Transcript 4.1 – 4.3 - s3.amazonaws.com

4.1 – 4.3
What is space like?
• No air – vacuum
• No air friction – force
that resists motion
• Mostly black – absence
of light
• Extreme temperatures
Galactic Shapes
• spiral galaxies
–include the Milky Way (our galaxy)
–all have a central nucleus
• have long curved arms
–contain a lot of gas and dust
–barred spirals
• the spiral arms are attached to a straight
“bar” that runs through the center of the
galaxy
• Spiral
• Barred Spiral
Barred Spiral Galaxy
• elliptical galaxies
–resemble an egg or a football
–not as structured
• irregular galaxies
–groups of stars that have no
defined shapes
–the Large Magellanic Cloud and
Small Magellanic Cloud
»the two closest galaxies to ours
• Elliptical galaxy
• Irregular galaxy
• Celestial Clouds
• nebulae
–large clouds of gas and dust
floating in space
–They are most common in spiral
and irregular galaxies
–horse head nebula is one of the
most widely known nebulae
Helix Nebula
• Horsehead
nebula
Constellations
»Group of stars outlining an imaginary
picture
»most have been identified since
ancient times
»Constellations were once used to
navigate by travelers because they
appear to revolve around the North
Star
»They are also used to refer to 88 regions of
the sky (celestial sphere)
•North Star
–Polaris is the scientific name for the
north star
–It is located directly above the Earth’s
“axis of rotation”
»The axis is the Imaginary line that
runs from the north pole to the
south pole on which the Earth spins
»The word constellation has two current meanings
-The oldest refers to a pattern of stars
-The reference used by most current
astronomers refers to a section of sky.
-We will look at some of the patterns or
arrangements of stars.
»The constellations seen in the Northern
Hemisphere are divided into groups
determined by the season in which people can
see them. So we call them:
»Spring constellations
»Autumn constellations
• 2 groups in the northern hemisphere
– Spring Constellations
– Autumnal Constellation
Constellations of the Northern
Hemisphere
–Ursa Major
•The Great Bear
•Contains the Big Dipper
–Most familiar of all
constellations
• Ursa Minor
–The Little Bear
–More commonly called the Little
Dipper
–Polaris is at the point of Ursa
Minor
• Queen Cassiopeia
–Named after a mythical queen of
Ethiopia
–Looks like a big “M” or “W”
• King Cepheus
–Looks like a house with a long
pointed roof
– Andromeda
• Mythological daughter of Cassiopeia and
Cepheus
• Andromeda is also called “The Lady in Chains”
• Her head is part of the Great Square star
formation
• Contains the Andromeda Galaxy
– Whale
• Monster that was to devour Andromeda
• This constellation is often located beneath the
horizon