Astronomy:Kepler-444

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Short description: Triple star system in the constellation of Lyra
Kepler-444
Adaptive optics image of the Kepler-444 system.jpg
Adaptive optics image of the Kepler-444 system from Zhang et al.[1]
Observation data
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
Constellation Lyra[2]
Kepler-444 A
Right ascension  19h 19m 00.5489s[3]
Declination +41° 38′ 04.582″[3]
Apparent magnitude (V) 8.86[4]
Kepler-444 B/C
Right ascension  19h 19m 00.3922s[5]
Declination +41° 38′ 04.013″[5]
Apparent magnitude (V)
Characteristics
Spectral type K0V[6]
Astrometry
Kepler-444 A
Radial velocity (Rv)−123.05±0.17[7] km/s
Proper motion (μ) RA: 94.639(13)[3] mas/yr
Dec.: −632.269(14)[3] mas/yr
Parallax (π)27.3578 ± 0.0125[3] 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[5] mas
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[8] M☉
Radius0.753±0.010[8] R☉
Surface gravity (log g)4.595±0.060[2] cgs
Temperature5046±74.0[2] K
Metallicity [Fe/H]−0.55±0.07[2] dex
Rotation49.40±6.04 d[9]
Age11.00±0.8[8] Gyr
B
Mass0.307+0.009
−0.008[1] M☉
Surface gravity (log g)5.0±0.2[2] cgs
Temperature3,464±200[2] K
C
Mass0.296±0.008[1] M☉
Surface gravity (log g)~5[2] cgs
Temperature3,500 - 4,000[2] K
Other designations
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.[2]

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.[7]

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. ↑ 1.0 1.1 1.2 1.3 1.4 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). doi:10.3847/1538-3881/aca88c. Bibcode: 2023AJ....165...73Z. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Campante, T. L. et al. (2015). "An Ancient Extrasolar System with Five Sub-Earth-size Planets". The Astrophysical Journal 799 (2). doi:10.1088/0004-637X/799/2/170. Bibcode: 2015ApJ...799..170C. 
  3. ↑ 3.0 3.1 3.2 3.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  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. ↑ 5.0 5.1 5.2 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  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. doi:10.1086/147437. Bibcode: 1962ApJ...136..793W. 
  7. ↑ 7.0 7.1 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). doi:10.3847/0004-637X/817/1/80. Bibcode: 2016ApJ...817...80D. 
  8. ↑ 8.0 8.1 8.2 Buldgen, G. et al. (2019). "Revisiting Kepler-444. I. Seismic modeling and inversions of stellar structure". Astronomy & Astrophysics 630: A126. doi:10.1051/0004-6361/201936126. Bibcode: 2019A&A...630A.126B. 
  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. doi:10.1088/0004-637X/801/1/3. Bibcode: 2015ApJ...801....3M. 
  10. ↑ 10.0 10.1 "BD+41 3306". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=BD%2B41+3306. 
  11. ↑ "BD+41 3306B". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=BD%2B41+3306B. 
  12. ↑ 12.0 12.1 12.2 Wall, Mike (27 January 2015). "Found! 5 Ancient Alien Planets Nearly As Old As the Universe". Space.com. http://www.space.com/28386-ancient-alien-planets-discovery-kepler-444.html. 
  13. ↑ 13.0 13.1 13.2 13.3 Johnson, Michele (28 January 2015). "Astronomers Discover Ancient System with Five Small Planets". NASA. https://www.jpl.nasa.gov/news/astronomers-discover-ancient-system-with-five-small-planets. 
  14. ↑ Dunn, Marcia (27 January 2015). "Astronomers find solar system more than double ours in age". AP News. https://apnews.com/general-news-1b42cd9c22fa48a6b57fcbe1dccbd617. 
  15. ↑ 15.0 15.1 Atkinson, Nancy (27 January 2015). "Oldest Planetary System Discovered, Improving the Chances for Intelligent Life Everywhere". Universe Today. http://www.universetoday.com/118510/oldest-planetary-system-discovered-improving-the-chances-for-intelligent-life-everywhere/. 
  16. ↑ 16.0 16.1 16.2 Staff (27 January 2015). "Exoplanet Catalog". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/. 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. http://nexsci.caltech.edu/conferences/KeplerII/agenda.shtml. 
  18. ↑ 18.0 18.1 Phil, Plait (28 January 2015). "Astronomers Find Ancient Earth-Sized Planets in Our Galactic Backyard". Slate. http://www.slate.com/blogs/bad_astronomy/2015/01/27/exoplanets_five_extremely_old_planets_found_around_kepler_444.html. 
  19. ↑ Weiss, Lauren M. et al. (2024-01-01). "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). doi:10.3847/1538-4365/ad0cab. Bibcode: 2024ApJS..270....8W. 
  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, doi:10.1093/mnras/stx461, Bibcode: 2017MNRAS.468..549B 
  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). doi:10.3847/2041-8213/aa6543. Bibcode: 2017ApJ...838L..11M. 

External links

Coordinates: Sky map 19h 19m 01.0s, +41° 38′ 05″



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