Whole Earth Blazar Telescope

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

The Whole Earth Blazar Telescope (WEBT) is an international group of astronomers founded in 1997 to study blazars, a type of active galactic nucleus that can vary in brightness very quickly, sometimes in hours or less. The collaboration brings together many telescopes that observe in optical, near-infrared, and radio wavelengths. Because the observatories are spread around the world, they can monitor a target almost continuously as the Earth turns, with coverage moving from east to west. WEBT observations are often combined with higher-frequency observations—from ultraviolet to gamma rays—made by space and ground-based facilities, giving a view of blazar emission across nearly the entire electromagnetic spectrum. The goal is to understand the physical processes behind the variable emission, which comes from a jet of plasma pointing close to our line of sight, powered by a supermassive black hole at the galaxy’s center.

WEBT began in autumn 1997, founded by John Mattox of Boston University as a collaboration among optical observers. In 2000, Massimo Villata of the Turin Observatory became the leader. A formal charter outlined aims and management, and soon radio and near-infrared observers joined. By February 2009, WEBT had organized 24 observing campaigns with more than 100 telescopes. Each campaign targets a specific blazar and is led by a Campaign Manager responsible for planning the observations, collecting and analyzing data, and helping publish the results.

Over the years, WEBT campaigns have covered many well-known blazars. In 2007, the project launched the GLAST-AGILE Support Program (GASP) to provide long-term, multi-wavelength monitoring that complements gamma-ray satellites. GASP monitors 28 bright blazars with periodic data collection and analysis. Examples include 3C 273, 3C 279, BL Lacertae, Markarian 421, OJ 287, PKS 2155-304, and 1ES 2344+514, among others.

Since its start, WEBT has contributed to more than 160 scientific publications, helping scientists better understand how blazars emit and vary over time.