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THE
DIFFERENT TYPES OF STARS
The Sun is an average sized yellow star. It
is about 1 million kilometres wide and is about 4.5 billion years
old. However, when the Sun gets older (in about 5 billion years), it will no
longer be an average-sized yellow star. Instead, it will increase
in size and become a Giant star, before using up almost all its
energy and collapsing into a Dwarf Star. Below is a list of the
different types of stars:
DWARF STARS
The nearest star to the Sun, Proxima Centauri, is a Red Dwarf star. It is a
star with a diameter (width) less than half the diameter of the
Sun, a surface temperature about 2000°c to 3000°c cooler. The Sun is also about 10,000 times brighter
than Proxima Centauri. White Dwarfs are similar to Red Dwarfs,
except that their surface temperatures are much higher, and shine
white instead of red. When the Sun comes to the end of its life, it will become a
White Dwarf. It will be much smaller than it is now, not quite as
bright but twice as hot. Its matter (particles) will be more
densely-packed together. There are also Black Dwarfs. These are
stars that we cannot see, which have used up their energy for
producing light, but are still closely-packed but still have a
strong gravitational pull.
NEUTRON
STARS (PULSARS) AND BLACK HOLES
A neutron star is a very small star, perhaps only 20 kilometres
across, which is just as heavy as the Sun is now. Its matter is extremely densely-packed
together. When a Giant star collapses as it dies, it causes a
huge explosion called a Supernova. This explosion, producing vast
amounts of cosmic dust and appearing like another nebula in
space, ends with the star shrinking or totally disappearing. A
neutron star, which spins very fast, gives out huge pulses of
radiation. This is why it is known as a Pulsar. If it does
completely disappear it becomes a Black Holes, appearing to suck
in objects orbiting or approaching close to it.
AVERAGE-SIZED
STARS
Most average-sized stars, like the Sun, are about half-way through their life. They have
surface temperatures about 6000°c and glow are bright yellow,
almost white, colour. They will swell up to become a Giant stars,
and then shrink to become White Dwarfs.
BLUE-WHITE
STARS
Some stars use up their hydrogen quicker than other stars. The
Sun uses up its hydrogen steadily, and will have a life of about
10 billion years. Stars which burn up their hydrogen supplies
quickly are much hotter than Sun-like stars. This heat causes them to glow bright
blue, or blue-white. Sirius is the brightest star in the sky
after the Sun,
and has a surface temperature of about 10,000°c and is two and a
half times bigger than the Sun. These hot stars are not necessarily always bigger
than the Sun.
They are just hotter and shine brighter.
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SUPERGIANTS
An old Blue-white star becomes a Supergiant. They expand, just
like average-sized stars expand to become Giant stars. Because
they are beginning to run out of hydrogen, they cool down and
glow a more orangey colour. A star called Betelguese is extremely
old, but also extremely big. In fact, it is 500 times wider than
the Sun and would, if it was at the centre
of the Sun's Solar System, be big enough to stretch nearly to
Jupiter. This giant star will one day
collapse in a huge explosion called a supernova and will become a
neutron star or maybe even a Black Hole.
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