Astronomy:Eta Herculis

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Short description: Star in the constellation Hercules
Eta Herculis
Location of η Herculis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Hercules
Right ascension  16h 42m 53.7653s[1]
Declination +38° 55′ 20.116″[1]
Apparent magnitude (V) 3.487[1]
Characteristics
Spectral type G7.5 IIIb[1]
U−B color index +0.61[2]
B−V color index +0.92[2]
Astrometry
Radial velocity (Rv)+8.3[1] km/s
Proper motion (μ) RA: +35.58[1] mas/yr
Dec.: −84.98[1] mas/yr
Parallax (π)29.11 ± 0.52[3] mas
Distance112 ± 2 ly
(34.4 ± 0.6 pc)
Absolute magnitude (MV)+0.84[4]
Details
Mass2.01±0.11[5] M☉
Radius9.28±0.05[6] R☉
Luminosity45.8±2.3[5] L☉
Temperature5,025±65[5] K
Metallicity [Fe/H]−0.198[7] dex
Rotational velocity (v sin i)8[8] km/s
Age1.08±0.18[5] Gyr
Other designations
η Her, 44 Her, BD+39 3029, FK5 626, GC 22502, GJ 636, HD 150997, HIP 81833, HR 6220, SAO 65504, CCDM J16428+3855A[1]
Database references
SIMBADdata

Eta Herculis (η Her, η Herculis) is a third-magnitude star in the constellation Hercules. It is located at 110 light-years from Earth.[7]

Properties

Eta Herculis is a G-type giant star. With a stellar classification G7.5IIIb, it is considerably larger and more evolved than the Sun, having a mass that is two times solar[5] and a radius 9.3 times.[6] Though it only shines with an apparent magnitude of 3.48, it is part of the "Keystone" asterism, visible overhead in the mid-summer night sky to northern observers, allowing it to be easily recognized. Eta Herculis is 46 times more luminous than the Sun.[5] The Hipparcos satellite mission estimated its distance at roughly 34.4 parsecs[3] from Earth, or 112 light years away.

If one follows the line connecting Eta Herculis with Zeta Herculis one comes across one of the earliest and most stunning globular clusters in the nighttime sky, M13, discovered in 1714 by Edmond Halley.

Eta Herculis is a double star once thought to be part of a binary star system.[9]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 "* eta Her". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+eta+Her. 
  2. ↑ 2.0 2.1 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues 2237. Bibcode: 2002yCat.2237....0D. 
  3. ↑ 3.0 3.1 Perryman, M. A. C. et al. (July 1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics 323: L49–L52. Bibcode: 1997A&A...323L..49P. 
  4. ↑ Pizzolato, N.; Maggio, A.; Sciortino, S. (September 2000). "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases". Astronomy and Astrophysics 361: 614–628. Bibcode: 2000A&A...361..614P. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 Baines, Ellyn K.; Armstrong, J. Thomas; Schmitt, Henrique R.; Zavala, R. T.; Benson, James A.; Hutter, Donald J.; Tycner, Christopher; Van Belle, Gerard T. (2018). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal 155 (1): 30. doi:10.3847/1538-3881/aa9d8b. Bibcode: 2018AJ....155...30B. 
  6. ↑ 6.0 6.1 Anugu, Narsireddy; Monnier, John D.; Mérand, Antoine; Flores, Becky; Gallenne, Alexandre; Gies, Douglas R.; Gutierrez, Mayra; Klement, Robert et al. (2026-07-27). "Empirical H- and K-band Limb Darkening for 31 CHARA Stars: A Near-Infrared Benchmark for Stellar-Atmosphere Models". The Astronomical Journal. 
  7. ↑ 7.0 7.1 Gray, David F.; Kaur, Taranpreet (November 2019). "A Recipe for Finding Stellar Radii, Temperatures, Surface Gravities, Metallicities, and Masses Using Spectral Lines" (in en). The Astrophysical Journal 882 (2): 148. doi:10.3847/1538-4357/ab2fce. ISSN 0004-637X. Bibcode: 2019ApJ...882..148G. 
  8. ↑ Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities.". Contributi Osservatorio Astronomico di Padova in Asiago 239: 1. Bibcode: 1970CoAsi.239....1B. 
  9. ↑ Kaler, James B.. "ETA HER (Eta Herculis)". Stars. University of Illinois. http://stars.astro.illinois.edu/sow/etaher.html. 

Coordinates: Sky map 16h 42m 53.80s, +38° 55′ 20.116″



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