Kepler-444

Kepler-444
Observation data
Epoch J2000      Equinox 2000
Constellation Lyra
Right ascension 19h 19m 01.0s[1]
Declination +41° 38′ 05″[1]
Apparent magnitude (V) 8.86
Characteristics
Spectral type K0V
Astrometry
Radial velocity (Rv)−121.19±0.11 km/s
Proper motion (μ) RA: 98.94±0.80[1] mas/yr
Dec.: −632.49±0.85[1] mas/yr
Parallax (π)28.03 ± 0.82[1] mas
Distance116 ± 3 ly
(36 ± 1 pc)
Details
Mass0.758 (± 0.043) M☉
Radius0.752 (± 0.014) R☉
Temperature5040 (± 74.0) K
Metallicity [Fe/H]-0.55 (± 0.07) dex
Rotation49.40±6.04 d[2]
Age11.23 (± 0.99) Gyr
Other designations
KOI-3158; 2MASS J19190052+4138043; TYC 3129-00329-1; KIC 6278762; LHS 3450; HIP 94931; BD+41 3306
Database references
SIMBADdata

Kepler-444 (or KOI-3158, KIC 6278762, 2MASS J19190052+4138043, BD+41 3306)[3][4][5][6][7][8] is a star, estimated to be 11.2 billion years old (more than 80% of the age of the universe),[6] approximately 116 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 star.[3][4][5][7] 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.[3]

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.[9]

Characteristics

The star, Kepler-444, is approximately 11.2 billion years old, whereas the Sun is only 4.6 billion years old. The age of Kepler-444, an orange main sequence star of spectral type K0,[8] is more than 80% of the age of the universe.[6]

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"[10] by a team of 40 authors, the abstract reads as follows:

The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich. 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 Galactic thick disk 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 transit photometry. Kepler-444 is the densest star with detected solar-like oscillations. We use asteroseismology 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 terrestrial-size planets. 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 Galaxy. 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 planet formation."[10] 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.[11]

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 AU while the pair orbits the primary in a highly eccentric 198 year orbit. The pair comes within 5 AU of the primary potentially severely truncating the protoplanetary disk from which the planets formed at 1–2 AU. This would have depleted the availability of solid material to form the observed planets.[12]

Planetary system

All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed,[7] 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.[3][6] The system is also very compact and Kepler-444b is the smallest at 0.403 earth diameters, and even the furthest planet, Kepler-444f, still orbits closer to the star than Mercury is to the Sun.[8] 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.[3]

The Kepler-444 planetary system[7][13]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b — 0.04178 3.60001053 0.16 88° 0.4 R⊕
c — 0.04881 4.5458841 0.31 88.2° 0.497 R⊕
d 0.036+0.065
−0.020 M⊕		 0.06 6.189392 0.18 88.16° 0.53 R⊕
e 0.034+0.059
−0.019 M⊕		 0.0696 7.743493 0.1 89.13° 0.546 R⊕
f — 0.0811 9.740486 0.29 87.96° 0.741 R⊕

See also

References

  1. 1 2 3 4 5 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ↑ 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.
  3. 1 2 3 4 5 Johnson, Michele (28 January 2015). "Astronomers Discover Ancient System with Five Small Planets". NASA. Retrieved 29 January 2015.
  4. 1 2 Dunn, Marcia (27 January 2015). "Astronomers find solar system more than double ours in age". AP News. Retrieved 27 January 2015.
  5. 1 2 Atkinson, Nancy (27 January 2015). "Oldest Planetary System Discovered, Improving the Chances for Intelligent Life Everywhere". Universe Today. Retrieved 27 January 2015.
  6. 1 2 3 4 Wall, Mike (27 January 2015). "Found! 5 Ancient Alien Planets Nearly As Old As the Universe". Space.com. Retrieved 27 January 2015.
  7. 1 2 3 4 Staff (27 January 2015). "Exoplanet Catalog". Extrasolar Planets Encyclopaedia. Retrieved 27 January 2015.
  8. 1 2 3 Phil, Plait (28 January 2015). "Astronomers Find Ancient Earth-Sized Planets in Our Galactic Backyard". Slate. Retrieved 28 January 2015.
  9. ↑ 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.
  10. 1 2 Campante, T.L.; et al. (27 January 2015). "An Ancient Extrasolar System with Five Sub-Earth-size Planets". Astrophysical Journal. 799 (2). arXiv:1501.06227. Bibcode:2015ApJ...799..170C. doi:10.1088/0004-637X/799/2/170. Retrieved 2 February 2015.
  11. ↑ Campante, Tiago (18 September 2014). "An ancient extrasolar system with five sub-Earth-size planets" (PDF): 6–15. Retrieved 2 February 2015.
  12. ↑ 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.
  13. ↑ 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.

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

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