4 relations: Active galactic nucleus, BL Lacertae, BL Lacertae object, Galaxy.
Active galactic nucleus
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much higher than normal luminosity over at least some portion—and possibly all—of the electromagnetic spectrum, with characteristics indicating that the excess luminosity is not produced by stars.
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BL Lacertae
BL Lacertae or BL Lac is a highly variable, extragalactic AGN (active galactic nucleus or active galaxy).
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BL Lacertae object
A BL Lacertae object or BL Lac object is a type of galaxy with an active galactic nucleus (AGN), named after its prototype, BL Lacertae.
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Galaxy
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
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