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Life Cycle of a Star
The Night Sky
Ancient observers around the world looked up at
the night sky and imagined groups of starts
formed pictures. We call these imaginary
patterns of stars constellations.
Big Dipper
Orion’s Belt
Classifying Stars
A star is a ball of plasma held together by its own gravity.
Characteristics used to classify stars include color, temperature, size, composition, and brightness.
Ant’s Nebula
Twinkle, Twinkle, Little Star ...
How I Wonder What You Are ...
Stars have Different colors which
indicate different temperatures.
The hotter a star is, the faster it burns its
life away.
O, B, A, F, G, K, M [Oh Be A Feisty Goat, Kick Me]
Characteristics of Stars
A stars magnitude (brightness) depends
upon both its size and temperature.
A stars apparent magnitude is how bright a
star appears to be from Earth
A stars absolute magnitude (luminosity) is
how bright a star actually is.
Swan Nebula Light Echo
Characteristics of Stars
Astronomers use a unit called a light-year to
measure distances between the stars.
In space, light travels at about 186,000 miles per
second.
A light year is the distance that light would travel in a
year or 6,000,000,000,000 (6 trillion) miles.
Measuring Objects in Space
Astronomers use parallax
to measure distances. A
parallax is the apparent
chance in position of an
object when you look at it
from a different place.
Hertzsprung-Russell Diagram L
um
ino
sity
Temperature
An H-R diagram
plots the
luminosity and
temperature of
stars.
Life of a Star
Four types of stars make up the life of
a star
Nebulas
Main Sequence
Giants & Super Giants
White Dwarfs
Stellar Nursery – 1st Stage
Stars begin as clouds of gas and dust called Nebulas that are pulled together by gravity.
Matter in the gas cloud will begin to condense into a dense region called a protostar.
Cat’s Eye Nebula Cone Nebula
Main Sequence – 2nd Stage
Nuclear Fusion begins as the gas cloud becomes hotter and denser beginning the main sequence phase.
While a stars life span depends on its size and temperature, it will spend most of its life in this phase.
Our Sun is currently in
the main sequence
phase.
Red Giants and Supergiants
Eventually, the star's fuel will begin to run out. It will expand into what is known as a red giant. Massive stars will become red supergiants.
This phase will last until the star exhausts its remaining fuel (hydrogen) at this point the star will collapse.
Dwarfs
Most average stars will blow away their outer
atmospheres to form a planetary nebula.
Their cores will remain behind and burn as a
white dwarf until they cool down and all that is
left is a dark ball of matter known as a black
dwarf.
Massive Stars
If the star is massive enough, the collapse will trigger a violent explosion known as a supernova.
Material from the star is left behind creating a neutron star made of nothing but neutrons. Neutron stars spin and send out beams of radiation
called pulsars.
Black Holes
If the mass of the star is large enough, it will collapse so completely that it will literally disappear from the universe creating a Black Hole. Even light cannot escape its gravity.
Astronomers can detect black holes by using X-ray telescopes.
Optical X-ray
Life Cycle of Stars
black dwarf
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