Theta Lyrae

Theta Lyrae (θ Lyr) is a red giant star in the constellation Lyra, approximately 760 light years away from Earth.

Theta Lyrae

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Lyra
Right ascension	19h 16m 22.0951s[1]
Declination	+38° 08′ 01.431″[1]
Apparent magnitude (V)	4.38[2]
Characteristics
Spectral type	K0II[3]
U−B color index	+1.23[2]
B−V color index	+1.26[2]
Astrometry
Radial velocity (Rv)	−31.05±0.14[1] km/s
Proper motion (μ)	RA: −2.864 mas/yr[1] Dec.: 4.114 mas/yr[1]
Parallax (π)	4.2005±0.1053 mas[1]
Distance	755.9+21.9 −20.2 ly (237.9+6.7 −6.2 pc)[4]
Absolute magnitude (MV)	−2.76+0.27 −0.24[3]
Details
Radius	60.31+1.92 −2.99[5] R☉
Luminosity	1,374±43[5] L☉
Surface gravity (log g)	1.93[3] cgs
Temperature	4,523±44[5] K
Metallicity [Fe/H]	−0.01[3] dex
Rotational velocity (v sin i)	3.6±1.4[3] 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[6]
Database references
SIMBAD	data

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 K, and is many times bigger and brighter, yet cooler, than the Sun.

BD+37°3399 and BD+37°3399B are respectively 10th- and 11th-magnitude companions, although not at the same distance. BD+37°3399 is a giant star with a spectral type of K2III. It is therefore almost the same temperature as Theta Lyrae.^[7] BD+37° 3399B is an 11th magnitude star of an unknown spectral type.^[8]