Download Canis Major

Constellations
• Astronomy: A pattern of stars
– 6000 visible stars
– No physical proximity
– The sky appears as 2-dimensional
• Astrology
– Origins of many cultures
– Storytelling / folklore
– Seasonal Events: planting, harvest, floods, drought,
religious/cultural events
– Pre-dates calendars
• 88 Constellations – North & South Hemispheres
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Orion in 3-D
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Orion: The Hunter
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Orion: The Hunter
Due South @ 9 pm tonight
Betelgeuse, Rigel, The Orion
Nubula (Orion’s Sword)
Orion stands by the river Eridanus
accompanied by his faithful dogs, Canis
Major and Canis Minor, hunting various
celestial animals, including Lepus, the
hare, and Taurus, the bull. Orion was in
love with Merope, one of the Seven Sisters
who form the Pleiades, but Merope would
have nothing to do with him. Orion's
tragic life ended when he stepped on
Scorpius, the scorpion. The gods felt sorry
for him, so they put him and his dogs in
the sky as constellations and all of the
animals he hunted up there near him.
Scorpius, however, was placed on the
opposite side of the sky so Orion would
never be hurt by it again.
Celestial Coordinates: Extension of the Earth’s Coordinates
• FIXED positions
-North celestial pole
(known as “Polaris”)
-South celestial pole
-Celestial equator
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Right Ascension & Declination
Analogous to Longitude and Latitude
Right Ascension (RA)
measured Eastward in
hours and minutes from
the position of the sun at
vernal the equinox
(Spring).
360o / 24hr = 15o / hr
Declination (dec)
measured in degrees north
or south above the celestial
equator.
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Horizon System: Sky Coordinates
Zenith: point directly overhead at any time
Horizon: the lowest point you can see (the ground)
Meridian: N / S line dividing the sky into E - W
Altitude: angular distance above horizon
Azimuth: compass direction
North = 0o
East = 90o
South = 180o
West = 270o
Nadir: directly
downward
Altitude = 60o
Azimuth = 135o
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Daily or diurnal motion
- Apparent westward motion of sun, moon, planets, stars in the sky
Earth rotates on its own axis
every 24 hours in an
EASTWARD direction
(from above counter clockwise)
To us, it appears as if
objects in the sky are
moving WESTWARD—
Sun rises in the E
Sun sets in W
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Check your knowledge-The position of Polaris, the “North Star”,
in the night sky in the United States:
(a) is always directly overhead
(b) is always near the horizon
(c) is at 23.5 degrees from the horizon
(d) depends on your location
ANSWER: (d)
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o
The background stars move 1 westward per day
resulting in the same star rising 4 minutes earlier each
day.
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As Earth orbits our Sun,
different constellations
are visible at different
times of the year.
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Position of sunrise and sunset changes due to
the orientation of the Earth with the Sun
•Sun rises North of East in Summer
Sun sets North of West in Summer
•Sun sets South of East in Winter
Sun sets South of West in Winter
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Using the Planisphere
Location of stars and constellations in the sky
Constellations in the zodiac
The ecliptic (path of the sun) and celestial equator
Position (azimuth) and time of sunrise and sunset
Location & visibility of planets
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