In 1968, the "star" was identified by John Schmitt at the David Dunlap Observatory as a bright, variable radio source.

[2] In 1974, Oke and Gunn measured the redshift of BL Lacertae as z = 0.07, corresponding to a recession velocity of 21,000 km/s with respect to the Milky Way.

These characteristics are understood to result from relativistic beaming of emission from a jet of plasma ejected from the vicinity of a supermassive black hole.

BL Lacertae changes in apparent magnitude over fairly small time periods, typically between values of 14 and 17.

In January 2021, it exhibited extreme flaring behavior and was reported to reach magnitude 11.45 in the R filter band.