Transcript Stars - EarthScienceLessons

STARS
THINGS YOU NEED TO KNOW ABOUT A
STARS LIFE
The six-seven steps for BOTH low and high mass
stars
 Where do all the other elements (besides
Hyrogen, Helium, and Lithium) come from
 The Fusion Process
 How to read an HR diagram and where the
different parts of a stars life are on the diagram

STAR CLASSIFICATION
O
– Oh
B – Be
A – A
F – Fine
G – Girl
K – Kiss
M – Me
Hottest
Coolest
THE H-R DIAGRAM
1. THE NEBULAR HYPOTHESIS
Lower Mass Star

Gravity pulls gas in
from surrounding
nebula
Higher Mass Star

Same
2. PROTOSTAR – THE “FETUS”
Lower Mass Star
Starts to glow but not
yet truly a star
 Fusion has not yet
started

Higher Mass Star

Same
FUSION
 Nearly
all matter in the universe
started as Hydrogen or Helium (There
was a very tiny bit of lithium)
 No other elements existed until stars were
born
 Fusion is the process by which
lighter elements combine to form
heavier elements
 Fusion gives off an immense amount
of energy for elements lighter than
iron.
FUSION OF H-2 AND H-3

Fusion is the process that causes stars to “burn”
3. MAIN SEQUENCE – YOUTH AND
ADULTHOOD
Lower Mass Star
Begins with Fusion
 Can last between two
to a couple hundred
billion years
 Hydrogen fusion
phase
 A star spends around
80% of its life in this
stage

Higher Mass Star
Begins with Fusion
 Lasts a few million to
a couple billion years
 Hydrogen fusion
phase
 Very high mass stars
can be “giants” such
as a blue giant.

4. GIANT STAGE – OLD AGE
Lower Mass Star

With the beginning of
helium burning, star
swells to a red giant.
Higher Mass Star

With the beginning of
helium burning, the
star swells to a red or
white supergiant
5. PLANETARY NEBULA – PLANETS
DESTROYED
Lower Mass Star

Inner planets are
taken inside the sun
(what doesn’t get
blown away). Outer
(gas) planets are
destroyed by solar
winds from the red
giant.
Higher Mass Star


Any planets that exist
far enough out are
destroyed by solar
winds. But planetary
nebula is fairly
insignificant because of
star size and the death
that soon follows
NOT SIGNIFICANT
FOR HIGH MASS
STARS
6. COLLAPSE AND DYING – THE “DEATH”
BED
Lower Mass Star


After Helium and
possibly carbon/oxygen
burning the star burns
out due to insufficient
heat to continue on to
fusion of heavier
elements
Star collapses into a
white dwarf since there
is no outward pressure
from burning.
Higher Mass Star

After Iron is created
by fusion, the star
burns out and
collapses very quickly,
resulting in a
nova/supernova.
Leaving behind a
neutron star
7. FINAL DEATH – THE GRAVEYARD
Lower Mass Star

Theoretically a white
dwarf will cool until it
no longer gives off
light.
Higher Mass Star

If the star has enough
mass, the neutron star
will collapse further
into a black hole.