Active Galactic Nuclei
The largest identified class of high-energy gamma-ray
sources is a type of Active Galactic Nuclei (AGN) called blazars.
The Energetic Gamma Ray Experiment Telescope (EGRET)
on board the Compton Gamma Ray Observatory detected more 
than
50 blazars: GLAST will see thousands. These large redshift
extragalactic objects are incredibly powerful sources, each believed to contain
a central rotating supermassive black
hole with jets of 
relativistic
particles emanating from near its poles. AGN are generally only detected as
high-energy gamma-ray sources when one of the jets is directed towards the observer,
a geometry for which the accretion
torus surrounding the black hole does not obscure us from the black hole or
the inner part of the jet. Even for this geometry, however, gamma rays are the
only kind of electromagnetic radiation that can directly escape from the central
region. Thus, GLAST observations of blazars will provide us with a unique opportunity
to study what is happening on the doorsteps of billion-solar-mass black holes.
GLAST studies of high-energy gamma-ray emission from blazars will help
answer some of the most important questions we have regarding AGN:
- What types of particles are being emitted into the jets?
- How does a black hole create jets?
- What are the properties of the black hole?
than
50 blazars: GLAST will see thousands. These large redshift
extragalactic objects are incredibly powerful sources, each believed to contain
a central rotating supermassive black
hole with jets of