42 Draconis
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Draco |
| Right ascension | 18h 25m 59.13696s |
| Declination | +65° 33′ 48.5313″ |
| Apparent magnitude (V) | 4.82 |
| Characteristics | |
| Spectral type | K1.5 III |
| B−V color index | 1.18 |
| Astrometry | |
| Radial velocity (Rv) | 31.75±0.12 km/s |
| Proper motion (μ) | RA: +105.816 mas/yr Dec.: −26.846 mas/yr |
| Parallax (π) | 11.056±0.0841 mas |
| Distance | 295 ± 2 ly (90.4 ± 0.7 pc) |
| Absolute magnitude (MV) | −0.10 |
| Details | |
| Mass | 1.07±0.01 M☉ |
| Radius | 19.78±0.17 R☉ |
| Luminosity | 129.26+1.77 −1.05 L☉ |
| Surface gravity (log g) | 1.9±0.02 cgs |
| Temperature | 4,449+11 −17 K |
| Metallicity [Fe/H] | −0.43±0.01 dex |
| Rotation | 554±142 d (~479 or ~690 d) |
| Rotational velocity (v sin i) | 1.76±0.45 km/s |
| Age | 9.49±1.76 Gyr 13.19±1.92 Gyr |
| Other designations | |
| Fafnir, BD+65°1271, GC 25212, HD 170693, HIP 90344, HR 6945, SAO 17888, PPM 20916, GCRV 10941 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
42 Draconis (abbreviated 42 Dra), formally named Fafnir (/ˈfɑːvnər/ or /ˈfɑːfnɪər/), is a 5th magnitude K-type giant star located approximately 295 light-years away in the constellation of Draco. An exoplanet (designated 42 Draconis b, later named Orbitar) was once thought to be orbiting the star, but its existence has since been refuted.
Of spectral type K1.5III, the star has a mass similar to the Sun but with a radius 22 times greater. It is a metal-poor star with metallicity as low as 35% that of the Sun and its age is 9.49 billion years. It is the southern pole star of Venus.
A 2019 study using Gaia DR2 data found a companion star to 42 Draconis, about half the Sun's mass, at a separation of 24 arcseconds, corresponding to 2220 AU.