Astrognome 100 Great Stars Introduction
Following on from the Astrognome A-Z of constellations I intend to
present the Astrognome 100 Great Stars. Many people I am sure could
suggest an alternative 100 stars but hey this is my selection. I have
tried to stick with the brighter and better known stars.
thought it would be useful to present a very short introduction to
into the night sky there appear to be millions of stars, however on
any clear night from anywhere really dark site away from city lights
it is possible to see around 3,000 stars without a pair of binoculars
or telescopes. The stars appear to be randomly spread across the sky.
stars are actually grouped into patterns or constellations these tell
stories from ancient Greece. However
although the star stories are Greek most of the star names we use
today are Arabic.
are 88 constellations in the sky, 48 date back to the times of
ancient Greece while the other 40 constellations were added in more
modern times, by modern I mean the 15th
centuries. Most of the modern ones are
in the southern hemisphere and were added when European explorers
went there, while some were added in the northern hemisphere to fill
gaps between the classical constellations.
you look at a star map or an app on your phone or use a tablet you
will see the stars have strange looking symbols besides them. These
are letters from the Greek alphabet. In 1603 Johann Bayer allocated
the 24 brightest stars of each constellation a Greek letter. In
theory the brightest star is alpha followed by beta, gamma etc until
omega. However we will discover that this system does not always
brightness of a star is measure by its magnitude with the brightest
stars having minus numbers and the larger the magnitude number the
fainter the stars. Assuming you are in a very dark site and have good
eyesight we can see stars to magnitude 6 with our eyes without using
binoculars and telescopes. You will notice that some stars are much
brighter than others this can be because they are fairly close to us,
or because they are genuinely very bright stars. However appearances
can be deceptive because some stars only appear faint because they
are a very long way away.
use the speed of light to measure the distance to the stars, although
we use the mile to measure distances on Earth it is too small a unit
in space. Astronomers use the speed of light to measure the distances
to the stars. Light travels at a speed of 186,000 miles per second or
300,000 km per second. In one year a particle of light will travel
around 6 million million miles that is a 6 followed by 12 zeroes.
Stars can be 10s, 100s 1,000s or even millions of light years away!
you look at the stars it is possible to see that they are different
colours and rather surprisingly blue stars are hotter than red stars.
I know we say that things are red hot, meaning that's very hot, but
if you look at a flame around the edge it will appear reddish while
in the middle it is blue. This is the hottest part of the flame. And
although stars don’t burn like fire they produce their energy
through atomic reactions the colour principle is the same. Therefore
when you look at a blue star it is much hotter than a red star.
Astronomers divide the stars into different classes by using a series
of letters with O class stars the hottest and M class stars the
do come in different sizes giants and dwarfs and although our the Sun
is very big by our standards, it is about 900,000 miles across some
stars are much bigger.
it for this very brief introduction to the stars, I hope you found
this short section helpful.