  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda[1] |
| Right ascension | 01h 37m 59.56074s[2] |
| Declination | +48° 37′ 41.5798″[2] |
| Apparent magnitude (V) | 3.57[3] |
| Characteristics | |
| Spectral type | K3- III CN0.5[4] |
| U−Bcolor index | +1.44[3] |
| B−Vcolor index | +1.28[3] |
| Astrometry | |
| Radial velocity (Rv) | 18.41[5] km/s |
| Proper motion (μ) | RA: +61.334[2]mas/yr Dec.: -113.100[2]mas/yr |
| Parallax (π) | 19.2489±0.4077 mas[2] |
| Distance | 169 ± 4 ly (52 ± 1 pc) |
| Absolute magnitude (MV) | −0.04[6] |
| Details[7] | |
| Mass | 1.75±0.15 M☉ |
| Radius | 21.30±0.21 R☉ |
| Luminosity | 142.1±7.6 L☉ |
| Surface gravity (log g) | 2.01 cgs |
| Temperature | 4,316±54 K |
| Metallicity[Fe/H] | 0.07 dex |
| Age | 1.70±0.40 Gyr |
| Other designations | |
| υ Per,51 And,BD+47°467,HD 9927,HIP 7607,HR 464,SAO 37375,PPM 44238[8] | |
| Database references | |
| SIMBAD | data |
51 Andromedae, abbreviated51 And and formally namedNembus/ˈnɛmbəs/,[9] is the 5th brighteststar in the northernconstellation ofAndromeda, very slightly dimmer than theAndromeda Galaxy also being of 4thmagnitude. It is an orangeK-typegiant star with anapparent magnitude of +3.57 and is about 169light-years from theEarth/solar system. It is traditionally depicted as one of the two northern, far upper ends of the mythological, chained-to-the-rocks princess, the other being binary star systemGamma Andromedae.
At an estimated age of 1.7 billion years, this is anevolvedred giant star with astellar classification ofK3- III CN0.5.[4] The suffix notation indicates a mild enhancement ofcyanogenabsorption lines in itsspectrum. This star has 1.8 times themass of the Sun and it has expanded to 21.3 times theSun's radius. It is radiating 142 times theSun's luminosity from its enlargedphotosphere at aneffective temperature of 4,951 K.[7]
51 Andromedae is the star'sFlamsteed designation.Ptolemy included this star in Andromeda in theAlmagest. It was for a time moved into the greater form of Perseus envisioned byJohann Bayer asUpsilon Persei.Flamsteed oversaw its constellation reverting and theInternational Astronomical Union (IAU) made his51 Andromedae its official designation in 1930.[10][11][12]
The star bore the nameNembus, of undetermined origin and meaning,[13] in Bayer'sUranometria (1603)[14] andBode'sstar atlasUranographia (1801).[15] In 2016, the IAU organized aWorking Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. The WGSN approved the nameNembus for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[9]
InChinese,天大將軍 (Tiān Dà Jiāng Jūn), meaningHeaven's Great General, refers to anasterism consisting of 51 Andromedae,Gamma Andromedae,Phi Persei,49 Andromedae,Chi Andromedae,Upsilon Andromedae,Tau Andromedae,56 Andromedae,Beta Trianguli,Gamma Trianguli andDelta Trianguli.[17] Consequently, theChinese name for 51 Andromedae itself is天大將軍三 (Tiān Dà Jiāng Jūn sān, English:the Third Star of Heaven's Great General.)[citation needed]
