4 Lacertae

4 Lacertae is a single^[10] blue supergiant star in the northern constellation Lacerta, located about 2,600 light years away.^[1] This object visible to the naked eye as a white-hued star with an apparent visual magnitude of 4.55.^[2] It is moving closer to the Earth with a heliocentric radial velocity of −26 km/s.^[2] This star is a suspected member of the Lac OB1 association.^[3][5]

4 Lacertae

Observation data Epoch J2000      Equinox J2000
Constellation	Lacerta
Right ascension	22h 24m 30.99149s[1]
Declination	+49° 28′ 35.0106″[1]
Apparent magnitude (V)	4.55[2]
Characteristics
Evolutionary stage	Blue supergiant (blue loop)[3]
Spectral type	A0 Ib[4]
B−V color index	0.092±0.034[2]
Astrometry
Radial velocity (Rv)	−26.0±1.7[2] km/s
Proper motion (μ)	RA: −5.274(82)‍[1] mas/yr Dec.: −3.303(96)‍[1] mas/yr
Parallax (π)	1.2656±0.0891 mas[1]
Distance	2,600 ± 200 ly (790 ± 60 pc)
Absolute magnitude (MV)	−4.42[5]
Details
Mass	19+13 −8[6] M☉
Radius	59[6] R☉
Luminosity	62,000[6] L☉
Surface gravity (log g)	2.18[6] cgs
Temperature	11,800[6] K
Metallicity [Fe/H]	0.28±0.04[7] dex
Rotational velocity (v sin i)	28±3[6] km/s
Age	25.1±2.5[8] Myr
Other designations
4 Lac, BD+48°3715, HD 212593, HIP 110609, HR 8541, SAO 51970, 2MASS J22243097+4928351[9]
Database references
SIMBAD	data

This blue supergiant star has a stellar classification of A0 Ib.^[4] The surface abundances show evidence of material that has been processed via the CNO cycle at the core.^[3] It has ten^[8] times the mass of the Sun and has expanded to about 59^[6] times the Sun's radius. The star is around 25^[8] million years old and is spinning with a projected rotational velocity of 28 km/s.^[6][1] It is believed to be a blue loop star that has already spent time as a red supergiant after fusing the hydrogen within its core.