EZ Aquarii is a triple star system 11.1 light-years (3.4 parsecs) from the Sun in the constellation Aquarius within the Milky Way. It is also known as Luyten 789-6, Gliese 866 and LHS 68. It is a variable star showing flares as well as smaller brightness changes due to rotation. The aggregate mass of the system is 0.3262±0.0018 solar masses.[8] All three seem to have masses close to the hydrogen burning mass limit.[10]
EZ Aquarii Star System. Credit: SpaceEngine/Bob Trembley | |
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius |
Right ascension | 22h 38m 33.73s[1] |
Declination | −15° 17′ 57.3″[1] |
Apparent magnitude (V) | 12.38[2] (13.03/13.27/15.07)[3] |
Characteristics | |
Spectral type | M5 V[3] |
B−V color index | +1.96[4] |
Variable type | Flare star + BY Dra[5] |
Astrometry | |
Radial velocity (Rv) | −59.9[6] km/s |
Proper motion (μ) | RA: +2314[7] mas/yr Dec.: +2295[7] mas/yr |
Parallax (π) | 293.6 ± 0.9 mas[8] |
Distance | 11.11 ± 0.03 ly (3.41 ± 0.01 pc) |
Absolute magnitude (MV) | 14.75[9] (15.33/15.58/17.37)[3] |
Orbit[10] | |
Primary | EZ Aquarii AC |
Companion | EZ Aquarii B |
Period (P) | 2.2506±0.0033 yr |
Semi-major axis (a) | 0.346±0.004″ |
Eccentricity (e) | 0.437±0.007 |
Inclination (i) | 112.4±0.5° |
Longitude of the node (Ω) | 162.1±0.4° |
Periastron epoch (T) | 1987.236 ± 0.014 |
Argument of periastron (ω) (secondary) | −17.7±1.1° |
Details | |
EZ Aquarii A | |
Mass | 0.1187±0.0011[8] M☉ |
Radius | 0.175[11] R☉ |
Luminosity | 0.00078[8] L☉ |
EZ Aquarii C | |
Mass | 0.0930±0.0008[8] M☉ |
Luminosity | 0.00012[8] L☉ |
EZ Aquarii B | |
Mass | 0.1145±0.0012[8] M☉ |
Radius | 0.21±0.04[8] R☉ |
Temperature | 2650±200[8] K |
Other designations | |
Database references | |
SIMBAD | data |
EZ Location of EZ Aquarii in the constellation Aquarius |
The configuration of the inner binary pair may permit a circumbinary planet to orbit near their habitable zone, however no exoplanets have yet been observed.[14] EZ Aquarii is approaching the Solar System and, in about 32,300 years, will be at its minimal distance of about 8.2 ly (2.5 pc) from the Sun.[15] The ChView simulation shows that currently its nearest neighbouring star is Lacaille 9352 at about 4.1 ly (1.3 pc) from EZ Aquarii.
All three components are M-type red dwarfs. The pair EZ Aquarii AC form a spectroscopic binary with a 3.8-day orbit and a 0.03 AU separation. This pair share an orbit with EZ Aquarii B that has an 823-day period.[17] The A and B components of Luyten 789-6 together emit X-rays.[18]
This star is a red dwarf of type M5V[3] which has a mass of 0.1187±0.0011 solar masses.[8] It has a parallax of 293.6±0.9 mas.[19] Its period in days around EZ Aquarii C is 3.786516±0.000005 d with an eccentricity of 0 which together make up the primary of the system.[19] It has an absolute magnitude at wavelengths centered at 5500 Angstroms of 15.33 making it the brightest of the three.[3] Some alternate designations for it are EZ Aqr, GL 866A, L 789-6 A and LHS 68.
There is less known about this star compared to A. Its type is likely a type MV[3] with a mass of 0.1145±0.0012 solar masses.[8] It orbits the AC system with a period of 822.6±0.2 d at an eccentricity of 0.439±0.001.[19] It has an absolute magnitude of 15.58, making it dimmer than A but brighter than C.[3] Some alternate designations for it are GL 866B and L 789-6 B.
Like the other two, this star is likely a type MV[3] with a mass of 0.0930±0.0008 solar masses.[8] It orbits A in a period of 3.786516±0.000005 d with a nearly circular orbit.[19] It is the dimmest of the three with an absolute magnitude of 17.37.[3] An alternate designation for it is GL 866C.
The high proper motion of EZ Aquarii may have been discovered by Willem Jacob Luyten with his automated photographic plate scanner.[20]