Lacerta's brightest star, Alpha Lacertae, is only magnitude 3.77. One of the dimmest constellations, Lacerta is a modern figure invented in the 17th century to fill the relative blank area between Cygnus, Cassiopeia, and Andromeda.
Properties and Companion
Alpha Lacertae is a white class A1 V hydrogen-fusing main-sequence star. Just over 102 light years away, α Lac is what our brightest star, Sirius, would look like if it were a dozen times more distant. With a temperature of 9200 K, α Lac shines with a luminosity 27 times the Sun's; its radius is double solar. Unlike many class A stars, α Lac is chemically "normal," the result of a high rotation speed that keeps its atmosphere stirred up. Spinning at least 146 km/sec at the equator, the star makes a full rotation in under 17 hours. Containing just over twice the Sun's mass, α Lac is fairly young, and began its billion-year stable hydrogen-fusing lifetime not all that long ago.
At first glance, α Lac seems to have a companion, a magnitude 11.8 star located 36" away. The pairing is only line-of-sight; the two are separating much too quickly for their motion to be orbital, and the "companion" also shows a class A5 spectrum. To be that dim, it must have a distance of 2700 light years - 27 times farther than α Lac proper.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]