CONSTELLATIONS

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CONSTELLATIONS
    Constellations are groupings of the brighter visible stars in the night sky.
Many of these groupings are based on imaginary figures that are seen on the inner
surface of a huge sphere surrounding the earth.

    They divide the celestial sphere into 88 constellations, 47 of
which date from ancient times and were listed by the astronomer Ptolemy. The
boundaries are often complex. But all segments of the boundaries lie ease-west
and north-south on the celestial sphere.
   
    Constellations are used today to show general directions in the sky. The constellations may be
divided into three groups: (1) the equatorial constellations,
which lie on each side of the celestial equator, the projection onto the sky of the
earth's equator; (2) the north circumpolar constellations, which never set for observers
at northern mid-latitudes; and (3) the south circumpolar constellations, which never
set for observers at southern mid-latitudes. The zodiac, widely used in astrology,
consists of 12 constellations through which the orbital motion. The suns yearly
path is called the ecliptic.

    The times when given constellations rise and set depends on the time of year
and on the observers position on the earths surface. Constellations also slowly shift
on the celestial sphere's coordinates because of the precession of the equinoxes and
other movements.. The star Patterns themselves slowly change because of the relative motions of the stars,
but such changes are obse...

Submitted by: digitalessays
Date Submitted: 05-10-2002
Category: Social Issues
Words: 619
Pages: 2.48