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Sun PowerPoint - LPI - Lunar and Planetary Institute

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Sun and
Photo from
Created by the Lunar and Planetary Institute
For Educational Use Only
LPI is not responsible for the ways in which this powerpoint may be used or altered.
What are we going to cover
• Properties of the Sun
• Influence on Earth:
– Gravity
– Light
– Solar wind
• Life cycle of the Sun
• Seasons
Photo from
The Sun
• Is a star
• Made of gases
70% hydrogen and 28% helium
• Is our primary
source of energy
Light (radiation)
Image at
How Big is the Sun?
Activity: Let’s measure the Sun
How Big is the Sun?
About 110 times
wider than Earth
1.3 million times
bigger than
Photo from
How does our Sun compare to other Stars?
• Active stars range in
size from supergiants to
• Stars range from very
bright (supergiants) to
very dim (dwarfs)
• Stars range from very
hot blue on the outside
(O class) to cool red on
the outside (M class)
Our Sun is a dwarf—medium
Our Sun is a medium-bright
Our Sun is in-between--yellow
So is our Sun an average star?
• No—most stars are smaller and cooler than our Sun
• Most of the bright stars we see are bigger and hotter
High cadence solar rotation, EIT 195Е (Dec. 10-24, 1999) Movie at
At the equator, the Sun rotates once every 25.4 days
Near its poles, the Sun rotates once every 36 days
Known as “differential rotation”
Sun’s Magnetic Field
• Winds up due to differential rotation
• Eventually forms loops and becomes tangled
Animation of how the Sun's magnetic field winds up and loops out.
Movie at
Inside the Sun
• Core
• Radiative Zone
• Convection zone
Image at
The Sun’s Atmosphere
• Photosphere
• Chromosphere
• Corona
Photosphere image:
Chromosphere image:
Corona image:
Energy from the Sun
Nuclear chain reaction (hydrogen forming
Releases radiation (gamma rays)
The gamma ray loses energy as it bounces
around inside the Sun
It is finally released at the photosphere,
primarily as visible light
Image at
Features in the Photosphere
• Sunspots
– Dark and small (but brighter than Full Moon and big
as Earth)
– Cool-- temperatures only 6,200 F (Sun’s surface is
10,000 F)
– Associated with magnetic fields: one set of spots is
positive, other is negative
Image at
More on Sunspots
• Our Sun has an activity cycle of
11 years
• Sunspots appear at specific
latitudes on Sun
– Bands of latitude move towards
equator during cycle
Images at
uestion17.html and
Solar Events
• Flares (Explosions of energy on the
surface of the Sun)
• Prominences
• Coronal Mass Ejections (massive clouds
of plasma ejected from the Sun)
Movie: Six months with EIT 171 (Aug. 12, 2003 - Feb. 9,
Solar Wind
• Blows charged particles and magnetic fields away from the Sun
• Charged particles captured by Earth’s magnetic field
• Create Auroras or Northern and Southern Lights
Image at
• Electrons from solar wind are captured by the Earth’s magnetic field
• Interact with atoms in our atmosphere: oxygen and nitrogen make red
and green; nitrogen can also make violet
• Northern lights are Aurora Borealis, while southern are Aurora Australis
Animation of solar wind impacting the magnetosphere
and creating aurora
Coronal Mass Ejection
This series of images of coronal mass ejections taken with
LASCO C3 (May 1-31, 1997) at
The eruption of a huge bubble of hot gas from the Sun
CME’s effects on Earth
• Can damage satellites
• Very dangerous to astronauts
• Power problems
Animation of a CME leaving the Sun,
slamming into our magnetosphere.
• Let’s go observe the Sun
• Sunspot graphing
Influences on Earth
• Gravity
• Light (Radiation)
• Solar Wind (already discussed)
• Orbits
– The Sun’s powerful gravity keeps
the planets in orbit
• Our Sun (and all active stars) emits radiation
– Radio, infrared, visible, ultraviolet, x-ray and even some
gamma rays
– Most of the sunlight is yellow-green visible light or close to it
The Sun at X-ray wavelengths
Image and info at and
Activities on Sunlight
• UV Man (or woman, or dog, bug, etc.)
• Observations of infrared light using filters and cell
Sun’s Radiation at Earth
• The Earth’s atmosphere filters out some frequencies
– Ozone layer protects us from some ultra-violet, and most xrays and gamma rays
– Water and oxygen absorb some radio waves
– Water vapor, carbon dioxide, and ozone absorbs some
Electromagnetic spectrum
Sunlight is absorbed by Earth
Let’s test what happens to the light.
Activity Time!!
Sunlight is absorbed by Earth
• The Sun does NOT send “heat rays” into space.
Some of its light is infrared, but that is not the same
thing as heat.
• The Sun’s light is absorbed by Earth (clouds, plants,
oceans, rock…)
• By absorbing the light, we are transforming it into
heat energy
Sun as a Source of Energy
• Light from the Sun is absorbed by the Earth,
unevenly to:
– drive wind bands – which drive surface currents
– drive deep ocean currents
– drive water cycle
– drive weather
NASA image at
Credit: NASA GSFC Water and Energy Cycle
Sun as a Source of Energy
• Plants need light for photosynthesis
• Without its heat, the only inhabitable areas on Earth
would be near volcanic vents
Images from and
stars form
in nebulae
from Small
Magellanic Cloud
Image at
Star-forming region in the Large Magellanic Cloud:
Orion image at
Our Sun is a Regular/ Small Star
Image at
In a few Billion years… Red Giant
Image at
Our Sun’s Habitable Zone
Billions of years ago, things may
have been different
– The Sun was cooler (by up to
– Earth’s atmosphere was
different (thicker, carbon
Animation at
Conditions will be different in
the future
– By many accounts, increases in
the Sun’s temperature will make
Earth uninhabitable in 1 billion
years or less
– These changes will also affect
other planets… Mars?
By 5 billion years… White Dwarf
Image at
Image at
Image at
Stars are
Image from
Image from
Supernova—Massive Star Explodes
Images at
Done with the Sun
• Time for Seasons!
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