Eta Sagittae

η Sagittae
Location of η Sagittae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagitta
Right ascension 20h 05m 09.49303s[1]
Declination +19° 59′ 27.8575″[1]
Apparent magnitude (V) +5.09[2]
Characteristics
Spectral type K2 III[3]
U−B color index +0.98[2]
B−V color index +1.06[2]
Astrometry
Radial velocity (Rv)−40.53[4] km/s
Proper motion (μ) RA: +29.962±0.173[4] mas/yr
Dec.: +80.440±0.173[4] mas/yr
Parallax (π)20.9262 ± 0.1208 mas[4]
Distance155.9 ± 0.9 ly
(47.8 ± 0.3 pc)
Absolute magnitude (MV)1.61[5]
Details[6]
Mass1.73±0.09 M☉
Radius7.08±0.21 R☉
Luminosity26 L☉
Surface gravity (log g)3.03±0.10 cgs
Temperature4,784±3.03 K
Metallicity [Fe/H]+0.10 dex
Rotational velocity (v sin i)1.3[5] km/s
Age1.69±0.25 Gyr
Other designations
η Sge, 16 Sge, BD+19°4277, FK5 3609, GC 27868, HD 190608, HIP 98920, HR 7679, SAO 105659, PPM 137588[7]
Database references
SIMBADdata

Eta Sagittae (η Sagittae) is solitary[8] star in the northern constellation of Sagitta. It is faintly visible to the naked eye, having an apparent visual magnitude of +5.09.[2] Based upon an annual parallax shift of 20.34 mas,[1] it is approximately 160 light years distant from the Sun. There is a 61.1% chance that it is a member of the Hyades-Pleiades stream of stars that share a common motion through space.[9]

This is an evolved K-type giant star with a stellar classification of K2 III.[3] At the age of about 1.7 billion years,[6] it is now a red clump star that is generating energy through the fusion of helium at its core.[10] Eta Sagittae has 1.7 times the mass of the Sun and has expanded to seven times the Sun's radius. It is radiating 25.7 times the Sun's luminosity from its photosphere at an effective temperature of 4,784 K.[6]

  1. ^ a b c Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Argue1966 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Roman1952 was invoked but never defined (see the help page).
  4. ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  5. ^ a b Cite error: The named reference Setaiwan2004 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Villaver2013 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Famaey2005 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Alves2000 was invoked but never defined (see the help page).