  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aries |
| Right ascension | 02h 47m 54.54142s[1] |
| Declination | +29° 14′ 49.6132″[1] |
| Apparent magnitude (V) | 4.514[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | K1.5 III[4] |
| U−Bcolor index | +1.083[2] |
| B−Vcolor index | +1.118[2] |
| R−Icolor index | 0.58 |
| Astrometry | |
| Radial velocity (Rv) | −15.53±0.14[5] km/s |
| Proper motion (μ) | RA: +149.47±0.25[1]mas/yr Dec.: −127.05±0.18[1]mas/yr |
| Parallax (π) | 19.01±0.21 mas[1] |
| Distance | 172 ± 2 ly (52.6 ± 0.6 pc) |
| Details | |
| Mass | 1.6[3] M☉ |
| Radius | 10.22±0.72[6] R☉ |
| Luminosity | 48.7±0.7[6] L☉ |
| Surface gravity (log g) | 2.7[5] cgs |
| Temperature | 4,768±167[6] K |
| Metallicity[Fe/H] | −0.02[5] dex |
| Rotational velocity (v sin i) | 4.5[5] km/s |
| Other designations | |
| Lilii Borea,BD+28°462,HD 17361,HIP 13061,HR 824,SAO 75578.[7] | |
| Database references | |
| SIMBAD | data |
39 Arietis, officially namedLilii Borea/ˈlɪliaɪˈbɔːriə/,[8] is astar in the northernconstellation ofAries. It is visible to the naked eye with anapparent visual magnitude of +4.5.[2] The distance to this star, as determined from an annualparallax shift of 19.01 mas,[1] is approximately 172light-years (53parsecs).This star was formerly located in the obsolete constellationMusca Borealis.
39 Arietis (abbreviated39 Ari) is the star'sFlamsteed designation.
This star was described asLilii Borea byNicolas-Louis de Lacaille in 1757,[9][10] as a star of the now-defunct constellation ofLilium (theLily). The words are simply the Latin phraseLīliī Boreā 'in the north of Lilium'.Līliī Austrīnā/ɔːˈstraɪnə/ 'in the south of Lilium' was41 Arietis.
In 2016, theInternational Astronomical Union organized aWorking Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN approved the nameLilii Borea for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[8]
InChinese,胃宿 (Wèi Su), meaningStomach, refers to anasterism consisting of 39 Arietis,35 Arietis and41 Arietis.[12] Consequently, theChinese name for 39 Arietis itself is胃宿二 (Wèi Su èr, English:the Second Star of Stomach).[13]
39 Arietis is agiant star with astellar classification of K1.5 III.[4] It is currently at anevolutionary stage known as thered clump, indicating that it is generating energy through the fusion ofhelium at its core.[3] It has 1.6[3] times themass of the Sun, but its outer envelope has expanded to around 10 times theSun's radius. It shines with 49 times theluminosity of the Sun. This energy is being radiated into outer space from itsouter atmosphere at aneffective temperature of 4,768 K,[6] giving it the cool orange-hued glow of aK-type star.[14]
