| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 25m 01.42751s[1] |
| Declination | −30° 45′ 23.6292″[1] |
| Apparent magnitude (V) | 5.58[2] |
| Characteristics | |
| Evolutionary stage | giant star |
| Spectral type | K0 III[3] |
| B−V color index | 1.138[4] |
| Astrometry | |
| Radial velocity (Rv) | −18.7±2.9[2] km/s |
| Proper motion (μ) | RA: −135.019[1] mas/yr Dec.: −70.932[1] mas/yr |
| Parallax (π) | 5.9260 ± 0.2434 mas[1] |
| Distance | 550 ± 20 ly (169 ± 7 pc) |
| Absolute magnitude (MV) | −0.93[4] |
| Details | |
| Radius | 8.9[5] R☉ |
| Luminosity | 309.45[2] L☉ |
| Surface gravity (log g) | 1.50[4] cgs |
| Temperature | 4,341[4] K |
| Metallicity [Fe/H] | −0.79[4] dex |
| Rotational velocity (v sin i) | 1.0[4] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
18 Sagittarii is a single[7] star in zodiac constellation of Sagittarius,[6] located around 550 light years away from the Sun based on parallax.[1] It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 5.58.[2] This object is moving closer to the Earth with a heliocentric radial velocity of −19 km/s.[2]
This is an aging giant star with a stellar classification of K0 III,[3] which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. It has expanded to about 9[5] times the Sun's radius and is radiating 309[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,341.[4] There is a much lower abundance of iron in the spectrum compared to the Sun.[4]
GaiaDR2 was invoked but never defined (see the help page).Anderson2012 was invoked but never defined (see the help page).houk1979 was invoked but never defined (see the help page).Randich1999 was invoked but never defined (see the help page).PasinettiFracassini2001 was invoked but never defined (see the help page).Simbad was invoked but never defined (see the help page).Eggleton2008 was invoked but never defined (see the help page).