Kepler-444
| Observation data Epoch J2000 Equinox 2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19:19:01.0 |
| Declination | +41:38:05 |
| Apparent magnitude (V) | 9.0 |
| Characteristics | |
| Spectral type | K0V C ~ |
| Apparent magnitude (U) | 10.01 ~ |
| Apparent magnitude (B) | 9.67 ~ |
| Apparent magnitude (V) | 8.86 ~ |
| Apparent magnitude (R) | 8.18 ~ |
| Apparent magnitude (I) | 7.66 ~ |
| Apparent magnitude (J) | 7.244±0.026 |
| Apparent magnitude (H) | 6.772±0.047 |
| Apparent magnitude (K) | 6.703±0.020 |
| Astrometry | |
| Radial velocity (Rv) | −121.19±0.11 km/s |
| Proper motion (μ) | RA: 98.94 mas/yr Dec.: -632.49 mas/yr |
| Parallax (π) | 28.03±0.82 mas |
| Distance | 117 ly (36 pc) |
| Details | |
| Mass | 0.758 (± 0.043) M☉ |
| Radius | 0.752 (± 0.014) R☉ |
| Temperature | 5040 (± 74.0) K |
| Metallicity [Fe/H] | -0.55 (± 0.07) dex |
| Age | 11.23 (± 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 | |
| SIMBAD | data |
Kepler-444 (or KOI-3158, KIC 6278762, 2MASS J19190052+4138043, BD+41 3306)[1][2][3][4][5][6] is a star, estimated to be 11.2 billion years old (more than 80% of the age of the universe),[4] approximately 117 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.[1][2][3][5] 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.[1]
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.[7]
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,[6] is more than 80% of the age of the universe.[4]
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"[8][9] 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."[9] 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.[10]
Planetary system
| 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 | — | 0.06 | 6.189392 | 0.18 | 88.16° | 0.53 R🜨 |
| e | — | 0.0696 | 7.743493 | 0.1 | 89.13° | 0.546 R🜨 |
| f | — | 0.0811 | 9.740486 | 0.29 | 87.96° | 0.741 R🜨 |
All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed,[5] 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.[1][4] 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.[6] 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.[1]
See also
- Kepler-80 - most compact 5-planet system discovered so far
- List of extrasolar planets
- PSR B1620-26 - a possible ancient planetary system in Messier 4
References
- ^ a b c d e Johnson, Michele (28 January 2015). "Astronomers Discover Ancient System with Five Small Planets". NASA. Retrieved 29 January 2015.
- ^ a b Dunn, Marcia (27 January 2015). "Astronomers find solar system more than double ours in age". AP News. Retrieved 27 January 2015.
- ^ a b Atkinson, Nancy (27 January 2015). "Oldest Planetary System Discovered, Improving the Chances for Intelligent Life Everywhere". Universe Today. Retrieved 27 January 2015.
- ^ a b c d Wall, Mike (27 January 2015). "Found! 5 Ancient Alien Planets Nearly As Old As the Universe". Space.com. Retrieved 27 January 2015.
- ^ a b c d Staff (27 January 2015). "Exoplanet Catalog". Extrasolar Planets Encyclopaedia. Retrieved 27 January 2015.
- ^ a b c Phil, Plait (28 January 2015). "Astronomers Find Ancient Earth-Sized Planets in Our Galactic Backyard". Slate. Retrieved 28 January 2015.
- ^ 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.
- ^ 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.
- ^ a b Campante, T.L.; et al. (26 January 2015). "An ancient extrasolar system with five sub-Earth-size planets". Arxiv. arXiv:1501.06227. Bibcode:2015ApJ...799..170C. doi:10.1088/0004-637X/799/2/170. Retrieved 27 January 2015.
- ^ Campante, Tiago (18 September 2014). "An ancient extrasolar system with five sub-Earth-size planets" (PDF): 6–15. Retrieved 2 February 2015.
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