Kepler-444

Adaptive optics image of the Kepler-444 system from Zhang et al.[1]
Observation data Epoch J2000      Equinox 2000
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]
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)mas/yr[3] Dec.: −632.269(14)mas/yr[3]
Parallax (π)	27.3578±0.0125 mas[3]
Distance	119.22 ± 0.05 ly (36.55 ± 0.02 pc)
Kepler-444 B/C
Proper motion (μ)	RA: 94.508(55) mas/yr[5] Dec.: −630.781(78) mas/yr[5]
Parallax (π)	27.6079 ± 0.0545 mas[5]
Distance	118.1 ± 0.2 ly (36.22 ± 0.07 pc)
Orbit[1]
Primary	A
Companion	BC
Period (P)	324+31 −25yr
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°
Periastronepoch (T)	JD2537060+10881 −8533
Argument of periastron (ω) (secondary)	227.3+6.5 −5.2°
Details
A
Mass	0.754±0.030[8] M☉
Radius	0.753±0.010[8] R☉
Surface gravity (log g)	4.595±0.060[2] cgs
Temperature	5046±74.0[2] K
Metallicity [Fe/H]	−0.55±0.07[2] dex
Rotation	49.40±6.04 d[9]
Age	11.00±0.8[8] Gyr
B
Mass	0.307+0.009 −0.008[1] M☉
Surface gravity (log g)	5.0±0.2[2] cgs
Temperature	3,464±200[2] K
C
Mass	0.296±0.008[1] M☉
Surface gravity (log g)	~5[2] cgs
Temperature	3,500 - 4,000[2] 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
SIMBAD	data
	B/C
Exoplanet Archive	data

Kepler-444 (orKOI-3158,KIC 6278762,2MASS J19190052+4138043,BD+41°3306)^[10] is atriple star system, estimated to be 11.2 billion years old (more than 80% of the age of theuniverse),^[12] approximately 119 light-years (36 pc) away fromEarth in theconstellationLyra. On 27 January 2015, theKepler spacecraft is reported to have confirmed the detection of five sub-Earth-sizedrockyexoplanets orbiting the main star. The star is aK-type main sequence star.^{[13][14][15][12]} All of the planets are far too close to their star to harbour life forms.^[13]

Preliminary results of the planetary system around Kepler-444 were first announced at the secondKepler Science Conference in 2013. At that conference, the star was known as KOI-3158.^[16]

Characterization of the host star with asteroseismology was supported in part by theNonprofit Adopt a Star program operated by White Dwarf Research Corporation, acrowd funded non-profit organization.^[15]

On 28 January 2015, astronomers using data from NASA'sKepler Mission discovered an ancient triple star system with fiveEarth-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 theEarth.

The star, Kepler-444, is approximately 11.2 billion years old, whereas theSun is only 4.6 billion years old. The age is that of Kepler-444 A, anorange main sequence star of spectral type K0.^[17] 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 inThe 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]

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 0.3AU while the pair orbits the primary in a highlyeccentric 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]

Radial velocity measurements of Kepler-444 show a linear trend, which aligns well with the orbit outlined by Dupuy et al. (see diagram above)^[18]

All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed, smaller than the size ofVenus (but bigger thanMercury) 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 theSun.^[17] 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 5.5AU of the parent star.^[19]

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 aneccentricity 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.^[18]

• Kepler-80 - most compact 6-planet system discovered so far
• List of extrasolar planets
• PSR B1620-26 - an ancient planetary system inMessier 4

• NASA – Kepler-444/KOI-3158 atThe NASA Exoplanet Archive
• NASA – Kepler-444b/c/d/e/f atExtrasolar Planets Encyclopaedia

• Lyra
• Planetary systems with five confirmed planets
• K-type main-sequence stars
• Kepler objects of interest
• Planetary transit variables
• 2MASS objects
• Hipparcos objects
• Durchmusterung objects
• M-type main-sequence stars
• Triple star systems
• TIC objects

• Use dmy dates from January 2015
• Articles with short description
• Short description is different from Wikidata