| 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]
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