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A Constellation is…
is…
… a region of the
sky, within official
borders set in 1928
by the IAU.
• Often recognizable
by a pattern or
grouping of stars.
• Some patterns, like
the Winter Triangle,
span several
constellations.
These are familiar
shapes but not official
constellations
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
More asterisms
Cygnus
“a real constellation”
constellation”
The big dipper
z
Actually part of Ursa
Major
Image from:
The Big Bear
http://www.physics.csbsju.edu/astro/constellations/ursa_major_l.html
Or Big Raccoon?
z
z
The summer triangle
z
z
Asterisms
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
Lyra—another real constellation
Prominent Constellations
-Sagittarius.
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
1
Scorpius
Orion
z
Betelguese
z
z
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
Not what it appears!
Orion Nebula
Orion Nebula
Betelguese
Radius of
Earths
orbit
about sun!
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
The view from here:
Celestial Astrononomy
Even though we know the Earth goes
around the sun and not vice versa..
z Don’
Don’t we?
z 1/5 adults in USA don’
don’t!
z Its useful to think about a sphere of
celestial objects surrounding the Earth
z The signs of the zodiac are the
constelltions that are along the sun’
sun’s
path—
path—the ecliptic!
z
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
Planetary
systems
forming
within!
The Celestial Sphere
The sky above looks like
a dome…
dome…a hemisphere..
z If we imagine the sky
around the entire Earth,
we have the celestial
sphere.
sphere.
z This a 22-dimensional
representation of the sky
‡ Because it represents
our view from Earth, we
place the Earth in the
center of this sphere.
z
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
2
The Celestial Sphere
Finding the North Celestial Pole
North & South celestial poles
z
the points in the sky directly above the Earth’s
North and South poles
Image
from
younge
Observer
s
Merak
celestial equator
Dubhe
the extension of the Earth’s equator onto the
celestial sphere
ecliptic
the annual path of the Sun through the celestial sphere,
which is a projection of ecliptic plane
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
The Daily Motion
daily circles --- CCW looking north, CW looking south
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Polaris
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Star Trails in two hemispheres
Southen Hemisphere
Northen Hemisphere
Which direction
How long was the shutter open?
© 2004 Pearson Education Inc., publishing as
AddisonAddison-Wesley
do the stars move?
Images from NASA/APOD
3
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