BL Lacertae or BL Lac is a highly variable, extragalactic active galactic nucleus (AGN or active galaxy). It was first discovered by Cuno Hoffmeister in 1929,[1] 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.[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.[3] The redshift figure implies that the object lies at a distance of 900 million light years.
A visual band light curve for BL Lacertae, plotted from AAVSO data[4]
Due to its early discovery, BL Lacertae became the prototype and namesake of the class of active galactic nuclei known as "BL Lacertae objects" or "BL Lac objects". This class is distinguished by rapid and high-amplitude brightness variations and by optical spectra devoid (or nearly devoid) of the broad emission lines characteristic of quasars. 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 Lac objects are also categorized as a type of blazar.
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.[5]
^Schmitt, John L. (May 1968). "BL Lac identified as a Radio Source". Nature. 218 (5142): 663. Bibcode:1968Natur.218..663S. doi:10.1038/218663a0. S2CID 4213061.
^Oke, J. B.; Gunn, J. E. (1974). "The Distance of BL Lacertae". Astrophysical Journal Letters. 189: 5. Bibcode:1974ApJ...189L...5O. doi:10.1086/181450.
^Cite error: The named reference aavso was invoked but never defined (see the help page).
^Bonnoli, Giacomo. "ATel #14329". The Astronomer's Telegram. Retrieved 20 January 2021.
BLLacertae or BL Lac is a highly variable, extragalactic active galactic nucleus (AGN or active galaxy). It was first discovered by Cuno Hoffmeister...
BL Lac may refer to: BLLacertae, an active galaxy, prototype of the BLLacertae objects BLLacertae object, a type of active galaxy, based on the prototype...
class of galaxy: BLLacertae-type objects. This terminology was soon shortened to "BLLacertae object", "BL Lac object" or simply "BL Lac". (The latter...
stars. It also contains the prototypic blazar BLLacertae. Lacerta contains no Messier objects. Alpha Lacertae is a blue-white hued main-sequence star of...
a BLLacertae object (of lower luminosity than its surrounds) seen from a relatively large angle. Flux variations, characteristic of the BLLacertae objects...
C.; Dressel, Linda L.; Harms, Richard J. (1998). "M87: A Misaligned BLLacertae Object?". The Astrophysical Journal. 493 (2): L83–L86. arXiv:astro-ph/9711241...
OJ 287 is a BL Lac object 5 billion light-years from Earth that has produced quasi-periodic optical outbursts going back approximately 120 years, as first...
(though still too faint to see with the naked eye); and PKS 2155-304, a BLLacertae object that is one of the optically brightest blazars in the sky. Pisces...
in the constellation Ursa Major. The object is an active galaxy and a BLLacertae object, and is a strong source of gamma rays. It is about 397 million...
a spectrum extending to the highest energy gamma rays. It is a blazar or BL Lac object, which is an active galactic nucleus with a jet that is shooting...
AP Librae is a BLLacertae object located at a distance of 700 million light years in the southern constellation of Libra. In the visual band it is one...
January 2020. Miller, J. S. (December 1981), "The galaxy components of BLLacertae objects, N systems, and quasi-stellar objects.", Publications of the...
spectral line widths BLLAC – (celestial object) BLLACertae, a class of active galaxies for which BLLacertae is the archetypal object also BLL BLAST – (telescope)...
northwest, was originally designated a variable star and later found to be a BLLacertae object. As of 2009, it had the most intense gamma ray spectrum of the...
3C 66A is a blazar located in the constellation Andromeda. The "distance" of a far away galaxy depends on the distance measurement used. With a redshift...
Bibcode:1968ApJ...151L..79U. doi:10.1086/180147. Wikisky image of 3C 371 New X-ray Jet in Nearby BLLacertae Object 3C371 (Brandeis University Radio Astronomy)...
2008: discovery of the first blazar of the intermediate frequency peaked BLLacertae (IBL) type at very high energies, W Comae followed by a second IBL 3C...
been targets of WEBT campaigns: AO 0235+16 Markarian 421 S5 0716+71 BLLacertae Markarian 501 3C 66A OJ 287 3C 454.3 3C 279 After eighteen years of operations...
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