BL Lacertae

BL Lac is a variable active galactic nucleus and prototype known as BL Lacertae objects class of active galactic nuclei.

BL Lacertae ( BL Lac briefly ) in 1929 classified by Cuno Hoffmeister because of its varying brightness and star-like compactness as a variable star and later named as usual with a letter code and the name of the constellation.

1968 this object by JL Schmitt was identified with a radio source and found a faint mist -like outer object. In a recorded 1973 spectrum of this object surrounding Oke and Gunn absorption lines were able to determine it as a galaxy at a redshift z = 0:07 and thus identified a distance of about 900 million light years. BL Lac is therefore not a star, but an active galactic nucleus to which it belongs as a prototype of the BL Lac objects known as blazars today a subset of quasars. In BL Lac objects, the core appears to be particularly bright to us by a directed beam of matter (Jet) and outshines the surrounding galaxy so strong that it is difficult or impossible to study with today's methods.

The brightness of BL Lac varies between about 14 and 17 magnitude. The position in the sky is 22h02m43.3s RA, DEC 42 ° 16'40 " ( J2000.0 ).