Constellations
Constellations are visible groups of stars that appear as patterns
in the sky. The Southern Cross and Orion are constellations. Different
cultures have different names and see different patterns in the same
sets of stars. For example, Orion "The Hunter" is also known
as "The Turtle" to the Thai people.
Astronomically, constellations are not real groups of stars like
galaxies. Constellations do have an important role to play as guides
or references in the night sky. The stars in the Southern Cross and
pointers display this well; they are important as direction finders
in the Southern Hemisphere. The stars themselves range in distance from
Earth to Alpha Centauri at 4.3 light years to Delta Crucis at 590 light
years.
The history of constellations
From the earliest times, constellations, parts of
constellations (known as asterisms), and individual stars have received
names depicting meteorological phenomena or religious and mythological
beliefs. Constellation names are steeped in history, with many coming
from the ancient Greeks. Forty eight constellations were named in ancient
times, with another 40 constellations added by European astronomers
in the 17th and 18th centuries.
In the 20th century, the sky or celestial globe was divided up
into 88 constellations with precise boundaries by the International
Astronomical Union. By 1930, all stars had been assigned to a constellation.
This aided in easier identification and positioning of stars in the
sky, but says nothing about their nature or true place in space, only
their direction from Earth.
Viewing southern constellations
On a clear, dark night, the southern night sky is spectacular - especially
in winter, when we have the best possible view of the Milky Way.
The most well known of the Southern Hemisphere constellations is
Crux Australis, better known as the Southern Cross. Its long axis is,
by chance, directed to the point in the sky called the South Celestial
Pole, which is exactly above the southern horizon. It is so far south
that its stars were not well known by ancient Northern Hemisphere astronomers.
The first references to it as having the shape of a Cross seem to come
from Andrea Corsali, the Italian explorer, in 1517.
The next most well known is probably Orion, a giant hunter from
Greek Mythology. The stars do indeed appear to have the shape of a man
wielding a club and having a sword attached to his belt. It is the stars
of the belt that make Orion easy to spot - the belt is formed by three
bright stars in a nearly straight line.
The Southern Cross, Orion, and other southern constellations are shown
on the star map.
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