Transcript The Evolutionary Cycle of Stars

THE EVOLUTIONARY
CYCLE OF STARS
CYCLE OF STARS
The 3 major interests (or parameters) of
astronomers are their mass, luminosity, their
surface temperature & distance they are away
from us.
 They are also used to place stars into an
evolutionary sequence which describes their
formation, life & death.
 “Luminosity” of a star is a function of its radius &
effective temperature.
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THE HERTZSPRUNG-RUSSELL DIAGRAM
FOUR MAIN GROUPINGS
“MAIN SEQUENCE STARS”
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It is a defined curved trend across the center
of the diagram which displays a relationship
between mass & luminosity
FOUR MAIN GROUPINGS
“RED GIANTS”
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They are stars which are cooler, but more
luminous than stars on the main trend.
FOUR MAIN GROUPINGS
“SUPER GIANTS”
Most massive of all stars.
 Short life spans.
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FOUR MAIN GROUPINGS
“WHITE DWARFS”
 This
is the last stage of stellar evolution.
BIRTH-LIFE-DEATH
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A giant molecular cloud contains H at low temperatures. This is a
NEBULA(e) that contains gas & dust from the beginnings of a
star. Cosmic cloud of gas & dust, basic building blocks of the
universe, & the largest objects in the universe.
Temperatures rise, driven by gravitational collapse, and a
PROTOSTAR forms. It is the early stage in star formation.
The star evolves & becomes part of the Main sequence of stars.
The star eventually converts into a Red Giant & expands to up to
100 times the diameter of the original star. Red Giants develop
as the hydrogen in the core is depleted.
White Dwarf The final evolutionary state whose mass is not too
high. This is the last stage of stellar evolution.
Super Nova
 is a stellar explosion that creates an extremely luminous
object. A supernova causes a burst of radiation that
may briefly outshine its entire host galaxy before fading
from view over several weeks or months.
 The explosion expels much or all of a star's material
Black Hole
 They are formed
from the cores of
super massive stars
and can best be
described as regions
of space where so
much mass is
concentrated that
nothing, not even
light, can escape the
gravitational pull.
Dark Matter
Scientists estimate that what we do see
may only account for 10% of the mass
of the universe. That means that 90%
of the matter is invisible. Some
estimates even place this number as
high as 99%. Astronomers refer to this
invisible mass as dark matter.