Psi2 Draconis
Star in the constellation Draco
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Psi2 Draconis is a solitary[9] giant star in the northern circumpolar constellation of Draco, also designated 34 Draconis. It lies just over a degree east of the brighter Psi1 Draconis.[10] Psi2 Draconis has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.45.[2] It is located at a distance of 940 light-years (287 parsecs) from the Sun based on parallax, but is drifting closer with a radial velocity of −2 km/s.[5]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Draco |
| Right ascension | 17h 55m 11.15296s[1] |
| Declination | +72° 00′ 18.4470″[1] |
| Apparent magnitude (V) | 5.45[2] |
| Characteristics | |
| Spectral type | F2 III+[3] or F3 II-III[4] |
| U−B color index | +0.15[2] |
| B−V color index | +0.30[2] |
| Astrometry | |
| Radial velocity (Rv) | −2.0[5] km/s |
| Proper motion (μ) | RA: +8.545[1] mas/yr Dec.: −2.133[1] mas/yr |
| Parallax (π) | 3.4888±0.0832 mas[1] |
| Distance | 930 ± 20 ly (287 ± 7 pc) |
| Absolute magnitude (MV) | −2.12±0.14[6] |
| Details[5] | |
| Mass | 2.02 M☉ |
| Radius | 14.70+0.64 −0.34[1] R☉ |
| Luminosity | 448±13[1] L☉ |
| Surface gravity (log g) | 2.32 cgs |
| Temperature | 6925+83 −152[1] K |
| Metallicity [Fe/H] | −1.29 dex |
| Rotational velocity (v sin i) | 50[7] km/s |
| Age | 800 Myr |
| Other designations | |
| ψ2 Dra, 34 Dra, BD+72°818, FK5 3429, HD 164613, HIP 87728, HR 6725, SAO 8961[8] | |
| Database references | |
| SIMBAD | data |
According to R. O. Gray and associates (2001), the stellar classification of Psi2 Draconis is F2III+;[3] a star that has used up its core hydrogen, cooled, and expanded away from the main sequence. A. P. Cowley and W. P. Bidelman (1979) found a similar class of F3 II-III, with the comment that the spectrum showed "many weak lines".[4] Based on the abundance of iron, the metallicity of this star is much lower than in the Sun. It is about 800[5] million years old and is spinning with a projected rotational velocity of 50 km/s.[7] The star has double[5] the mass of the Sun but has expanded to 15[1] times the Sun's radius. It is radiating 448[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 6,925 K.[1]