| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pisces |
| Right ascension | 23h 03m 08.20704s[1] |
| Declination | −00° 25′ 46.6777″[1] |
| Apparent magnitude (V) | 7.78[2] |
| Characteristics | |
| Spectral type | F8V[3] |
| B−Vcolor index | 0.578±0.004[2] |
| Astrometry | |
| Radial velocity (Rv) | +10.00±0.02[2] km/s |
| Proper motion (μ) | RA: −89.933[1]mas/yr Dec.: −168.781[1]mas/yr |
| Parallax (π) | 17.9946±0.0793 mas[1] |
| Distance | 181.3 ± 0.8 ly (55.6 ± 0.2 pc) |
| Absolute magnitude (MV) | 4.09[2] +11.02±0.13[4] |
| Details[5] | |
| A | |
| Mass | 1.02 M☉ |
| Radius | 1.32±0.06 R☉ |
| Luminosity | 1.93±0.04[6] L☉ |
| Surface gravity (log g) | 4.13±0.02 cgs |
| Temperature | 5,882±8[7] K |
| Metallicity | −0.19±0.01 |
| Rotational velocity (v sin i) | 1.18±0.05 km/s |
| Age | 9.40±0.22 Gyr |
| HD 217786 B | |
| Mass | 0.1622+0.0071 −0.0068[4] M☉ |
| Other designations | |
| BD−01°4382,Gaia DR2 2650902026099857920,HD 217786,HIP 113834,TYC 5242-591-1,GSC 05242-00591,2MASS J23030822-0025465[8] | |
| Database references | |
| SIMBAD | data |
HD 217786 is abinary star[4] system in theequatorialconstellation ofPisces. With anapparent visual magnitude of 7.78,[2] it requires binoculars or a small telescope to view. The system is located at a distance of181 light-years from theSun based onparallax, and is drifting further away with aradial velocity of +10 km/s.[2] Kinematically, the star system belongs to thethin disk population of theMilky Way.[7]
The primary is anF-type main-sequence star with astellar classification of F8V. It is much older than Sun with an estimated age of 9.4 billion years and is spinning slowly with aprojected rotational velocity of 1.2 km/s. The star has a lower proportion of heavy elements than the Sun, having 65% of solar abundance.[7] It has about the same mass as the Sun but a 32% larger radius.[5] The star is radiating nearly double[6] the luminosity of the Sun from itsphotosphere at aneffective temperature of 5,882 K.[7]
A low-mass stellar companion at a projected separation of 155AU was discovered in 2016.[4] Theproper motion of this co-moving object suggests it is gravitationally-bound to the primary, and their orbit is being viewed edge-on. If the orbit is assumed to be circular, then theorbital period for the pair is ~6.2 Myr.[4] No other companion stars have been detected at separations from 2.74 to 76.80AUs.[6]
The star system exhibits strongstellar flare activity in the ultraviolet.[9]
In 2010 onesuperjovian planet orbrown dwarf on an eccentric orbit was discovered utilising theradial velocity method.[10] Designated component Ab, the high eccentricity of this object may have been caused by interaction with the secondary star.[4] In 2022, the inclination and true mass of HD 217786 Ab were measured viaastrometry, and a second planet was discovered orbiting closer to the star.[11]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| c | ≥0.023±0.002 MJ | 0.038±0.002 | 2.5+0.00010 −0.00005 | — | — | — |
| b | 13.852+1.267 −1.311 MJ | 2.446+0.109 −0.119 | 1,301.4+1.2 −0.5 | 0.311+0.002 −0.003 | 69.767+0.601 −0.386° | — |
