  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 11h 46m 03.01407s[1] |
| Declination | +47° 46′ 45.8553″[1] |
| Apparent magnitude (V) | 3.72[2] |
| Characteristics | |
| Evolutionary stage | Horizontal branch[3] |
| Spectral type | K0.5 IIIb[4] |
| U−Bcolor index | +1.16[2] |
| B−Vcolor index | +1.18[2] |
| Astrometry | |
| Radial velocity (Rv) | −9.02±0.20[2] km/s |
| Proper motion (μ) | RA: −138.297mas/yr[1] Dec.: +28.66mas/yr[1] |
| Parallax (π) | 16.438±0.113 mas[1] |
| Distance | 198 ± 1 ly (60.8 ± 0.4 pc) |
| Absolute magnitude (MV) | 0.10±0.02[5] |
| Details[2] | |
| Mass | 1.49[6] M☉ |
| Radius | 23.15±0.21[7] R☉ |
| Luminosity | 170.1±5.3[7] L☉ |
| Surface gravity (log g) | 2.2 cgs |
| Temperature | 4,331±33[7] K |
| Metallicity[Fe/H] | −0.44 dex |
| Rotational velocity (v sin i) | 2.3 km/s |
| Other designations | |
| Taiyangshou, Alkaphrah[8], Alkafzah[8],Chi UMa, χ UMa,63 Ursae Majoris,BD+48°1966,FK5 441,HD 102224,HIP 57399,HR 4518,SAO 43886[9] | |
| Database references | |
| SIMBAD | data |
Chi Ursae Majoris orχ Ursae Majoris, formally namedTaiyangshou/ˌtaɪˌjæŋˈʃoʊ/,[10] is a single[11]star in the northerncircumpolar constellation ofUrsa Major. The star has an orange hue and is visible to the naked eye at night with anapparent visual magnitude of 3.72.[2] It is located at a distance of approximately 198light-years from theSun based onparallax,[1] but is drifting closer with aradial velocity of −9 km/s.[2]
χ Ursae Majoris (Latinised toChi Ursae Majoris) is the star'sBayer designation.
It bore thetraditional nameTaiyangshou (太陽守,Pinyin: Tàiyángshǒu), meaningGuard of the Sun, fromChinese astronomy.[12] It is a single-starasterism in thePurple Forbidden enclosure (see:Chinese constellations). In R. H. Allen'sStar Names, this name was transliterated asTai Yang Show, "the Sun Governor".[13] The star has also been calledAlkafzah,Al Kaphrah, orEl Kophrah,[8][13] fromArabicالقفزةal-qafzah "the leap [of the gazelle]", which refers to an asterism consisting ofι,κ,λ,μ,ν, andξ Ursae Majoris.[12]
In 2016, the IAU organized aWorking Group on Star Names (WGSN)[14] to catalog and standardize proper names for stars. The WGSN approved the nameTaiyangshou for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names. The nameAlkaphrah was approved forκ Ursae Majoris.[10]
Chi Ursae Majoris is anevolved, orange huedK-typegiant with astellar classification of K0.5 IIIb.[4] It is ared clump giant,[3] which means it is on thehorizontal branch and is generating energy throughhelium fusion at its core. This star has expanded to 23[7] times theradius of the Sun with 1.49 times theSun's mass.[6] It is radiating 170 times the luminosity of the Sun from its enlargedphotosphere at aneffective temperature of 4,331 K.[7]
Thespiral galaxy in Ursa Major,NGC 3877 (= H I.201),type Sc, is best found from Chi Ursae Majoris, which is almost exactly 15arcminutes north of the galaxy.
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