Constellations Sections of sky with recognizable star patterns
Used by ancient people for navigation Also used to keep track of
time
Slide 4
Constellations (cont.) 88 constellations Each constellation
borders another constellation (like states in a country) Every
star/galaxy belongs in 1 of the 88 constellations
Slide 5
Constellations & Seasonal Changes Different constellations
are visible in the Northern & Southern Hemispheres Due to
Earths revolution around Sun, the locations of constellations
appear to change
Slide 6
Finding Stars in the Night Sky Relative to Observer Astrolabe
Device used for measuring height of objects Used for determining
altitude of stars Needs 3 points of reference to work Zenith
Altitude Horizon
Slide 7
Zenith Imaginary point in sky Directly above observer Altitude
is always 90 degrees
Slide 8
Horizon Line where sky & Earth appear to meet
Slide 9
Altitude Angle between the object & the horizon
Slide 10
Describing Star Position Relative to Earth Astronomers use the
celestial sphere An imaginary sphere surrounding Earth
Slide 11
Parts of Celestial Sphere Celestial equator Made by extending
the Earths equator into space
Slide 12
Parts of Celestial Sphere Declination Measures star position
north or south of celestial equator Measured in degrees
Slide 13
Parts of Celestial Sphere Right Ascension Measures star
position eastward from vernal equinox Measured in hours
Slide 14
Declination & Right Ascension
Slide 15
Path of Stars Across the Sky Planets & stars appear to rise
& set Caused by rotation of Earth on its axis
Slide 16
Circumpolar Stars
Slide 17
Always visible at a certain latitude Circumpolar stars never
set Appear to circle the celestial poles
Slide 18
Due to Earths revolution, different constellations are seen at
different times of yr. Summer Constellations in Northern Hemisphere
Winter constellations in Northern Hemisphere
Slide 19
The Size & Scale of the Universe Stars are much farther
away than the planets. Distance between stars varies New length
unit created to measure the distance of the stars: light-years The
distance light travels in 1 year About 9.46 trillion
kilometers
Slide 20
The Doppler Effect The effect produced when a source of waves
is moving with respect to the observer
Slide 21
Doppler Effect (cont.) Happens with all types of waves water,
sound, light Happens with light sources in the universe
Slide 22
Redshift Galaxies Are moving quickly away from Earth Appear red
because of the Doppler effect
Slide 23
Blueshift Galaxies Are moving quickly toward Earth Appear blue
because of the Doppler effect
Slide 24
An Expanding Universe Discovered by Edwin Hubble Light from all
galaxies except those close to us is affected by redshift Galaxies
are moving away from each other, so the universe is expanding