  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Leo |
| Right ascension | 10h 07m 54.2701s[1] |
| Declination | +09° 59′ 51.025″[1] |
| Apparent magnitude (V) | 4.39[2] |
| Characteristics | |
| Spectral type | K3.5 IIIb Fe-1:[3] |
| B−Vcolor index | 1.447[4] |
| Astrometry | |
| Radial velocity (Rv) | +39.84±0.20[5] km/s |
| Proper motion (μ) | RA: −82.021mas/yr[1] Dec.: −64.844mas/yr[1] |
| Parallax (π) | 11.0209±0.1661 mas[1] |
| Distance | 296 ± 4 ly (91 ± 1 pc)[1] |
| Absolute magnitude (MV) | −0.39[2] |
| Details | |
| Radius | 33.9+0.7 −0.71[6] R☉ |
| Luminosity | 283±9[6] L☉ |
| Surface gravity (log g) | 1.42[6] cgs |
| Temperature | 4066±28[6] K |
| Metallicity[Fe/H] | −0.02[7] dex |
| Rotational velocity (v sin i) | 5.1[4] km/s |
| Other designations | |
| Yunü,31 Leo,BD+10°2112,HD 87837,HIP 49637,HR 3980,SAO 98964[8] | |
| Database references | |
| SIMBAD | data |
31 Leonis, also namedYunü,[9] is abinary star[10] system in the equatorialconstellation ofLeo. The system is visible to the naked eye in unresolved form, having a combinedapparent visual magnitude of 4.39.[2] An estimated distance of around 300 light years is obtained from the annualparallax shift of 11.02 mas as seen from Earth's orbit.[1] At the current distance,interstellar extinction between Earth and 31 Leo diminished the apparent brightness by 0.12 magnitudes.[6] It is moving away from the Sun with aradial velocity of +39.8 km/s.[5]
The primary member of 31 Leonis, component A, is anevolvedK-typered giant[11] with astellar classification ofK3.5 IIIb Fe-1:,[3] where the suffix notation indicates an underabundance of iron in thespectrum. It has expanded to 34 times theSolar radius and is radiating around 283 times theSun's luminosity from itsphotosphere at aneffective temperature of 4,066 K.[6] The magnitude 13.6 secondary, component B, lies at anangular separation of 7.9 arcseconds, as of 2008.[10]
This star has the traditional Chinese name Yunü (御女); it is in the middle of the southernmost stars of the Xuanyuan (轩辕) constellation (ο Leonis andρ Leonis). TheIAU Working Group on Star Names approved the name Yunü for this star on 18 July 2024 and it is now so entered in the IAU Catalog of Star Names.[9]
