A blazar is a type of galaxy, related to
quasars and BL Lacertae objects, which displays
extremely intense, broad and rapidly varying
electromagnetic radiation. This emission is thought
to originate from a plasma jet pointing in our
direction, and is believed to be powered and
accelerated by a super-massive black hole, perhaps
as much as a billion time more massive than our Sun.
Blazars have the following characteristics:
- It appears point-like on the sky.
(Some have fuzzy nebulae around them,
but most of the radiation comes from
a point source.)
- They have a "smooth" spectrum,
i.e. flatter, and no strong absorption lines,
as stars have.
- The visible light they emit is often
polarized.
- The radiation in all frequencies
varies more rapidly, and with greater
intensity than that of a quasar.