Essay, Research Paper: Constellations

CONSTELLATIONS

For untold thousands of years men have traced the outlines
of familiar things among the stars. These patterns in the night
sky are called constellations, from Latin words meaning together
and stars.


Many of the constellations have names that are very old. The
Sumerian shepherds and farmers of Mesopotamia 7,000 years ago may
have called the Bull, the Ram, the Lion, and many other
constellations by the same names we use. Students of history are
sure these names started in Mesopotamia because the choice of
animals suggests this. If the names had first been used in Egypt,
there should be a hippopotamus or elephant among the stars. If
they had started in ancient India, there should be a tiger or
crocodile. (See also Astronomy.)


The later people of Mesopotamia took over the old Sumerian
names for the constellations and still later the Greeks adopted
them. The Greeks added many names of heroes and demigods to the
list of constellations. The Romans used the Greek list but
translated the names into Latin.


About AD 150 the Egyptian astronomer Ptolemy listed the 48
constellations known to him in his book the 'Almagest'. His list
did not cover the entire sky. There were blank spaces between
constellations; and there were no constellations at all for the
southernmost stars because these could not be seen from the
Mediterranean region. In later centuries astronomers added
constellations to Ptolemy's list. Some of these later
constellations are named for scientific instruments, such as the
Sextant, the Compasses, and the Microscope. Others bear the names
of birds and beasts in tropical regions (the Giraffe, the
Chameleon, the Toucan). Today 88 constellations are recognized by
astronomers.


To most people a constellation is a group of bright stars,
but to an astronomer it is a definite area in the sky. Thus every
star, no matter how dim, lies in one constellation or another,
just as any point in the world is in one country. Although all
the stars in the same constellation look close together in the
sky, they are not necessarily close in space because some may be
much farther out in space than others. The boundaries of the
constellations used to be very irregular and had many curved
lines. In 1928 astronomers straightened them out so that the
outline of any constellation includes only straight lines running
north and south or east and west. Astronomers use the
constellation names to identify most bright stars and all
variable stars, so it was important to make the boundaries clear
and precise (see Star).


The constellations are useful to astronomers today not for
their connections with ancient myths, but for telling where in
the sky different stars can be found. Many of the brightest stars
have individual names that come from Greek, Latin, or Arabic, and
the navigators of ships and aircraft call them by these names.
Astronomers, however, find it more convenient to name them by
their constellations, with a Greek letter to distinguish the
different stars in each constellation. For example, Polaris, the
Pole Star, in the Northern Hemisphere, is the brightest star in
the constellation Ursa Minor, the Little Bear, and the
astronomers' name for it is alpha Ursae Minoris, or a UMi for
short.


The path of the sun among the stars is called the ecliptic.
The twelve constellations that lie along the ecliptic form the
Zodiac, or birth-sign constellations. The other constellations
are divided into those north of the Zodiac and those south of it.


From one place on the Earth different constellations are
seen at different times of the year. This happens because, as
well as turning on its axis, the Earth is always moving around
the sun, making one orbit each year. A star that is visible at
night during one part of the year may appear close to the sun six
months later; it would not then be seen at night.


Some constellations can be seen only from the Northern
Hemisphere and some only from the Southern Hemisphere. The
constellations of the Zodiac can be seen from both hemispheres.
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constellations are actually a pattern of stars formed by ancient greeks that were amazed to see that stars were in patterns and then they thought that the so called patterns were actually figures of people who were to be famous