Download Star- large ball of gas held together by large ball of gas held

Stars
Star- large ball of gas held together by
Stargravity that produces tremendous amounts
of energy and shines
Sun-- our closest star
Sun
Star Formation
A cloud of gas and
dust,, called a nebula,
dust
begins spinning &
heating up.
Eventually, it gets hot
enough for fusion to
take place, and a
protostar is born.
Star Formation
In the star’s core, two
hydrogen atoms
collide and fuse
together to make a
new helium atom,
releasing huge
amounts of energy
and making the star
expand.
Energy Production in Stars
Nuclear fusionfusion- the combining of the
nuclei of smaller elements to form the
nuclei of larger elements with some of the
mass being converted to energy
Ex: hydrogen + hydrogen = helium + energy
Sun
The sun is a mass of incandescent gas,
a gigantic nuclear furnace.
Where hydrogen is built into helium at a
temperature of millions of degrees.
Typical Star Composition
Element Abundance (% of total
Abundance
(% of total mass)
number of atoms)
Hydrogen
91.2
71.0
27.1
Helium
8.7
Oxygen
0.078
0.97
Carbon
0.043
0.40
Nitrogen
0.0088
0.096
Silicon
0.0045
0.099
0.0038
0.076
Magnesium
Neon
0.0035
0.058
Iron
0.030
0.014
Sulfur
0.015
0.04
Star Origin and Evolution
1.
2.
3.
4.
Stars originate from clouds of gas and dust
molecules that clump up due to gravity.
When the clump reaches the size of Jupiter, it
creates enough energy by nuclear fusion to
shine – becoming a star.
For stars that are about the size of our sun,
after main sequence they become giants,
white dwarfs, and then black dwarfs.
For stars larger than our sun, after main
sequence and giant stage, they explode in
supernovas, then become either black holes or
neutron stars.
Star Classification
Luminosity: the actual brightness of a star;
Luminosity:
depends on size & temperature
Bigger is brighter
Hotter is brighter
Absolute Magnitude:
Magnitude: a measure of how bright
a star would be if all stars were at the same
distance from Earth
Apparent Magnitude:
Magnitude: a measure of how bright
a star appears to be to an observer on Earth
Depends on distance – closer is brighter
Star Types and Sizes
Size- MOST stars are much larger than Earth
Size1. Main Sequence Stars
Stars-- average
temperature and luminosity stars
90% of stars are main sequence (our sun is
one)
Majority of a star’s lifetime
Use up their hydrogen & helium, producing
heavier elements
Length depends on amount of fuel
Massive stars burn faster – die faster
Star Types and Sizes
2.
Giant or Supergiant (depends on mass)
Star has used up its fuel, so energy
produced cannot counteract force of gravity
& the star’s core collapses
collapses,, while the outer
layers expand rapidly
Giant - low temperature, high luminosity, red,
orange, yellow in color, older than main
sequence stars
Super GiantsGiants- very high luminosity, blue is the
largest, explode into a supernova
Star Life Cycle
Nebula
Main Sequence Star
smaller stars
Giant Star
larger stars
Super Giant Star
Star Life Cycle
3.
White Dwarf (if <10
<10 solar masses)
4.
outer layers from giant stage dissipate,
leaving only a small core
when finishes burning, becomes black
dwarf (dead star)
High temperature, low luminosity
Supernova (if >10
>10 solar masses)
cataclysmic collapse of massive
supergiant, creating intense explosion
forms iron & heaviest elements in last
seconds before becoming either...
Outward
Pressure stops
when Fe fuses
Gravitational
Collapse Begins
Star Life Cycle
Nebula
Main Sequence Star
smaller stars
larger stars
Giant Star
Supergiant
White Dwarf
Supernova
Star Life Cycle
5.
Neutron Star (10
(10--20 solar masses)
6.
supernova collapses into core 6-20km in
diameter, but more massive than our sun
so dense, 1 teaspoon weighs a hundred
million tons!
Occasionally spins to become a pulsar
Black hole (20+ solar masses)
supernova implodes into a supersuper-tiny,
super--massive ‘hole’ that sucks matter &
super
light towards it
Nebula
Main Sequence Star
Smaller stars
Larger stars
Giant Star
Supergiant
White Dwarf
Supernova
massive stars
Neutron Star
Super-massive stars
Black Hole
Star Life Cycle
Nebula
Main Sequence Star
smaller stars
larger stars
Giant Star
Supergiant
White Dwarf
Supernova
massive stars
Neutron Star
super-massive stars
Black Hole
Star Types and Sizes
Life Cycle of a Star
(our Sun now)
The Luminosity And Temperature
of Stars Diagram
Hertzsprung-Russell diagram groups stars
Hertzsprungby temperature and luminosity (also called
HR Diagram)
LARGER
cooler
hotter
SMALLER
H-R Diagram
As you move up the diagram, the objects
become brighter & larger.
larger.
As you move down the diagram, objects
become smaller & dimmer
dimmer..
Moving to the left on this diagram, the
temperature increases.
increases.
Moving right, the temperature decreases
How do we know?
SPECTROSCOPY – the study of light
light,,
breaking it into the spectrum & analyzing
the result, giving us the physical
properties of a distant object
Composition
Mass
(what elements are in it) Brightness
Temperature
Movement
Light Spectrum
Spectroscope
Sample Spectra