Astronomy 2: Sun and Energy;

1. ASTRONOMY 2
The Sun & Energy
ppt by Robin D. Seamon
1

2. 2
SUN
VOCABULARY:
solar flare
sunspot
nuclear fusion
nuclear fission
protostar
main sequence star
red giant
neutron star
Black Hole
planetary blue nebula
heavy elements

3. 3
THE SUN

4. 4
Sunspot: cooler spot
on Sun as seen through
a filter
Solar Flare:
explosion on the
surface as seen
through a filter

5. 5
Sun is a giant ball of burning gas.
70% Hydrogen
28 % Helium
Carbon, Nitrogen, Oxygen
Nuclear fusion:
Hydrogen atoms get squeezed so tightly by gravity
that their nuclei fuse together to form helium.
• 4 Hydrogen fuse into 1 Helium atom
(The process uses up 2 of the protons in the form
of light)
• Releases a tremendous amount of energy

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Nuclear fusion nuclear reaction in which
atomic nuclei of low atomic number fuse to
form a heavier nucleus with the release of
tremendous energy.
Nuclear fission: the nuclei of atoms are split,
releasing tremendous explosive energy; we
can do this in Power Plants to heat water for
the generators (to produce electricity.)
ENERGY REVIEW

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Life Cycle of a Star
• A star is formed in clouds of dust & gas called
a nebula
• The lifetime of a star depends on its size

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The larger the star, the shorter its lifetime…
1. Hydrogen gas in the nebula pulls together &
begins to spin.
2. It spins faster to become a protostar.
3. When temperatures reach 15,000,000
degrees, nuclear fusion combines Hydrogen
into Helium. It glows brightly & becomes
stable. (main sequence star)
4. Star will remain a main sequence star for
millions to billions of years.
OUR SUN!

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5. As the Hydrogen runs out, its core shrinks &
becomes unstable. Its outer core expands.
6. As the outer core expands it cools
becomes red. (red giant phase)
7. In the core of the red giant, Helium fuses
into Carbon.
THE NEXT STEP IS DETERMINED BY HOW BIG
THE STAR WAS TO BEGIN WITH…

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FOR MASSIVE STARS
6. After red giant, star
explodes in a supernova
7. If small after the
explosion, it can become a
neutron star. If 3 X size of
the Sun, the force of its
gravity will pull itself
together into a Black Hole
- Black Holes readily
attracts & ‘swallows’ any
matter & energy that
comes near it
FOR SMALLER STARS
6. After Helium fuses into
Carbon, the core
collapses again & outer
layers are expelled.
7. A planetary blue nebula
is formed by outer
layers. The core
remains a white
dwarf, cooling
eventually to a white
dwarf.
OUR SUN!10X or more size of the Sun

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FOR MASSIVE STARS
-- The supernova explosion creates the heavier
elements in the Universe.
10X or more size of the Sun

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Credit:ImagecreatedbytheEuropean
SouthernObservatory.

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SUN & ENERGY
VOCABULARY:
thermal radiation autotroph
electromagnetic radiation solar cells
electromagnetic spectrum solar water heating
conduction solar furnace
convection solar wind
radiation aurora
wavelength atmosphere
frequency greenhouse gas layer
infrared radiation ozone layer
Earth’s bulge
Milankovich Cycles
precession
nutation
photosynthesis

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The SUN supply Earth’s Energy.
Thermal radiation: means of energy transfer
between the sun and the Earth (heat & light)
HOW?
Electromagnetic radiation form of energy that
can be reflected or radiated through space; no
matter is involved; moves thermal radiation from
one place to another
EM: (have characteristics of magnetic & electrical
energy)

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Thermal Energy
• Amount of Energy an object has due to the
movement of its molecules
• Can be transferred from one object to another
through:
• conduction (if objects are touching)
• Convection (warm goes up/cold goes
down; Sun heats air and water currents
on Earth)
• Radiation (infrared radiation from the
sun carried by electromagnetic waves in
pockets of light called photons)
ENERGY REVIEW

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ELECTROMAGNETIC SPECTRUM
• Wavelength: distance between crests of a
wave
• Frequency: number of cycles within a period
of time
PHOTON

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• Gamma radiation ,x-rays, UV rays: blocked by
Earth’s upper atmosphere
• Visible light: observable on Earth
• Infrared radiation: absorbed by Earth’s
atmosphere
• Short-wave Radio waves- observable on Earth
• Long-wave Radio waves: blocked by our
atmosphere

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Electromagnetic spectrum

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Thermal radiation: absorption on Earth
• Infrared radiation (heat) affects land water,
& air differently
• land changes temperature faster than water
or air
• 71% Earth covered in water
• convection currents move the air & water
through the atmosphere & hydrosphere
respectively

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DISCUSS:
Differential heating of surfaces
Causes of weather & climate
Erosion
Factors into the water cycle
How does the
sun contribute
to the
following:

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REMEMBER:
variations in the directness of the sun’s rays,
controls the amount of thermal Energy that
reaches the Earth at any given location.
Let’s look at other astronomical factors that
influence the distribution of thermal Energy
from the Sun to our planet…

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A NOTE ON SHAPE: Earth’s Bulge
Earth is fatter than it is tall (b/c of the spin &
gravity towards the sun)

26. (ASTRONOMICAL VARIATIONS that affect Earth’s
long-term climate cycles)
Milankovitch Cycle variation in intensity of
sunlight due to slight variation in Earth’s orbit
• Pace setter for cycles of warming & cooling
cycles

27. http://www.bgs.ac.uk/discoveringGeology/climateChange/ge
neral/causes.html?src=topNav
http://www.southwestclimatechan
ge.org/figures/milankovitch
Orbital shape:
(eccentricity)
Earth’s orbit changes
from it’s elliptical
shape; 100,000 yrs
Orbital axis
precession: (wobble)
caused by Sun & Moon’s
gravity on Earth’s bulge)
Changes in tilt causes
strength of seasons
26,000 years
VIDEO: Orbital Forcing (1 min)

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Orbital axis nutation:
• because the moon is also spinning, there is a
slight variation in the gravitational pull on
Earth throughout a month.
• 18 yr period

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ASTRONOMICAL CLIMATE Influencers:
• Earth’s axis tilt
• Earth’s revolution around the sun
• Precession
• Nutation
• Eccentricity

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The Sun also controls LIFE on Earth
• Supplies the energy for photosynthesis for
autotrophs to begin the food chain

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HOW we can harness the Energy:
Solar cells: solar panels gather light energy
generating DC current. It’s then converted to
electrical energy (AC current) in a solar inverter

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HOW we can harness the Energy:
Solar water heating: fluid is circulated & heated in
solar cells then passed through water storage,
transferring heat

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HOW we can harness the Energy:
Solar furnaces: structure that captures sunlight
with an array of curved mirrors to produce very
high temperatures

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Sun emits electromagnetic radiation in all
directions but… Not all radiation reaches Earth
• Solar Wind subatomic particles (protons &
electrons) ejected from the sun
• Auroras interaction of solar wind particles
with Earth’s upper atmosphere & magnetic
field causes colorful waves of light over the
poles

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Solar Wind

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Aurora borealis
Aurora australis

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• Atmosphere gas layer on Earth; blocks or
traps some of the sun’s solar energy
• Greenhouse gas layer: traps thermal
energy on the planet
• Ozone layer: blocks sun’s harmful UV
rays