12
Balls of gas
A star is a huge, glowing ball of hydrogen gas
that shines because of nuclear reactions in its
core. The hottest stars die within a few million
years. Red dwarf stars are the coolest and live
the longest.
There are four
young, massive
stars at the
center of the
Orion Nebula.
Orion Nebula
This galaxy is 15,000 light-
years away from Earth.
The clouds are
many different
colors because
they are made up
of different gases
and dust particles.
The small orange dots
are stars that are still
forming.
SPACE
O Constellations Only a few thousand stars
can be seen without a telescope. All of these
are in our own galaxy. Ancient people saw
patterns and shapes (constellations) in them
and named them
after mythological
creatures or
people. The most
famous are the
12 zodiac
constellations.
They form a belt
across the sky.
URSA MAJOR The
seven brightest stars,
located in the Bear’s
hindquarters
and tail, form
the well-known
Big Dipper.
TAKE A LOOK
O Most stars are born inside
giant dust clouds called
nebulas. Parts of these clouds
collapse and as they shrink,
the gas and dust get hotter and
forms a star. When nuclear
reactions begin in its core,
radiation makes the surrounding
material glow. Eventually, this is blown
away and the star appears.