types of galaxies. what is a galaxy? a giant cluster of stars, gases,and dust held together by...
TRANSCRIPT
Types of Galaxies
What is a galaxy?• A giant cluster of stars, gases,and
dust held together by gravity.• Contains hundreds of billions of stars• Three shape classifications:
SpiralEllipticalIrregular
Spiral Galaxy• Shaped like a flattened
disk with a bulging center and “arms” that curve in a spiral pattern
• Rich with dust and gases
• Form new stars (mostly in dense material of “arms”)
• Center bulge is made up of old stars
•
Milky Way
• The name of the galaxy where our solar system is located.
• It is a “barred” spiral with a dense “bar” of stars at the center from which the arms branch out.
• This is a drawing, not a real picture as we do not have probes outside our galaxy to take the pictures.
•
Elliptical Galaxy• Shaped like a sphere
or “egg”• Most stars are old
stars• Very little gas and
dust• Stars are close
together near center• Stars on outside edge
are farther apart
Irregular Galaxy• No definite shape
or organization• Contain a mix of
old stars, new stars, clouds of dust and gases
The Local Group
The Big Bang Theory
• The most popular theory explaining the beginning of our Universe and everything in it.
• The idea that the universe began as a tiny, very hot point or “singularity” and began to expand rapidly, then cool.
• Still continuing to expand (like a tiny balloon that expands, but never pops).
Homework
• You will write a “Step-Up-To-Writing” style summary paragraph. The topic sentence is : “Galaxies can be classified as spiral, elliptical or irregular.”
• Your paragraph should be at least 8 sentences.
• Topic sentence should be followed by a yellow detail sentence then a red example sentence (repeat until you have at least 3 yellow sentences and a red for each). End with a green conclusion sentence.