Page 28 - Ultimate Visual Dictionary (DK)

THE UNIVERSE

Massive stars SUPERNOVA

MASSIVE STARS HAVE A MASS AT LEAST THREE TIMES that of the Sun, and some
stars are as massive as about 50 Suns. A massive star evolves in a similar way to a
small star until it reaches the main sequence stage (see pp. 24-25). During its life
as a main sequence star, it shines steadily until the hydrogen in its core has fused
to form helium. This process takes billions of years in a small star, but only millions
of years in a massive star. A massive star then becomes a red supergiant, which
initially consists of a helium core surrounded by outer layers of cooling, expanding TARANTULA NEBULA BEFORE
gas. Over the next few million years, a series of nuclear reactions form different SUPERNOVA
elements in shells around an iron core. The core eventually collapses in less than
a second, causing a massive explosion called a STRUCTURE
supernova, in which a shock wave blows OF A RED SUPERGIANT
away the outer layers of the star.
Outer envelope consisting
Supernovae shine brighter than an mainly of hydrogen
entire galaxy for a short time. Layer consisting
Sometimes, the core survives mainly of helium
the supernova explosion. If
Layer consisting
the surviving core is mainly of carbon
between about one and a
Layer consisting
half and three solar
mainly of oxygen
masses, it contracts to
become a tiny, dense Layer consisting
mainly of silicon
neutron star. If the
core is greater than
three solar masses, Shell of hydrogen
it contracts to fusing to form
helium
become a black hole
(see pp. 28-29).
Shell of helium
fusing to form
carbon
Shell of carbon
Surface temperature fusing to form
5,500°F (3,000°C) oxygen
Cooling, expanding Shell of oxygen fusing
outer layers glow red to form silicon

Core of mainly iron at 5.4-9
billion °F (3-5 billion °C) Shell of silicon fusing
to form iron core
LIFE OF A MASSIVE STAR OF
ABOUT 10 SOLAR MASSES Star producing
About 2 million
Glowing miles (3 million km) energy by nuclear
fusion in
ball of gas
Dense globule (mainly hydrogen) core
condensing to
form protostars
Natal cocoon (shell
of dust blown away
Cool cloud of gas by radiation from
(mainly hydrogen) protostar)
and dust
NEBULA PROTOSTAR MAIN SEQUENCE STAR
Duration: a few hundred Duration: 10 million years
thousand years
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