BL Lacertae

BL Lacertae or BL Lac is a highly variable, extragalactic AGN (active galactic nucleus or active galaxy). It was first discovered by Cuno Hoffmeister in 1929, but was originally thought to be an irregular variable star in the Milky Way galaxy and so was given a variable star designation. In 1968, the "star" was identified by John Schmitt at the David Dunlap Observatory as a bright, variable radio source. A faint trace of a host galaxy was also found. 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.

BL Lacertae is the original member of a type of blazar known as "BL Lacertae objects"; also termed simply "BL Lac objects". This class is distinguished by optical spectra devoid of the broad emission lines characteristic of quasars. On occasion, however, BL Lacertae has been observed to display weak emission lines.

BL Lacertae changes in apparent magnitude over fairly small time periods between values of 14 and 17. Its location in the sky for epoch 2000.0 is at RA 22h 02m 43.3s, DEC +42° 16′ 40″.

Other articles related to "bl, bl lacertae":

BL Lac
... BL Lac can mean two things BL Lacertae, an active galaxy, prototype of the BL Lacertae objects BL Lac object, a type of active galaxy, based on the prototype BL Lacertae galaxy ...
Lacerta - Notable Features - Deep-sky Objects
... BL Lacertae is the prototype of the BL Lacertae objects, which appear to be dim variable stars but are actually the variable nuclei of elliptical galaxies they are similar to quasars ... lent its name to a whole type of celestial objects, the BL Lacertae objects (a subtype of blazar) ...
BL Lac Object
... A BL Lacertae object or BL Lac object is a type of active galaxy with an active galactic nucleus (AGN) and is named after its prototype, BL Lacertae ... In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization ... Because of these properties, the prototype of the class (BL Lac) was originally believed to be a variable star ...
BL Lac Objects
... A BL Lacertae object or BL Lac object is a type of active galaxy with an active galactic nucleus (AGN) and is named after its prototype, BL Lacertae ... In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization ... Because of these properties, the prototype of the class (BL Lac) was originally believed to be a variable star ...