Download Sky Motions - Grosse Pointe Public Schools

Sky Motions
 Diurnal Motion
 Annual Motion
DIURNAL 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
Circumpolar
Stars
Equatorial
Stars
View from the North Pole
View from the Equator
Coordinate System
Celestial Meridian

Circle going through north and south
points on the horizon and the zenith
Z
Celestial 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.
Zenith
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 0o while a star directly
overhead (this point is called the z
 http://astro.unl.edu/naap/motion2/s
tarpaths.html enith) has an altitude
of 90 o.

What is the altitude of a star
that is exactly halfway
between the horizon and the
zenith?
Polaris and Altitude

Polaris “north star”
1 degee from NCP

Altitude of polaris is always equal to
the latitude of the observer.
Equator 0º altitude = 0º
North pole 90º altitude= 90º aka
Grosse pointe 42º altitude = 42º
Zenith
South pole

Can you see polaris?
Nope!
Annual Motion
ANNUAL MOTIONEarth’s revolution
 Constellations
the year.
move westward during
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
Horizon Calendar
Sunrises
The Sky
andDome
Sunsets
Polaris
On the day of an
summer
solstice…
W
On the day of an
winter solstice…
S
On the day of an
equinox…
E
N
Polaris
W
S
Winter
Solstice
Vernal or
Autumnal
Equinox
Summer
Solstice
N
E
Starting Points for the Sun
Sunrise in Athens
Stonehenge
Earth’s Annual Motion
Leo
NCP
Celestial
Sphere
Autumnal
Equinox
23.5°
Ecliptic
Vernal
Equinox
SCP
Celestial
Equator
Sun’s Motion Tool
Inclined Pole causes Seasons
Northern
Hemisphere
Summer
N
S
Northern
Hemisphere
Winter
23.5°
Sun’s motion along the Ecliptic
Sun’s Motion
“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”