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The Sun
Sun
• Considered a medium
STAR
• 93,000,000 miles
away from Earth
• 1.39 million
kilometers in diameter
(one million Earths
can fit inside the sun
• State of matter plasma
More on the Sun
• Contains 99% of
mass of our solar
system
• Made of 82%
hydrogen, 17%
helium, 1% other
Our Sun compared to other suns!
Our Sun compared to other even larger suns!
The sun’s structure
• Core – 27 million degrees
Fahrenheit, where
thermonuclear fusion
occurs
• Photosphere – innermost
part of sun’s atmosphere
but still visible to us,
made of hydrogen gas
that burns at 9000
degrees Fahrenheit –
causes it to glow yellow
The sun’s structure
• Chromosphere –
inner atmosphere,
region of glowing gas;
red color caused by
ionization of hydrogen
• Corona – outer
atmosphere, thin
layer of gas that
extends millions of km
beyond
chromosphere
The sun’s corona
Thermonuclear fusion
• The sun is so bright because it goes
through thermonuclear fusion – when
hydrogen atoms get turned into helium
atoms due to high heat and pressure
– Releases massive amounts of heat and light
as a byproduct
– This energy and light released from the sun
takes 8 minutes to reach us
What is a sunspot?
• An area on the sun that
has extremely strong
magnetic activity
• The magnetic activity
does NOT allow
convection so it is a cool
region
• Looks like a dark spot
• Lasts 2 weeks and only
occurs in 11 year cycles
Magnetic fields
Sunspot activity since 1760
Recent sunspot activity
2013
• We are still in solar maximum. What is happening?
What else should we know about
sunspots?
• They can cause solar
flares
– When hot gases erupt
from the surface of the
sun sending ions and
radiation into space
Solar flares create solar
winds
Solar Flares
Close Up of Flares
Solar prominence
• Streamers of hot
gases arching above
photosphere
• Do not disrupt Earth’s
communications
Solar winds
• Every 11 years, the suns magnetic poles
reverse and release energy
– Billions of tons of particles fire into space at 1
million mph, at the peak it is called the solar
maximum, speeds can reach 3 million mph
– We are in a solar maximum now
Solar Wind – a continuous flow of electrons and
protons from the sun into space
How is Earth protected?
• Magnetospheremagnetic field that is
surrounding the Earth
• Without the magnetic
field, the solar winds
would be much more
dangerous
Earth’s Magnetosphere
Solar Flares in the news
Why does this matter?
• Strong solar flares and
sunspots can damage our
communication systems
and electrical systems
• Also increase aurora
activity
• Aurora Borealis and
Australis – lights caused
by interactions of atomic
particles between solar
wind and the ionosphere
Effect of solar flares and solar
winds
• http://www.teachersdomain.org/resource/e
ss05.sci.ess.eiu.solarwind/
• https://www.youtube.com/watch?v=Hueen
7jPi0w
SDO (solar
dynamics
observatory)
• AIA images the outer
layer of the Sun's
atmosphere (corona) at
temperatures from 20
thousand to 20 million
degrees.
• EVE keeps track of the
extreme ultraviolet (EUV)
rays that the Sun sends
towards us. UV rays
cause skin cancer.
Extreme UV rays are
even more dangerous.
Our atmosphere absorbs
UV, keeping us safe.
• HMI will measure the
ripples and the magnetic
fields on the surface of
the Sun (photosphere) to
determine what is
happening on the inside.
Photo taken
in extreme
ultraviolet
on March
30, 2010 by
the Solar
Dynamics
Observatory
that was
launched by
NASA on
February 11,
2010.
SDO photograph