Annual Motion DIURNAL MOTION Daily East West motion of the sky Due to the Earths rotation 15hour 36024 hours 15hour 1 in 4 minutes Stars fall into two groups Circumpolar never rise or set ID: 760044
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Slide1
Sky Motions
Diurnal Motion
Annual Motion
Slide2DIURNAL MOTION
Daily East / West motion of the sky
Due to the Earth’s rotation (15°/hour)
[360°/24 hours = 15°/hour]
[1° in 4 minutes]
Stars fall into two groups
Circumpolar - never rise or set
Equatorial
Slide3Circumpolar Stars
Slide4Equatorial Stars
Slide5View from the North Pole
Slide6View from the Equator
Slide7Coordinate System
Slide8Celestial Meridian
Circle going through north and south points on the horizon and the zenith
Z
Slide9Celestial Meridian
Objects on the Meridian are at their highest point in the sky (transit)
Astronomical noon is when Sun is on the Meridian.
Does not mean the Sun is directly overhead.
Midnight is when the Sun is on the Meridian below the horizon.
Slide10Zenith
This
is a measure of how high above the horizon the star or planet is located. A star on the horizon has an altitude of 0
o
while a star directly overhead (this point is called the
z
http://astro.unl.edu/naap/motion2/starpaths.html enith
) has an altitude of 90
o
.
Slide11What is the altitude of a star that is exactly halfway between the horizon and the zenith?
Slide12Polaris and Altitude
Polaris “north star”1 degee from NCPAltitude of polaris is always equal to the latitude of the observer.Equator 0º altitude = 0º North pole 90º altitude= 90º akaGrosse pointe 42º altitude = 42º
Zenith
Slide13South pole
Can you see
polaris
?
Nope!
Slide14Annual Motion
Slide15ANNUAL MOTION-Earth’s revolution
Constellations move
westward
during the year.
Due to Earth’s orbital motion around the Sun
Sun appears to moves
eastward
1°/day
Path of the Sun called the ECLIPTIC
Ecliptic inclined 23.5° to Equator
Horizon calendar
Slide16Horizon Calendar
Slide17S
N
W
E
Polaris
On the day of an equinox…
On the day of an winter solstice…
On the day of an summer solstice…
The Sky Dome
Sunrises and Sunsets
Slide18S
N
W
E
Polaris
Vernal or
Autumnal
Equinox
Summer
Solstice
Winter
Solstice
Starting Points for the Sun
Slide19Sunrise in Athens
Slide20Stonehenge
Slide21Earth’s Annual Motion
Leo
Slide22Celestial Sphere
Celestial Equator
SCP
NCP
Ecliptic
Vernal Equinox
Autumnal Equinox
23.5°
Slide23Sun’s Motion Tool
Slide24Inclined Pole causes Seasons
23.5°
Northern Hemisphere Summer
Northern Hemisphere Winter
N
S
Slide25Sun’s motion along the Ecliptic
Sun’s Motion
Slide26Annual Motion Affects the Nighttime Sky
Day 1
9:00 PM
Slide27Annual Motion Affects the Nighttime Sky
Day 2
8:56 PM
Slide28Annual Motion Affects the Nighttime Sky
Day 3
8:52 PM
Slide29Annual Motion Affects the Nighttime Sky
One Year Later
9:00 PM
Slide30“Stars”
Fixed Stars
Modern concept of stars
Form the Constellations
Planets - traveling or wandering stars
Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn
Meteors - “shooting stars”
Comets - “long-haired stars”
Slide31Babylonian Astronomy
Slide32Babylonian Astronomy
Star Charts
Slide33Babylonian Astronomy
Fatalistic Pre-determinism
Everything in nature pre-determined by the gods
Doesn’t lend itself to model building
Infinite time line
Slide34End of Section