A black hole is an object whose gravitational pull
is so intense that
nothing, not even light, can escape it once inside
a certain region
called the event horizon. As gas and dust (or even
entire stars) are
sucked in, the material is accelerated and heated
to very high
temperatures. This in turn results in the emission
of X-ray light. Black
holes containing lots of nearby gas and dust such
as this Perseus
cluster galaxy produce tremendous amounts of X-ray
|Artist's concept of a black hole.
Still more X-ray light is generated when some of the
into the black hole doesn't fall in but rather is
spit out at incredibly
fast speeds (close to the speed of light). To understand
material is spit out, think of the analogy of someone
trying to eat too
much food at once. Such a messy eater will have food
fall from their mouth.
Black holes are like such messy eaters. Some material
won't reach the
event horizon but instead is caught up in powerful
existing around the black hole. These "jets"
not only shoot some
material away. They also emit prolific amounts of
energy from radio
waves to visible light to X-ray light.
The jets of material shooting out from the central
black hole of the
Perseus cluster have blown out large holes (cavities)
in the nearby
gaseous medium and -- like waves propagating on a
pond surface -- have
set up ripples throughout the entire cluster medium.
These ripples are
the sound waves.