Download 14 - Sitka School District

14.4 Stars and Galaxies
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Sun is the closest star to use and its light blocks out the light from the other
stars during the day so we don’t see them.
Constellation-group of stars that form patterns in the sky
Stars come in different masses, sizes and temperatures
Color tells temperature
o Red are coolest
o Yellow are medium (like our sun)
o Bluish-white are the hottest
Betelgeuse, a giant red star, would swallow Mercury, Venus, Earth and Mars if
it sat in the same place as our sun!
The 4 steps in the formation of a star are below
Start as
huge
clouds of
gas & dust
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Force of
Gravity causes
clouds to
compress
Compression
causes
temperature to
rise
When it is dense
enough & hot
enough, the star is
formed
GIANT stars form when a medium sized star (like the sun) uses up some of the
gases in its center and expands. Once the remaining gases are used up it
contracts to become a BLACK DWARF.
SUPERGIANTS are formed when a huge star uses up the gases in its core.
When the core of a supergiant collapses the outer part explodes and gets
bright, this is known as a SUPERNOVA.
o The supernova may shine brighter than a whole galaxy for a few days
and the dust and gases that are released become new stars
o The core is called a NEUTRON star and if it is large enough may
become a BLACK HOLE which are so dense that any light shone into
them disappears.
GALXY is a group of stars, gas and dust held together by gravity
Light-years are used to measure distances between galaxies
o Distance light travels in one year = 9.5 trillion km
o Light travels so fast it could go around the earth 7 times in 1 sec
Milky Way Galaxy
o Our galaxy
o Trillions of stars
o Our sun revolves around the Milky Way once every 240 million years
May be up to 100 billion galaxies
All of the galaxies make up the universe