BL Lacertae objects are radio galaxies characterized by rapidly varying luminosity, no emission lines in the spectrum, and point-like appearance. As with blazars, they are aligned so that their plasma jets point in our direction.
BL Lacertae objects (NASA Thesaurus) One of a class of astronomical objects exhibiting; (1) rapid variations in intensity at radio, infrared, and optical wavelengths; (2) energy distributions largely at infrared wavelengths; ...
Handbook of Quasistellar and BL Lacertae Objects, E.R. Craine 1977, Pachart, Tucson. Finding charts, fluxes, positions, references; much less necessary now than it was before the Web.
As well, W Com was originally identified as a variable star and so given a variable star designation, but later discovered to be a BL Lacertae object. It is normally around magnitude 16.5m, but has been known to reach 12th magnitude.
Discovering and investigating the various properties of QSOs and active galaxies such as radio galaxies, Seyfert galaxies, and BL Lacertae objects objects over the past three decades, ...
However, blazars are not a homogeneous group and can be divided into two: highly variable quasars, sometimes called Optically Violently Variable (OVV) quasars (these are a small subset of all quasars) and BL Lacertae objects ("BL Lac objects" or ...
A third type of active galaxy called BL Lacertae objects (BL Lac objects for short) are probably radio galaxies with their jets pointed right at us. The energy from BL Lac objects varies very quickly and erratically.
Active Galaxy - A galaxy whose nucleus is unusually bright and small. Seyfert galaxies, BL Lacertae objects, and quasars are examples of active galaxies ...
red shifts identify them as objects at very large distances. Most astronomers now believe that quasars are active galaxies whose nucleii contain enormous black holes. They are probably closely related to radio galaxies and to BL Lacertae Objects.
 See also: Lacerta, Emission, Galaxies, Quasar, Luminosity
  
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