Eta Herculis
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| 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 mas[3] |
| Distance | 112 ± 2 ly (34.4 ± 0.6 pc) |
| Absolute magnitude (MV) | +0.84[4] |
| Details | |
| Mass | 2.13[4] M☉ |
| Radius | 11.55+0.19 −0.20[5] R☉ |
| Luminosity | 50[6] L☉ |
| Temperature | 4,900[6] K |
| Metallicity [Fe/H] | -0.28[7] dex |
| Rotational velocity (v sin i) | 8[8] km/s |
| Age | 1[6] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Herculis (η Her, η Herculis) is a fourth-magnitude star in the constellation Hercules.
Properties
[edit]Eta Herculis is a G-type star. With a stellar classification G7.5IIIb, it is considerably larger than the Sun, having a mass that is 2.3 times solar and a radius 9.8 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 50 times more luminous than the Sun.[6] 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.[6]
References
[edit]- ^ a b c d e f g "* eta Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-06-09.
- ^ a b 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.
- ^ a b Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; et al. (July 1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
- ^ a b 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
- ^ 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, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, S2CID 119427037.
- ^ a b c d e f Kaler, James B. "ETA HER (Eta Herculis)". Stars. University of Illinois. Retrieved 2010-06-09.
- ^ Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. (2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics. 480 (1): 91–101. arXiv:0712.1370. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788. S2CID 16602121.
- ^ Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239. Bibcode:1970CoAsi.239....1B.
External links
[edit]- Jim Kaler's Stars:Eta Herculis
