Eta Aquarii

Eta Aquarii
Location of η Aquarii (circled)
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−B color index –0.28[5]
B−V color 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]
Distance168 ± 2 ly
(51.5 ± 0.7 pc)
Absolute magnitude (MV)0.31±0.15[6]
Details[6]
Mass2.96±0.04 M☉
Radius2.77±0.30 R☉
Luminosity102.8 L☉
Surface gravity (log g)4.02±0.04 cgs
Temperature11,042±301 K
Rotational velocity (v sin i)271±32 km/s
Age65[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
SIMBADdata

Eta Aquarii, Latinized from η Aquarii, is the Bayer designation for a star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.04.[2] The distance to this star, as determined by parallax measurements, is about 168 light-years (52 parsecs).[1] It is drifting closer to the Sun with a radial velocity of –8 km/s.[2] Eta Aquarii is near the radiant of a meteor shower named after it.

The stellar classification of Eta Aquarii is B9IV-Vn,[3] which may indicate that it is beginning to evolve away from the main sequence into a subgiant as the supply of hydrogen at its core becomes exhausted. It is 65[7] million years old and is spinning rapidly with a high projected 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] The Doppler effect from the rapid rotation is causing the absorption lines in the star's spectrum to blur, as indicated by the 'n' suffix in the star's classification. Eta Aquarii has an estimated 2.96 times the mass of the Sun and 2.8 times the Sun's radius. The star is radiating 103 times the luminosity of the Sun from its photosphere at an effective temperature of 11,042 K.[6]

  1. ^ a b c d e f Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference scfs was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference aj77_750 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Houk1999 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference clpl4_99 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference Cochetti_et_al_2020 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference David_Hillenbrand_2015 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference aar20_1_51 was invoked but never defined (see the help page).