Transcript Constellations

Constellations
A natural human tendency is to see patterns and relationships
between objects even when no true connection exists.
Long ago, people connected the brightest stars into
configurations called constellations, which ancient
astronomers named after mythological beings, heroes, and
animals—whatever was important to them.
Does that cloud look like a “bunny” to you.
OR
What do you see in that ink blot?
Orion
• Some locations are better
• Stars are widely
varied in color
Orion
Ursa Major
Ursa Major
Ursa Minor
Ursa Minor
Scorpius
Scorpius
Cygnus
Cygnus
Sagittarius
Sagittarius
Cross Cultures
Astronomers of ancient China saw mythical figures different
from those seen by the ancient Greeks, the Babylonians, and
the people of other cultures, even though they were all
looking at the same stars in the night sky.
Interestingly, though, different cultures often made the same
basic groupings of stars, despite widely varying
interpretations of what they saw.
For example, the group of seven stars usually known in North
America as "the Dipper" is known as "the Wagon" or "the
Plough" in Western Europe. The ancient Greeks regarded
these same stars as the haunches and tail of "the Great
Bear," while the Egyptians saw them as the leg of an ox.
Navigation
Reasons to Group stars and create constellations:
• Entertainment
• Honor
– Hero Hall of Fame
– gods or leaders
• Keep track of where things are and the time
– Calendars, Events
• Navigation
Patterns are Deceiving
Constellations are NOT
physically associated
with each other, they just happen
to be along your line of sight.
Our Moving Observatory
Star trails
Looking SouthEast
Looking North
What’s Your Sign
The Sun’s Position Determines your sign.
The Zodiac
Summer Constellations
Looking South
Lyra and Cygnus
Directly
Overhead
After Sunset
in the summer
and early
fall.
Winter Constellations
Looking South
Star Atlas Artistry
Can You Find:
Orion
Taurus
Canis Major
Cancer
Gemini
Hipparchus
Most atlases of today have their origins with those
that were derived from Hipparchus and used his
“magnitude” system.
1st Rank Stars (The brightest stars in the sky)
6th Rank Stars (Barely visible with the unaided eye)
Later, the magnitudes were rigorously defined so
that a 5 magnitude difference = 100 x the intensity.
Magnitudes
Magnitudes
are more
precise
and changes
in intensity
are matched
with apparent
magnitudes.
Vega = 0.0
Magnitude Scale
Note:
DM = 5 - 0 = 5
DI = 100 1 = 100
or
DM = 8 - 3 = 5
DI = 1600  160 = 100
Brightness Scale
I = intensity
I1/I2 = 2.512(m2-m1)
mv = apparent magnitude
Altitude - Azimuth
• Horizon based coordinate system
– Horizon dependent (different for each observer)
E
N
S
W
Altitude - Azimuth
• Horizon based coordinate system
– Horizon dependent (different for each observer)
N
• Azimuth Angle (degrees)
– measured CW from N to E
0
90 E
– N = 0o, E = 90o, S = 180o, W = 270o W 270
180
S
E
N
S
W
Altitude - Azimuth
• Horizon based coordinate system
– Horizon dependent (different for each observer)
N
• Azimuth Angle (degrees)
– measured CW from N to E
0
90 E
– N = 0o, E = 90o, S = 180o, W = 270o W 270
• Altitude Angle(degrees)
– horizon to star
– Horizon = 0o
– Zenith = 90o N
180
S
E
S
W
“Bowl” Diagram
Orienting yourself to a local horizon.
Zenith
NCP
Celestial Equator
N
S
W
Celestial Orientation
Right Ascension - Declination
• Geocentric Coordinates
– Observer Independent
North Celestial
Pole (NCP)
Celestial Equator
(Earth’s Equator)
Toward
the Vernal
Equinoxe (Position of the Sun on March 21-22
Right Ascension - Declination
• Right Ascension (hours)
– Measured from the Vernal Equinoxe along the C.E.
– Vernal Eq. = 0 hours
Celestial Equator
(Earth’s Equator)
RA
Toward
the Vernal
Equinoxe = 0 hours
Right Ascension - Declination
• Declination (degrees)
– Measured from the Celestial Equator to the Pole
NCP
– CE = 0o
– NCP = 90o
DEC
Toward
the Vernal
Equinoxe = 0 hours
Celestial Equator
(Earth’s Equator)
Sky Atlas
Right Ascension
Magnitude
Sky Atlas
Constellation
Lyra,
Bright Star
Vega