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Theta Lyrae (θ Lyr) is a star in a trinary star system, in the constellation Lyra, approximately 770 light years away from Earth. Theta Lyrae is an orange bright giant star of the spectral type K0II, which means that it possesses a surface temperature of about 5,000 kelvins, and is many times bigger and brighter, yet cooler, than the Sun.[3]

Theta Lyrae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Lyra
Right ascension 19h 16m 22.0951s / 19h 16m 30.069s / 19h 16m 28.7s
Declination +38° 8' 1.431" / +38° 8' 35.80" / +38° 7' 1"
Apparent magnitude (V) 4.347 / 9.5 / 11.0
Characteristics
Spectral type K0II[1] + K2III + ?
U−B color index +1.23
B−V color index +1.25
Astrometry
Radial velocity (Rv)-30.9 km/s
Proper motion (μ) RA: -0.49 mas/yr
Dec.: 1.23 / 14.0 mas/yr
Parallax (π)4.24 ± 0.49 mas
Distanceapprox. 770 ly
(approx. 240 pc)
Absolute magnitude (MV)−2.76+0.27
−0.24[1]
Details
θ Lyr
Radius57±7[2] R☉
Surface gravity (log g)1.93[1] cgs
Temperature4500[1] K
Metallicity [Fe/H]−0.01[1] dex
Rotational velocity (v sin i)3.6±1.4[1] km/s
Other designations
θ Lyrae, 21 Lyrae, HR 7314, BD+37°3398, HD 180809, SAO 68065, HIP 94713, GC 26585, IDS 19129+3757, GSC 03121-02287, BD +37°3399, BD +37°3399B[3][4][5]
Database references
SIMBADdata

It is orbited by a subsystem composed of BD+37° 3399 and BD+37° 3399B. 10th magnitude BD+37° 3399 is a giant star with a spectral type of K2III. It is therefore almost the same temperature as Theta Lyrae, but smaller and dimmer.[4] BD+37° 3399B is an 11th magnitude star of an unknown spectral type.[5]


References


  1. Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal, 135 (3): 892–906, arXiv:0711.4984, Bibcode:2008AJ....135..892C, doi:10.1088/0004-6256/135/3/892, S2CID 2756572
  2. Nordgren, Tyler E.; et al. (December 1999), "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal, 118 (6): 3032–3038, Bibcode:1999AJ....118.3032N, doi:10.1086/301114
  3. "* tet Lyr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 15, 2007.
  4. "BD+37 3399". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 15, 2007.
  5. "Simbad Query Result". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 15, 2007.


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