constellation wars

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Transcript constellation wars

Good night: see about 3000 points of light (unless you live here in WA)
Different cultures have all looked for patterns in the stars
The brightest stars visible were fit into patterns called constellations
Constellation: the pattern of stars seen
in the sky, and refer to a specific region
in the sky
Ancient Astronomers named
• Mythological beings
• Heroes (Orion)
• Animals (Leo, Scorpio, etc.)
Different cultures grouped some of the same basic stars.
Often varying interpretations
• Example: “The Big Dipper (North America)
• “The Wagon” or “The Plough” (Western Europe)
• Tail of the “The Great Bear” (Ancient Greeks)
• Leg of an Ox (Egyptians)
• “Stag” (Siberians)
Many began to believe that the relative
position of the stars and planets at a
person's birth could determine that
person’s destiny
Helping them to “see” into the future
Polaris (Located in Little Dipper):
• Help indicate the direction of north
• Near constant location in the sky helped travelers for centuries
• Location is nearly at the northern horizon year-round while other
stars circle around it.
• Polaris does not rise or set
Why is its locating consistent?
• The axis of the Earth is pointed
almost directly at it
• Help astronomers to specify large areas of the sky (geologists and
• Primitive calendars predicting/planning harvest and planting seasons.
Ancient cultures knew when certain stars appeared on the horizon before
daybreak, it would be the beginning of spring
Example of a spring
star chart for the
Northern Hemisphere
The stars that make up any constellation are not actually close together in
• They are bright enough to be observed with the naked eye
• They happen to lie in the same direction in the sky as seen from Earth
Roughly 88 constellations in all
• Most are visible from North America at some time during the year
Humans lack depth perception we look into space:
• Our perspective is that all the stars lie same
The ancient Greeks mistook this illusion for reality
• Believed Earth to be surrounded by a great
Celestial Sphere
Constellations seem to move across the sky from East to West
• Ancient astronomers understood that the relative locations of stars
remained unchanged
• Conclusion: the stars were firmly attached to a Celestial Sphere that
surrounded the Earth.
Celestial Sphere: surrounds the Earth, is a canopy of stars resembling an
astronomical painting on a heavenly ceiling
Star Trails: show how all stars appear to move in circles around a point very
close to the star Polaris
Today we understand:
• Earth does not lie in a the
center of a great ball
• Apparent motion of the stars
is the result the Earth’s
rotation, not the sphere’s
Celestial Poles: The points where
Earth’s axis intersects the celestial
Celestial Equator: Midway
between the north and south
celestial poles
• that the Earth does not really lie in the center of a
giant ball
Names given to certain locations:
• North Celestial Pole (NCP): The point directly
above the Earth’s North Pole
• South Celestial Pole (SCP): The point directly
above the Earth’s South Pole
• Celestial Equator: represents the Earth’s equator
into space
• Ecliptic
Ecliptic: the ecliptic is the plane of Earth's orbit around the Sun
• The apparent path of the Sun on the celestial sphere
• as seen from the Earth's center
• Sun’s path is not normally noticeable from the Earth's surface
• Earth rotates
• Carrying the observer through the cycle of sunrise and
sunset, concealing the apparent position of the Sun
against the background stars.