+0.009
−0.008 M☉
Surface gravity (log g)5.0±0.2 cgs
Temperature3,464±200 K
C
Mass0.296±0.008 M☉
Surface gravity (log g)~5 cgs
Temperature3,500 - 4,000 K
Other designations
BD+41°3306, WDS J19190+4138, KOI-3158, KIC 6278762, 2MASS J19190052+4138043
Kepler-444A: Gaia DR2 2101486923385239808, HIP 94931, LHS 3450, TYC 3129-00329-1, 2MASS J19190052+4138043
Kepler-444BC: Gaia DR2 2101486923382009472
Database references
SIMBADdata
B/C
Exoplanet Archivedata

Kepler-444 (or KOI-3158, KIC 6278762, 2MASS J19190052+4138043, BD+41°3306) is a triple star system, estimated to be 11.2 billion years old (more than 80% of the age of the universe), approximately 119 light-years (36 pc) away from Earth in the constellation Lyra. On 27 January 2015, the Kepler spacecraft is reported to have confirmed the detection of five sub-Earth-sized rocky exoplanets orbiting the main star. The star is a K-type main sequence star. All of the planets are far too close to their star to harbour life forms.

Discovery

Preliminary results of the planetary system around Kepler-444 were first announced at the second Kepler Science Conference in 2013. At that conference, the star was known as KOI-3158.

Characterization of the host star with asteroseismology was supported in part by the Nonprofit Adopt a Star program operated by White Dwarf Research Corporation, a crowd funded non-profit organization.

History

On 28 January 2015, astronomers using data from NASA's Kepler Mission discovered an ancient triple star system with five Earth-sized planets in Kepler-444. Evidential speculations in research show Kepler-444 formed 11.2 billion years ago, when the universe was less than 20 percent of its current age, making it two and a half times older than the Earth.

Characteristics

The star, Kepler-444, is approximately 11.2 billion years old, whereas the Sun is only 4.6 billion years old. The age is that of Kepler-444 A, an orange main sequence star of spectral type K0. Despite this great age, it is in middle of its main-sequence lifespan, much like the Sun.

The original research on Kepler-444 was published in The Astrophysical Journal on 27 January 2015 under the title "An ancient extrasolar system with five sub-Earth-size planets" by a team of 40 authors.

Stellar system

Diagram showing the change in radial velocity over time caused by the orbiting M dwarf pair.
Radial velocity time series of Kepler 444 showing linear trend in velocities caused by the pair of M-dwarf stars from Weiss et al.

The Kepler-444 system consists of the planet hosting primary and a pair of M-dwarf stars. The M-dwarfs orbit each other at a distance of less than 0.3 AU while the pair orbits the primary in a highly eccentric 324-year orbit. The pair comes within 23.55 AU of the primary potentially truncating the protoplanetary disk from which the planets formed at 8 AU. This would have depleted the availability of solid material to form the observed planets.

Previous stellar orbit solution was ever more extreme, period was shorter (211 years) and eccentricity was much larger (e=0.865), moving periastron to 5 AU, severely reducing the estimated protoplanetary disk size to 1–2 AU and its estimated mass from ~600 to ~4 Earth masses.

Radial velocity measurements of Kepler-444 show a linear trend, which aligns well with the orbit outlined by Dupuy et al. (see diagram above)

Planetary system

All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed, smaller than the size of Venus (but bigger than Mercury) and each of the exoplanets completes an orbit around the host star in less than 10 days. Thus, the planetary system is very compact, as even the furthest known planet, Kepler-444f, still orbits closer to the star than Mercury is to the Sun. According to NASA, no life as we know it could exist on these hot exoplanets, due to their close orbital distances to the host star. To keep the known planetary system stable, no additional giant planets can be located within 5.5 AU of the parent star.

Moreover, the system is pervaded by high-order resonance chain: period ratios are 4:5, 3:4, 4:5, 4:5. This tight chain is unperturbed and very likely continues farther from Kepler-444A.

A marginally significant peak appears at 72 days in the radial velocity data when the linear trend attributed to the stellar companions is subtracted. However, this signal suggests an eccentricity that is unphysically high, leading to orbits that would intersect the known planets. The signal likely stems from complexities within the long-term radial velocity signal of the Kepler-444 ABC system and may also be associated with the orbit of the BC pair.

The Kepler-444 planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b <0.079 M🜨 0.04178±0.00079 3.6001053+0.0000083
−0.0000080 		0.16+0.21
−0.10 		88.0+1.2
−0.6° 		0.406+0.013
−0.013 R🜨
c <0.16 M🜨 0.04881±0.00093 4.5458841+0.0000070
−0.0000071 		0.31+0.12
−0.15 		88.2+1.2
−1.0° 		0.521+0.017
−0.016 R🜨
d 0.036+0.065
−0.020 M🜨 		0.0600±0.0011 6.189392+0.000012
−0.000012 		0.18+0.16
−0.12 		88.16+0.81
−0.55° 		0.540+0.017
−0.016 R🜨
e 0.034+0.059
−0.019 M🜨 		0.0696±0.0013 7.743493+0.000017
−0.000016 		0.10+0.20
−0.07 		89.13+0.54
−0.52° 		0.555+0.018
−0.016 R🜨
f <0.22 M🜨 0.0811±0.0015 9.740486+0.000013
−0.000013 		0.29+0.20
−0.19 		87.96+0.36
−0.31° 		0.767+0.025
−0.024 R🜨

See also

Notes

  1. The eccentricity has a non-Gaussian posterior distribution and so the median is an overestimate of the true eccentricity.

References

  1. ^ Zhang, Zhoujian; et al. (2023). "The McDonald Accelerating Stars Survey: Architecture of the Ancient Five-planet Host System Kepler-444". The Astronomical Journal. 165 (2) 73. arXiv:2210.07252. Bibcode:2023AJ....165...73Z. doi:10.3847/1538-3881/aca88c.
  2. ^ Campante, T. L.; et al. (2015). "An Ancient Extrasolar System with Five Sub-Earth-size Planets". The Astrophysical Journal. 799 (2) 170. arXiv:1501.06227. Bibcode:2015ApJ...799..170C. doi:10.1088/0004-637X/799/2/170.
  3. ^ 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.
  4. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.</ref
  5. ^ 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.
  6. Wilson, O. C. (1962). "Relationship Between Colors and Spectra of Late Main-Sequence Stars". The Astrophysical Journal. 136: 793. Bibcode:1962ApJ...136..793W. doi:10.1086/147437.
  7. ^ Dupuy, Trent J.; et al. (2016). "Orbital Architectures of Planet-Hosting Binaries. I. Forming Five Small Planets in the Truncated Disk of Kepler-444A". The Astrophysical Journal. 817 (1) 80. arXiv:1512.03428. Bibcode:2016ApJ...817...80D. doi:10.3847/0004-637X/817/1/80.
  8. ^ Buldgen, G.; et al. (2019). "Revisiting Kepler-444. I. Seismic modeling and inversions of stellar structure". Astronomy & Astrophysics. 630. A126. arXiv:1907.10315. Bibcode:2019A&A...630A.126B. doi:10.1051/0004-6361/201936126. S2CID 198229778.
  9. Mazeh, Tsevi; et al. (2015). "Photometric Amplitude Distribution of Stellar Rotation of KOIs—Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars". The Astrophysical Journal. 801 (1). 3. arXiv:1501.01288. Bibcode:2015ApJ...801....3M. doi:10.1088/0004-637X/801/1/3.
  10. ^ "BD+41 3306". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 August 2020.
  11. "BD+41 3306B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 August 2020.
  12. ^ Wall, Mike (27 January 2015). "Found! 5 Ancient Alien Planets Nearly As Old As the Universe". Space.com. Retrieved 27 January 2015.
  13. ^ Johnson, Michele (28 January 2015). "Astronomers Discover Ancient System with Five Small Planets". NASA. Retrieved 29 January 2015.
  14. Dunn, Marcia (27 January 2015). "Astronomers find solar system more than double ours in age". AP News. Retrieved 27 January 2015.
  15. ^ Atkinson, Nancy (27 January 2015). "Oldest Planetary System Discovered, Improving the Chances for Intelligent Life Everywhere". Universe Today. Retrieved 27 January 2015.
  16. Staff (8 November 2013). "Second Kepler Science Conference - NASA Ames Research Center, Mountain View, CA - Nov. 4-8, 2013 - Agenda". Caltech. Retrieved 28 January 2014.
  17. ^ Phil, Plait (28 January 2015). "Astronomers Find Ancient Earth-Sized Planets in Our Galactic Backyard". Slate. Retrieved 28 January 2015.
  18. ^ Weiss, Lauren M.; et al. (1 January 2024). "The Kepler Giant Planet Search. I. A Decade of Kepler Planet-host Radial Velocities from W. M. Keck Observatory". The Astrophysical Journal Supplement Series. 270 (1) 8. arXiv:2304.00071. Bibcode:2024ApJS..270....8W. doi:10.3847/1538-4365/ad0cab.
  19. Becker, Juliette C.; Adams, Fred C. (2017), "Effects of Unseen Additional Planetary Perturbers on Compact Extrasolar Planetary Systems", Monthly Notices of the Royal Astronomical Society, 468 (1): 549–563, arXiv:1702.07714, Bibcode:2017MNRAS.468..549B, doi:10.1093/mnras/stx461, S2CID 119325005
  20. Mills, Sean M.; Fabrycky, Daniel C. (2017). "Mass, Density, and Formation Constraints in the Compact, Sub-Earth Kepler-444 System including Two Mars-mass Planets". The Astrophysical Journal Letters. 838 (1) L11. arXiv:1703.03417. Bibcode:2017ApJ...838L..11M. doi:10.3847/2041-8213/aa6543.

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