Page 104 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

What are active These are located

A Quasars
billions of light years
galaxies? away from Earth and
viewed from
an angle.

The powerful galaxies that swallow their surroundings

galaxy is a large system of stars, gas, dust and active galaxies and their energy emission is driven by
dark matter bound together by gravity. Most supermassive black holes at their core. Such black
n
A ormal galaxies emit light from their stars, but holes actually lie at the centre of every large galaxy,
a small number give off an enormous amount of including the Milky Way, but most are now inactive.
energy from their centre in wavelengths of light that This has led many scientists to believe that all
are invisible to the naked eye. These are known as galaxies in fact started out as active.
Formation
How a galaxy goes from being active to inactive Three types of
active galaxy
There are several types of active galaxy, including
quasars, radio galaxies and blazars. However,
most scientists believe these are actually all the
same. Their theory suggests that the each type
looks different to us because it is being viewed B Radio galaxies
from a different perspective and distance. These galaxies are viewed
from side-on so the core
cannot be seen.
Speeding swirls
The matter within the jets
spirals into outer space at
speeds approaching the
speed of light. C Blazars
These galaxies have one
jet pointing towards
Earth so that we are
looking at it head-on.

2 Even more
massive

Once the supermassive
black hole has formed, it
accumulates gas and
dust to grow in size.

Stellar black
1 Supermassive
black hole holes form when
Small, stellar black holes
form when large stars large stars
collapse, but the origin of
their supermassive cousins
is still a mystery. collapse

3 Visible halo 4 Powerful jets
A swirling cloud of matter, Just before it is pulled into the
known as an accretion disk, black hole, some of the matter
forms around the black hole, is ejected outwards in two jets
feeding it more gas and dust. that align with its poles.

104 How It Works