Life of a Star (Basics) (The Life of a Star (Birth of a Star:
Life of a Star (Basics)
Birth of a Star:
1. Stars are born in a region of high
density Nebula, and condenses
into a huge globule of gas and
dust and contracts under its own
A region of condensing matter will
begin to heat up and start to
glow forming Protostars. If a
protostar contains enough matter
the central temperature reaches
15 million degrees centigrade.
At this temperature, nuclear
reactions in which hydrogen
fuses to form helium can start.
The star begins to release energy,
stopping it from contracting even
more and causes it to shine. It is
now a Main Sequence Star.
Small Star and Main Sequence:
5. A star of one solar mass remains in
main sequence for about 10 billion
years, until all of the hydrogen has
fused to form helium.
Death of Star
6. The helium core now starts
to contract further and reactions
begin to occur in a shell around the core.
The core is hot enough for the
helium to fuse to form carbon.
The outer layers begin to expand,
cool and shine less brightly. The
expanding star is now called a Red Giant.
The helium core runs out, and
the outer layers drift of away
from the core as a gaseous shell,
this gas that surrounds the core is
called a Planetary Nebula.
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Massive Star and Main Sequence:
5. A star of 10 solar masses shines
steadily until the hydrogen has fused
to form helium ( it takes billions of
years in a small star, but only
millions in a massive star).
The massive star then becomes
a Red Supergiant and starts of
with a helium core surrounded
by a shell of cooling, expanding gas.
In the next million years
a series of nuclear reactions
occur forming different elements
in shells around the iron core.
The core collapses in less than a
second, causing an explosion called
a Supernova, in which a shock wave
blows of the outer layers of the star.
(The actual supernova shines brighter
than the entire galaxy for a short time).
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Massive stars have a mass 3x times that of the Sun. Some are 50x that of the Sun about 10 solar masses