10 Lacertae (10 Lac) is a star in the constellation Lacerta. With an apparent magnitude is 4.9, it is located around 700 parsecs (2,300 ly) distant in the small Lacerta OB1 association. It is a hot blue main-sequence star of spectral type O9V, a massive star that is currently fusing its core hydrogen. It is a suspected Beta Cephei variable star.
10 Lacertae was one of the first O-type stars (along with S Monocerotis) to be defined as an anchor point for the MKK spectral classification; since the early twentieth century it has served as such a point. Specifically, the star is representative of O9V stars, meaning relatively cool O-type stars on the main-sequence.
10 Lacertae has an 8th magnitude companion about one arc-minute away.
Epoch J2000 Equinox J2000
|Right ascension||22h 39m 15.67864s|
|Declination||+39° 03′ 00.9712″|
|Apparent magnitude (V)||4.880|
|U−B color index||−1.010|
|B−V color index||−0.210|
|Variable type||β Cep?|
|Radial velocity (Rv)||−10.10 km/s|
|Proper motion (μ)||RA: −0.32 mas/yr
Dec.: −5.46 mas/yr
|Parallax (π)||1.89 ± 0.22 mas|
|Absolute magnitude (MV)||−4.40|
|Surface gravity (log g)||4.03 cgs|
|Rotational velocity (v sin i)||35 km/s|