18 Scorpii
 Location of 18 Scorpii (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 15m 37.26946s |
| Declination | –08° 22′ 09.9870″ |
| Apparent magnitude (V) | 5.503 |
| Characteristics | |
| Spectral type | G2 Va |
| U−B color index | +0.18 |
| B−V color index | +0.64 |
| Variable type | Sun-like |
| Astrometry | |
| Radial velocity (Rv) | +11.6 km/s |
| Proper motion (μ) |
RA: 230.77 mas/yr Dec.: -495.53 mas/yr |
| Parallax (π) | 71.94 ± 0.37mas |
| Distance | 45.3 ± 0.2 ly (13.90 ± 0.07 pc) |
| Absolute magnitude (MV) | 4.77 |
| Details | |
| Mass | 1.02 ± 0.03 M☉ |
| Radius | 1.010 ± 0.009 R☉ |
| Luminosity | 1.058 ± 0.028 L☉ |
| Surface gravity (log g) | 4.45 cgs |
| Temperature | 5,433 ± 69 K |
| Metallicity [Fe/H] | 0.04 dex |
| Rotation | 22.7 ± 0.5 |
| Age | 2.9±0.5 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
18 Scorpii is a solitary star located at a distance of some 45.3 light-years (13.9 parsecs) from Earth at the northern edge of the Scorpius constellation. It has an apparent visual magnitude of 5.5, which is bright enough to be seen with the naked eye outside of urban areas.
18 Scorpii has some physical properties in common with the Sun, a G-type star. Cayrel de Strobel (1996) included it in her review of the stars most similar to the Sun, and Porto de Mello & da Silva (1997) identified it as a younger solar twin. Some scientists therefore believe the prospects for life in its vicinity are good. However, no planet has yet been discovered orbiting this star.
18 Scorpii is a main sequence star of spectral and luminosity type G2 Va, with the luminosity class of 'V' indicating it is generating energy through the nuclear fusion of hydrogen in its core region. Sousa et al. (2008) found its metallicity to be about 1.1 times that of the Sun, which means the abundance of elements other than hydrogen or helium is 10% greater. The radius of this star, as measured using interferometry by Bazot et al. (2011), is 101% the radius of the Sun. When combined with the results of asteroseismology measurements, this allows the mass of the star to be estimated as 102% of the Sun's mass. This star is radiating 106% of the Sun's luminosity from its outer atmosphere at an effective temperature of 5,433 K. It is this heat that gives the star the yellow-hued glow of a G-type star.
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