Transcript File star characteristics and life cyclesx

STAR CHARACTERISTICS AND LIFE CYCLES
HOW ARE STARS CLASSIFIED?
• Characteristics used to classify stars include:
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Color
Temperature
Size
Chemical composition
Brightness
COLOR AND TEMPERATURE
• A star’s color reveals its
surface temperature.
• Blue stars are the hottest
(about 35,000OC), red stars
are the coolest (about
3000OC), and yellow stars like
our sun are about 5,500OC
SIZE
• Many stars are about the same size as the sun,
which is a medium-sized star.
• Most stars are smaller than the sun.
CHEMICAL COMPOSITION
• Stars vary in their composition, but most are similar to that
of the sun: about 73% hydrogen, 25% helium, and 2% other
elements.
• Since every chemical element has a characteristic spectrum
in a given range of temperatures, the colors and lines in the
spectrum of a star indicate the elements that make up the
star.
BRIGHTNESS
• The brightness of a star depends on both its size
and temperature.
• A star’s apparent brightness is its brightness as
seen from Earth (stars closer to Earth appear
brighter).
• A star’s absolute brightness is the brightness the
star would have if it were at a standard distance
from Earth.
H-R DIAGRAM
• Astronomers use a HertzsprungRussell diagram, or H-R diagram,
to classify stars and to understand
how stars change over time.
• This diagram shows the absolute
brightness and surface
temperatures of stars.
• Most stars are located on the
diagonal area called the main
sequence, which are stars similar
to our sun.
DRAW STAR LIFE CYCLE WITH NOTES ON
BOARD!
STAR LIFE CYCLE VIDEO
• https://www.youtube.com/watch?v=PM9CQDlQI0A