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The Story so Far....
1964
t = +380,000 years
The Story so Far....
t = +600 million years
1964
Galaxy Detected!
?
udfy-38135539
z=8.6
WMAP
The Story so Far....
t = ~1 billion years
1964
Large Scale Structure
?
WMAP
The Story so Far....
t = +13.73 billion years
1964
?
WMAP
The Story so Far....
t = +13.73 billion years
1964
?
• Structure?
• Elements?
WMAP
The Story so Far....
1964
Structure in Early Universe:
•Matter concentrated (WMAP)
•Formed protogalactic clouds
•Clouds collapsed & fragmented
to form stars & galaxies
STARS are the basic units
of structure in the Universe!!
Galactic Recycling
ALL HEAVY ELEMENTS
ARE FORMED DEEP
INSIDE STARS!
PRESSURE
Star Formation:
The Great Battle
Between....
GRAVITY
GRAVITY
(Newton’s Law of Gravity)
Thermal Pressure:
Depends on Density and
Temperature
Thermal Energy:
Kinetic Energy of
Particles
PRESSURE
Temperature:
Measures AVERAGE Kinetic
Energy of Particles
The Interstellar Medium (ISM)
Gas (99%) and dust (1%) in between stars
Stars form in DENSE regions of the ISM....
Current Composition:
70% H, 28% He, 2% Heavy Elements
The Interstellar Medium (ISM)
Gas (99%) and dust (1%) in between stars
Stars form in DENSE regions of the ISM....
Early Composition:
75% H, 25% He, 0% Heavy Elements
GIANT MOLECULAR CLOUDS (GMCs)
Large, Dense, & Cold regions of ISM
GMCs are dense RELATIVE to ISM
Made of Molecular Gas & Dust
Avg. Densities:
ISM: 1 atom/cc
GMC: 100-1000 atoms/cc
(Air: 30 billion billion molecules/cc)
GIANT MOLECULAR CLOUDS (GMCs)
Large, Dense, & Cold regions of ISM
GMCs are the LARGEST structures in Galaxy
0.1-10 million solar masses
Why so big???
GRAVITY
•Cloud Core Collapses due to GRAVITY
Density
Gas Particle Energies
Temperature
GRAVITY
FUSION!!
• Stellar Nucleosynthesis, Phase 1: H-Burning
•(H into He, MAIN SEQUENCE)
• Generates Energy & Provides Pressure!
PRESSURE
Fusion in Stars
Lighter Nuclei combine to produce Heavier Nuclei:
• Only process capable of producing required energies
to hold up the star against gravity!
Mass of 4 H Atoms = 6.693 × 10-27 kg
Mass of
1 He Atom
= 10-27 kg
Annual
output
of6.645
Sun× =
Difference
Annual
-27 kg
=
0.048
×
10
energy used by
Vegas every second
Mass “lost” (0.7%) is converted to Energy!
since the Big Bang!
How much energy?
PRESSURE
GRAVITY
STAR IS NOW
STABLE -Hydrostatic Equilibrium
-- balance between
gravity & pressure
The Sun is a Mass of Incandescent Gas...
Incandescence:
Heat-driven light emission...
...random energies for particle
collisions leads to
CONTINUOUS SPECTRUM
Solar Structure - 4 (+) parts
Convection zone
1. Core
T~1 Million K
and less
2. Radiative Zone
3. Convection Zone
4. Photosphere
Outer layers
(Atmosphere)
T=13.6 Million K
Radiative zone
T~2-7 Million
Photosphere+
Keep spectra in mind - Continuous, Absorption, Emission
The Sun is HOT...
(The Sun Is So Hot That
Everything On It Is A Gas)
X
The Sun is a Mass of
Incandescent Gas...
X
core is 13,600,000 K
PLASMA - ions
& free electrons
miasma of plasma!!
Solar Structure - CORE
...a Gigantic Nuclear Furnace
(where Hydrogen Is Built Into Helium
at a Temperature Of Millions Of Degrees)
Energy is Generated in the CORE
4H
core is > 10,000,000 K
The Proton-Proton
Chain
 9.2 x 1037
He
reactions per
second!
Solar Structure - CORE
...a Gigantic Nuclear Furnace
(where Hydrogen Is Built Into Helium
at a Temperature Of Millions Of Degrees)
(you don’t need to know numbers, just the idea below)
Mass of 4 H Atoms = 6.693 × 10-24 g
Mass of 1 He Atom = 6.645 × 10-24 g
Difference
= 0.048 × 10-24 g
Mass “lost” (0.7%) is converted to Energy!
 9.2 x 1037 reactions per second!
 A little mass yields A LOT of energy:
1 gram of matter ⇒ 1014 Joules (J) of energy
(powers a 100 Watt light bulb for ~32,000 years!)
Sun: 90 billion Megatons TNT/second !!
E=mc2
Albert Einstein
1905
Solar Structure - Radiative Zone
ENERGY
TRANSPORT BY
RADIATION
Convection zone
T~1 Million K
and less
⇒ions & free electrons
⇒ photons carry energy,
interacting on the way out
“RANDOM WALK”
t ~ 1 million Years!
T=13.6 Million K
Radiative zone
T~2-7 Million
Solar Structure - Convection Zone
Convection zone
COOLER than
Radiative Zone
T~1 Million K
and less
⇒ electrons bound
⇒ photons absorbed
(heat the gas)
⇒ “bubbles” carry energy
out
T=13.6 Million K
Radiative zone
T~2-7 Million
Photosphere: Visible “Surface” of the Sun
MUCH COOLER
Convection zone
T~1 Million K
and less
Teff ~ 5800 K
(Effective Temperature)
T=13.6 Million K
Radiative zone
T~2-7 Million
BASE: CONTINUOUS
SPECTRUM
Sun is a Typical Main Sequence G Star
H-R Diagram:
Luminosity vs.
Temperature for
all stars
Sun: G2 V
T(surface) = 5800K
(yellow)
L = 3.85 x 1026 W