Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Sagittarius |
Right ascension | 18h 31m 18.96122s[1] |
Declination | –18° 54′ 31.7326″[1] |
Apparent magnitude (V) | 6.81[2] |
Characteristics | |
Evolutionary stage | Main sequence |
Spectral type | K2V[3] |
U−B color index | +0.56[4] |
B−V color index | +0.861±0.007[2] |
Variable type | Suspected[5] |
Astrometry | |
Radial velocity (Rv) | −43.16±0.14[6] km/s |
Proper motion (μ) | RA: –138.402[1] mas/yr Dec.: –195.274[1] mas/yr |
Parallax (π) | 75.9773 ± 0.0458 mas[1] |
Distance | 42.93 ± 0.03 ly (13.162 ± 0.008 pc) |
Absolute magnitude (MV) | 6.20[2] |
Details | |
Mass | 0.79±0.11[7] M☉ |
Radius | 0.75+0.01 −0.04[1] R☉ |
Luminosity | 0.336±0.001[1] L☉ |
Surface gravity (log g) | 4.59[8] cgs |
Temperature | 5,133±37[8] K |
Metallicity [Fe/H] | –0.15[7] dex |
Rotational velocity (v sin i) | 4.2[8] km/s |
Age | 7.95[8] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
ARICNS | data |
HD 170657 is a star in the southern constellation Sagittarius. It is a suspected variable star that has been measured ranging in apparent visual magnitude from 6.82 down to 6.88,[5] which is dim enough to be a challenge to view with the naked eye even under ideal conditions. The star is located at a distance of 43 light years from the Sun based on parallax. It is drifting closer with a radial velocity of −43 km/s, and is predicted to come as close as 14.0 light-years in around 266,200 years.[6] The space velocity components of this star are (U, V, W) = (–41, –26, +6) km/s.[10]
This is a K-type main-sequence star with a stellar classification of K2V,[3] which indicates that, much like the Sun, it is generating energy at its core using hydrogen fusion. The star has 79%[7] of the mass of the Sun and 75%[1] of the Sun's radius. It is nearly eight[8] billion years old and is spinning with a projected rotational velocity of 4.2 [8] The star is radiating 33.6%[1] of the luminosity of the Sun from its photosphere at an effective temperature of 5,133 K.[8] When observed with the Spitzer Space Telescope, this star did not display an excess emission of infrared radiation, which may otherwise indicate the presence of an orbiting debris disk.[11]