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A group of growing
stars in a cluster.Life and death of a star
throughout the universe, new stars form
and old stars die. the birthplaces of stars
are clouds of gas and dust scattered through
space. stars the size of the sun shine for
about 10 billion years. the most massive stars
(which contain 100 times as much matter as
the sun) shine very brightly, but live for a
shorter time—only about 10 million years.if you Look at the sky on a clear dark
night, it is possible to see up to about 3,000 of
the billions of stars in our galaxy. although they
appear as tiny dots, they are, like our closest star
the sun, huge, hot balls of gas, deep in space.
some stars are gigantic—if placed in the center
of our solar system, they would stretch beyond
earth’s orbit. others are far smaller, about the
size of our planet, and give off only faint light.
stars are unimaginably distant. Light from even
our nearest star (apart from the sun) takes more
than four years to reach us.
ancient skywatchers noticed that stars seem to
form patterns in the sky. they imagined that the
shapes represented pictures called constellations.
these constellations, such as the Great Bear, are
still useful for learning the positions of the stars.
astronomers identify the brightest stars with
individual names, or by their constellation
combined with a Greek letter, such as alpha, beta,
or gamma. for instance, the second brightest star
in the constellation of Cygnus (the swan) is Beta
Cygni, or albireo.red Giant
as a sunlike star runs low in
hydrogen, it swells into a cooler,
larger star called a red giant. this
will happen to our own sun in
about 5,000 million years.Birth of a star
Gravity pulls parts of a nebula
into blobs called globules. these
get smaller and spin faster, finally
breaking up into a few hundred
“mini globules.” each of these
will eventually become a star.star starts to shine
When the center of the protostar reaches about
18 million°f (10 million°C), nuclear reactions
begin, which slowly change hydrogen into helium.
the protostar begins to shine, and has become a true star.supernova
When a massive star dies, it
collapses in less than one second.
this is followed by a colossal
explosion called a supernova. the
explosion produces other substances
which scatter through space in an
expanding gas cloud.red superGiant
some dying stars grow into huge,
cool stars called red supergiants,
which can be up to 1,000 times
the diameter of the sun. a red
supergiant contains many substances
formed by nuclear reactions.pLanetary neBuLa
at the end of its life, a red giant blows off its
outer layers of gas. these make a glowing shell
called a planetary nebula, which eventually
disperses. at the center is a white dwarf, a tiny
hot star that is the burned out core of the red giant.
it will outlast the nebula by billions of years.Death of a star about
the size of the sunneBuLa
stars are born from great clouds
of dust particles and hydrogen
gas, called nebulae. the word
nebula (plural nebulae) comes
from the Latin for “mist.”Temperature at center of
red supergiant is about
18 billion°F (10 billion°C).The planetary nebula
survives only for a few
thousand years.White dwarfThe gas and dust in a
miniglobule pack closer
together, and it spins
faster and gets hotter. The
mini globule has become
a protostar (a young star).neutron star
a supernova may leave a neutron
star—a spinning ball with a mass
greater than the sun’s, yet only about
10 miles (16 km) across. as a
neutron star spins, it sends out
powerful beams of radiation.BLaCk hoLe
the remains of a very massive star may collapse
into a tiny volume, forming a black hole. the
gravitational pull of a black hole is so strong
that matter and
radiation, such as
light, cannot
escape from it.Stars 503-
Death of a
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