| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pisces |
| Right ascension | 23h 09m 10.72701s[1] |
| Declination | −02° 15′ 38.6854″[1] |
| Apparent magnitude (V) | 8.628[2] |
| Characteristics | |
| Spectral type | K3 V[3] |
| B−Vcolor index | 1.014[3] |
| Astrometry | |
| Radial velocity (Rv) | −37.800±0.0029[4] km/s |
| Proper motion (μ) | RA: +631.520[1]mas/yr Dec.: −97.214[1]mas/yr |
| Parallax (π) | 34.6603±0.0511 mas[1] |
| Distance | 94.1 ± 0.1 ly (28.85 ± 0.04 pc) |
| Absolute magnitude (MV) | 6.187[3] |
| Details | |
| Mass | 0.81±0.06[5] M☉ |
| Radius | 0.86±0.08[2] R☉ |
| Luminosity | 0.353±0.032[2] L☉ |
| Surface gravity (log g) | 4.48±0.04[5] cgs |
| Temperature | 4,849±42[5] K |
| Metallicity [Fe/H] | 0.38[3] dex |
| Rotational velocity (v sin i) | 0.0 km/s |
| Age | 8.5[2] to 11.5[5] Gyr |
| Other designations | |
| Ebla[6][7],BD−03°5577,HD 218566,HIP 114322,SAO 146533[8] | |
| Database references | |
| SIMBAD | data |
HD 218566 is astar in theequatorialzodiacconstellation ofPisces. It has the proper nameEbla, after a kingdom in ancient Syria. With anapparent visual magnitude of 8.6,[2] this ninth magnitude star can not be viewed with the naked eye. However, it can be readily seen even with a small telescope.[9] It is located at a distance of 94 light years from theSun based onparallax, but is drifting closer with aradial velocity of −37.8 km/s.[4] The star hosts one knownexoplanet, HD 218566 b.[2]
The name Ebla was selected in theNameExoWorlds campaign bySyria, during the 100th anniversary of theIAU.Ebla was one of the earliest kingdoms in Syria. At this time, the planet HD 218566 b was namedUgarit.Ugarit was a city where its scribes devised theUgaritic alphabet around 1400 B.C.[6][7]
HD 218566 is a smaller star than the Sun, with about 81%[5] of the Sun's mass and 86% of the radius of the Sun.[2] It is aK-type main sequence star with astellar classification of K3 V[3] that is generating energy by thenuclear fusion of hydrogen at its core. HD 218556 is radiating around 35% of the luminosity of the Sun from its outer envelope at aneffective temperature of 4,849 K.[5] This heat gives the star the characteristic orange-hued glow of a K-type star.[10]
Compared to the Sun, this star has an unusually high abundance of elements other than hydrogen and helium, what astronomers term themetallicity. Based upon the abundance of iron, the metallicity is 2.4 times as high as in the Sun.[2] It is much older than the Sun, with estimates of its age ranging from 8.5[2] to 11.5[5] billion years. It appears to have a negligible rate of spin as itsprojected rotational velocity is too small to measure.[2]
This star belongs to the thick disk population of the Milky Way. In thegalactic coordinate system, it hasspace velocity components of [U, V, W] = [77, −61, −8] km/s. HD 218556 is following an orbit through the galaxy with aneccentricity of0.36±0.01 that carries it as close as 14.3 kly (4.4 kpc) and as far as 30.3 kly (9.3 kpc) from theGalactic Center. The orbital tilt carries this star as much as 0.6 kly (0.18 kpc) from thegalactic plane.[5]
Based upon high resolution measurements performed at theW. M. Keck Observatory and analysis performed upon these measurements by amateur astronomerPeter Jalowiczor, HD 218566 shows cyclical variations inradial velocity that suggestgravitational perturbation by orbiting companion. This candidate object is estimated to be orbiting the parent star with a period of225.7±0.4 days at an eccentricity of0.3±0.1. Thesemi-major axis for thisKeplerian orbit is an estimated 0.6873 astronomical units. Because the inclination of the orbit remains unknown, the mass of this companion has not been determined. However, it can be constrained to have a mass of at least 21% the mass ofJupiter. There is no evidence of additional companions in the system.[2]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b / Ugarit | ≥0.198±0.018 MJ | 0.6875+0.0081 −0.0084 | 225.17+0.42 −0.52 | 0.270+0.100 −0.095 | — | — |
