  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 35m 21.38126s[1] |
| Declination | –00° 07′ 02.9888″[1] |
| Apparent magnitude (V) | 4.04[2] |
| Characteristics | |
| Spectral type | B9IV-Vn[3] or B8/9V[4] |
| U−Bcolor index | –0.28[5] |
| B−Vcolor index | –0.10[5] |
| Astrometry | |
| Radial velocity (Rv) | –8.0[2] km/s |
| Proper motion (μ) | RA: +89.74[1]mas/yr Dec.: –56.10[1]mas/yr |
| Parallax (π) | 19.43±0.25 mas[1] |
| Distance | 168 ± 2 ly (51.5 ± 0.7 pc) |
| Absolute magnitude (MV) | 0.31±0.15[6] |
| Details[6] | |
| Mass | 2.96±0.04 M☉ |
| Radius | 2.77±0.30 R☉ |
| Luminosity | 102.8 L☉ |
| Surface gravity (log g) | 4.02±0.04 cgs |
| Temperature | 11,042±301 K |
| Rotational velocity (v sin i) | 271±32 km/s |
| Age | 65[7] Myr |
| Other designations | |
| η Aqr, Eta Aqr,62 Aquarii,BD−00 4384,FK5 850,HD 213998,HIP 111497,HR 8597,SAO 146181[8] | |
| Database references | |
| SIMBAD | data |
Eta Aquarii,Latinized from η Aquarii, is theBayer designation for astar in theequatorialconstellation ofAquarius. It is visible to the naked eye with anapparent visual magnitude of 4.04.[2] The distance to this star, as determined byparallax measurements, is about 168light-years (52parsecs).[1] It is drifting closer to theSun with aradial velocity of –8 km/s.[2] Eta Aquarii is near the radiant of a meteor showernamed after it.
Thestellar classification of Eta Aquarii is B9IV-Vn,[3] which may indicate that it is beginning toevolve away from themain sequence into asubgiant as the supply of hydrogen at its core becomes exhausted. It is 65[7] million years old and is spinning rapidly with a highprojected rotational velocity of 271 km/s.[6] This rotation is causing an equatorial bulge, giving the star an oblate figure with a 24% larger radius at the equator than at the poles.[9] TheDoppler effect from the rapid rotation is causing theabsorption lines in the star'sspectrum to blur, as indicated by the 'n' suffix in the star's classification. Eta Aquarii has an estimated 2.96 times themass of the Sun and 2.8 times theSun's radius. The star is radiating 103 times theluminosity of the Sun from itsphotosphere at aneffective temperature of 11,042 K.[6]
This star, along withγ Aqr (Sadachbia),π Aqr (Seat) andζ Aqr (Sadaltager / Achr al Achbiya), wereal Aḣbiyah (الأخبية), the Tent.[10][11]
InChinese,墳墓 (Fén Mù), meaningTomb, refers to an asterism consisting of η Aquarii,γ Aquarii,ζ Aquarii,π Aquarii.[12] Consequently, theChinese name for η Aquarii itself is墳墓三 (Fén Mù sān, English:the Third Star of Tomb.)[13]
