Kepler-444

Adaptive optics image of the Kepler-444 system from Zhang et al.[1]
Observation data
Epoch J2000      Equinox 2000
Constellation Lyra
Kepler-444 A
Right ascension 19h 19m 00.5489s[2]
Declination +41° 38′ 04.582″[2]
Apparent magnitude (V) 8.86[3]
Kepler-444 B/C
Right ascension 19h 19m 00.3922s[4]
Declination +41° 38′ 04.013″[4]
Characteristics
Spectral type K0V[5]
Astrometry
Kepler-444 A
Radial velocity (Rv)−123.05±0.17[6] km/s
Proper motion (μ) RA: 94.639(13) mas/yr[2]
Dec.: −632.269(14) mas/yr[2]
Parallax (π)27.3578 ± 0.0125 mas[2]
Distance119.22 ± 0.05 ly
(36.55 ± 0.02 pc)
Kepler-444 B/C
Proper motion (μ) RA: 94.508(55) mas/yr[4]
Dec.: −630.781(78) mas/yr[4]
Parallax (π)27.6079 ± 0.0545 mas[4]
Distance118.1 ± 0.2 ly
(36.22 ± 0.07 pc)
Orbit[1]
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[7] M☉
Radius0.753±0.010[7] R☉
Surface gravity (log g)4.595±0.060[8] cgs
Temperature5046±74.0[8] K
Metallicity [Fe/H]−0.55±0.07[8] dex
Rotation49.40±6.04 d[9]
Age11.00±0.8[7] Gyr
B
Mass0.307+0.009
−0.008[1] M☉
Surface gravity (log g)5.0±0.2[8] cgs
Temperature3,464±200[8] K
C
Mass0.296±0.008[1] M☉
Surface gravity (log g)~5[8] cgs
Temperature3,500 - 4,000[8] 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[10]
Kepler-444BC: Gaia DR2 2101486923382009472[11]
Database references
SIMBADdata
B/C

Kepler-444 (or KOI-3158, KIC 6278762, 2MASS J19190052+4138043, BD+41°3306)[10] is a triple star system, estimated to be 11.2 billion years old (more than 80% of the age of the universe),[12] 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.[13][14][15][12][16] All of the planets are far too close to their star to harbour life forms.[13]

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.[17]

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.[15]

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.[18] 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.[8]

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.[19]

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.[1]

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.[6]

Planetary system

All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed,[16] 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.[13][12] 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.[18] 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.[13] To keep the known planetary system stable, no additional giant planets can be located within 5.5 AU of the parent star.[20]

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.

The Kepler-444 planetary system[16][21]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b — 0.04178 3.600105+0.000031
−0.000037		 0.16 88° 0.406±0.013 R🜨
c — 0.04881 4.545876±0.000031 0.31 88.2° 0.521±0.017 R🜨
d 0.036+0.065
−0.020 M🜨		 0.06 6.189437+0.000053
−0.000037		 0.18 88.16° 0.54±0.017 R🜨
e 0.034+0.059
−0.019 M🜨		 0.0696 7.743467+0.00006
−0.0001		 0.1 89.13° 0.555+0.018
−0.016 R🜨
f — 0.0811 9.740501+0.000078
−0.000026		 0.29 87.96° 0.767±0.025 R🜨

See also

References

  1. 1 2 3 4 5 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. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. ↑ 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
  4. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  5. ↑ 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.
  6. 1 2 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.
  7. 1 2 3 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.
  8. 1 2 3 4 5 6 7 8 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.
  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. 1 2 "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. 1 2 3 Wall, Mike (27 January 2015). "Found! 5 Ancient Alien Planets Nearly As Old As the Universe". Space.com. Retrieved 27 January 2015.
  13. 1 2 3 4 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. 1 2 Atkinson, Nancy (27 January 2015). "Oldest Planetary System Discovered, Improving the Chances for Intelligent Life Everywhere". Universe Today. Retrieved 27 January 2015.
  16. 1 2 3 Staff (27 January 2015). "Exoplanet Catalog". Extrasolar Planets Encyclopaedia. Retrieved 27 January 2015.
  17. ↑ 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.
  18. 1 2 Phil, Plait (28 January 2015). "Astronomers Find Ancient Earth-Sized Planets in Our Galactic Backyard". Slate. Retrieved 28 January 2015.
  19. ↑ 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.
  20. ↑ 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
  21. ↑ 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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