Click the mouse to advance
with new images and
information from
NASA/ESA’s SOHO
spacecraft
The Solar and
Heliospheric
Observatory
created by Steele Hill
at Goddard Space Flight Center
Greenbelt, MD
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The Sun as photographed by the
SOHO spacecraft in 1997
The Sun as
revealed in
extreme
ultraviolet light.
Differences in the
Sun’s densities
cause the
uneven
appearance on
its surface.
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The Sun viewed in different ultraviolet wavelengths
The Sun is revealed in
three different
wavelengths, each
one showing cooler
material than the
one before it. These
images were taken
at nearly the same
time on the same
day.
• Note how certain
features are revealed or
hidden in different
wavelengths.
Click on the image to view the clip
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The Sun’s Rotation
Video of the Sun
covering 12 days
shows its rotation
and some regions
of activity. The
Sun rotates about
every 27 days.
The green color is
added so that scientists
can easily know which
filter was used here.
Click on the image to view the clip
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Earth’s size in relation to Sun
The black dot
represents the
approximate size
of the Earth.
Question:
About how many
Earth’s do you
think could fit
inside the Sun?
The Sun is 865,000 miles in diameter or 110 Earths across.
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The parts of the Sun
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Real facts about the Sun
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is 93 million miles from the Earth
1 second of its energy = U.S. energy needs for 90,000 years
light from the Sun gets to the Earth in 8 minutes
consists of 92% Hydrogen, 7% Helium, and 1% other gases
has an 11-year cycle of solar activity
is 5 billion years old, another 5 billion to go
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is a medium-size star, one of about 2 billion in our galaxy
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Fun facts about the Sun
Most of us know that radiant energy from the Sun heats and
lights the Earth, but did you know that:
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The ancient Mayan, Egyptian, and other cultures
worshipped the Sun.
We measure time by and base our calendar on the Sun.
How long does it take for the Earth to go around the Sun?
Answer: 365 days or 1 year
If you drove a car at 100 miles per hour to the Sun, how
many years would it take to get there? 5, 50 or 100.
Answer: About 100 years. Now that’s a long drive!
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Solar Eclipses
Eclipses occur when
the moon blocks our
view of the Sun from
specific areas of the
Earth. Here you see
a relatively rare total
eclipse, which lasted
only about five
minutes or less but
reveals a detailed
view of the corona.
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Stonehenge and the Sun
Stonehenge in England,
built about 3,000 years
ago, is composed of 30
upright stones, each over
ten feet tall, aligned in a
circle, with horizontal
stones perched upon
them. There is also an inner circle composed of similar
stones. A mysterious site, many
believe it served as a prehistoric
astronomical observatory, especially
for charting the Sun’s movements.
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The Sun is the source of all our energy
Every second, millions of protons in the Sun's core collide with
other protons due to powerful pressures to produce helium
nuclei in a fusion reaction that releases energy.
Neutrons + protons
+
Helium nucleus + light and energy
=
Without the Sun’s heat and light,
life on Earth would not be possible.
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What about solar energy?
Solar energy is the least polluting and most inexhaustable of all
energy sources, with great potential but still somewhat costly.
The two most common systems heat buildings and create
electricity. Most spacecraft use solar power for their
instrumentation and communication.
The concept
The reality: solar panels
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Radiation in the Sun’s interior
This animation
illustrates how the
energy created by
the extremely
powerful fusion
process in the Sun’s
core radiates out
through the radiation
zone (bright yellow)
to the convection
zone (gold).
Click on the image to view the clip again
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Convection in the Sun
In the Sun’s outer
layers, matter rises up
and transports its
energy from a hotter,
lower level to a cooler,
higher one. Thus,
there is a constant
circular rising and
falling of gases in its
convection zone.
Illustration of solar convection
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The Solar Corona
The corona is the area
just above the
surface. While the
surface is about
5,000o Celsius, the
temperature in the
corona reaches about
2 million degrees
Celsius. What causes
this rapid increase in
temperature is not
well understood.
5,000 o C
2,000,000 o C
The black circle divides two images.
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Granulation on the Sun’s surface
The Sun’s surface pattern
looks like rice grains. Large
convection cells cause this
granulation, since each cell
has a column of hot gas
rising and cool gas
descending. Granules the
size of Earth and larger
constantly evolve and
change in a churning kind of
motion. This clip represents
about four hours of activity.
Click on the image to view the clip
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Sounds of the Sun
Waves of motion pushing out from within the Sun have
actually been recorded as sound and converted to
audible levels. Since we could not hear them as they
are (too low a sound), they have been greatly raised
in pitch. Listen closely . . .
The Sun hums along!
Click there to play the sound.
(The volume on your computer
must be turned up.)
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What is the solar wind?
A constant stream of particles flows from the Sun’s corona, with a
temperature of about a million degrees and with a velocity of
about 450 kilometers per second. The solar wind reaches out
beyond Pluto's orbit (about 5900 million kilometers). The
drawing shows
how it pushes on
and shapes
the Earth’s
magnetosphere
(the dotted line).
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The Sun’s magnetic field
The Sun is strongly
affected by magnetic
forces. The red arrows
show open magnetic
field lines emerging from
the poles. The gray
arrows represent solar
wind particles which
carry field lines with it.
The bright active regions
have closed magnetic
field lines (orange).
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The Sun’s extended magnetic lines
Some of the Sun’s
magnetic field
lines are closed
(yellow, but
others from the
poles are open
(red. Most are
carried out into
space by the solar
wind (light dotted
lines.
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Sun Spots
Darker and cooler areas are caused by a concentration of
the Sun's magnetic field lines, which last from several
hours to several months. Their frequency varies with the
solar cycle (11 years), in 1997 near its minimum.
Light and dark in this
magnetic scan of the Sun
indicate concentrated
areas of intense
magnetic field lines.
Close-up of sunspots
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Polar coronal holes
Shown with special filters in extreme ultraviolet light (the
green tint is a false color). Hot gas flows out from the
coronal holes (where magnetic field lines are open to
space) into the solar wind.
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Multiple solar prominences
A fairly common occurrence, these eruptions are caused by
magnetic forces. Cooler gases above the photosphere can
often be seen flowing along magnetic field lines.
This is an active
region.
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Prominences and magnetic loops
This image is tinted blue to
identify to scientists which
filter was used to create it.
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Large Solar Prominence
This is the largest
prominence
observed by
SOHO. Twisting
magnetic fields
forced this huge
eruptive
prominence
100,000 kilometers
above the Sun. The
plasma is heated to
about 150,000
degrees C.
28 Earths
high
August 27, 1997
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Video clip showing solar activity
The Sun is surprisingly
active. The motion
captured here occurred
over a 12-hour period.
The sliding movement of
gases follows the lines of
magnetic forces. You can
also see the boiling type
of motion on the surface.
Click on the image to play the video
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Comet Hale-Bopp and Aurora Borealis
Both these dramatic events, rarely seen together, are directly
influenced by the Sun. Keep on going to find out how!
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Comets and the solar wind
By studying the tails of comets,
scientists determined there
must be a solar wind pushing
out from the Sun because the
tails always head away from
the Sun. (Note the comet’s
blue ion tail as well.)
Hale-Bopp
Sun
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Sun grazing comet as it approaches the Sun
A comet is seen
entering from the
lower left streaks
towards the Sun on
Dec. 23, 1996, and is
presumably
consumed by the
heat soon after this
image was taken.
Solar particles can
also be seen blowing
out into space on the
right side.
Click on the image to play the video
The clip spans about 3 days.
Note: the Sun is blocked by a disk but represented by the white circle.
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Auroral Lights
They are also Northern or Southern lights. These often brilliant
and colorful phenomena, seen in the night sky usually closer
to the poles, are caused by the impact of solar wind particles
and magnetic forces on the Earth’s magnetosphere.
Click on this image to play the video
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Aurora as seen from space
Aurora taken from the space shuttle
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Large coronal mass ejection (CME) sequence
CMEs are clouds of million
degree Celsius gases
ejected from the Sun at
hundreds of miles per
second. This one clearly
heads off to the right.
CMEs are caused by the
breaking apart of
magnetic forces. This
sequence occurred over
an 8-hour period in 1996.
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Another CME sequence
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CMEs release a
billion tons of
matter at millions
1
2
3
4
miles/hr.
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CMEs occur almost
every day but few
are Earth-directed
a CME wave, moving
through space, is
preceded by a shock
wave of matter
pushed ahead of it
the bright spot (lower
left in each) is Venus
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CME shown in soft X-rays
This dramatic footage taken by the Yohkoh spacecraft
shows a very strong storm blasting particles out from
the Sun over a 36-hour period.
Click on the image to view the clip again
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Solar flare and CME event
This video of an April 7, 1997 event captures the
dynamics of a solar storm building up then flaring out
over a 4-day period.
Solar flares are "explosions" on the Sun where tensions in the
magnetic field are released. These generate a lot of energy that
heats up material and shoots it into outer space. Solar flares are
usually associated with active regions.
Click on the image to play the video
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Another view of April 7 CME event
This is a “running difference” video sequence where the
imaging highlights the difference between each successive
image so that the changes are easier to visualize. The Sun
is blocked by a disk but represented by the white circle.
Click on the image to play the video
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Animation of a CME approaching Earth
It takes 2 to 4 days for a CME blast to reach Earth, as it
expands up to 30 million miles wide. The white lines represent
the shape of Earth’s magnetosphere (magnetic field).
Click on the image to view the clip again
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CME: initial blast and later impact
This illustrates a CMEs progress from a blast on the
Sun’s surface (lower left) to its impact on the Earth’s
magnetosphere days later (drawing not to scale)
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Earth’s Magnetosphere and a CME
Normal shape
Changed by CME
Electrically charged particles from a CME both compress and lengthen
Earth’s magnetosphere. The particles are guided by Earth’s magnetic field
lines into the polar regions.
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CME impact on Earth’s magnetosphere
Seen on Earth as
aurora, the impact of
a CME on Earth’s
magnetic field is
captured in an
ultraviolet video from
the perspective of a
spacecraft. The red
areas indicate the
most intense
magnetic activity.
Click on the image to play the video
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Some effects of CMEs on Earth
When CME’s interact
with our magnetosphere, strong
magnetic changes
occur, impacting a
wide range of things.
A CME knocked out
power in Quebec in
1989 and interfered
with communications.
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How do some of these effects occur?
As a result of major
magnetic storm activity:
Intense electric currents flow in
the Earth’s atmosphere induces
currents in pipelines (which act
like electric conductors),
causing increased corrosion of
the pipeline.
When charged particles and radiation
from a CME strike satellites, they can
disrupt electronic equipment and even
cause total failure. The atmosphere
also heats and expands, increasing the
drag on satellites in orbit around the
Earth and changing their orbits.
Irregularities in the ionosphere
(about 40-400 km above Earth)
occur, disrupting radio signals
passing through it to satellites
and back, as well as Earth-toEarth communications.
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How can we prepare for CMEs?
With greater reliance on technology for travel, communications,
transportation, and power generation, we need to find ways to
avoid damage and disruptions from CMEs.
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Further improve space weather predictions
Build stronger satellites and more protected systems
Take operational precautions in response to warnings
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NOTE: there is no human health risk from CMEs.
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The SOHO spacecraft
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Is a joint mission of NASA and the European Space
Agency (ESA) to study the Sun for over 3 years
Has 12 instruments to study the Sun’s interior,
atmosphere,and solar wind
Provided most of the images
and video in this presentation
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SOHO’s orbit
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positioned about 1 million miles towards the Sun
from the Earth
keeps that position as Earth orbits around the Sun
studies the Sun 24 hours a day without interference from
the Earth’s atmosphere
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Sun study spacecraft in orbital positions
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X-ray images of Sun reveal changes
The 12 x-ray images of the Sun's atmosphere, 1991-95 at 90 day
increments, show how the corona changes during the solar cycle. Only
very hot gases can emit x rays; the Sun's atmosphere, at millions of
degrees, is hot enough to emit x rays;
the sun’s surface is
not. As the solar
activity cycle declines,
the Sun's magnetic
field changes from a
complex structure to a
simpler configuration.
This represents
another way to study
the Sun over time.
Taken by Yohkoh, an
orbiting Japanese
sun-study spacecraft.
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The Sun transformed through 3 wavelengths
This video shows three
different views of the
Sun in different
wavelengths of light
captured by another
spacecraft’s
instrument. Layers
are built out from the
Sun’s photosphere
(surface), to the
chromosphere (lower
atmosphere), and
finally the corona
(outer atmosphere).
Click on the image to view the clip
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Ground-based Observatories
Numerous observatories around the world continue to
study and capture different images of the Sun.
National Solar Observatory (Sacramento Peak, NM)
Helium white light
image (Kitt Peak
Observatory, NM)
H-Alpha white light image
(Learmonth, Australia)
Coronameter
image (Mauna Loa
Solar Observatory,
Hawaii)
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SOHO’s Web site
Updated daily, the
SOHO Web pages
offer images,
movies,
information,
exercises, links,
and even a place to
ask questions
about the Sun.
http://sohowww.nascom.nasa.gov
Click on Teachers,
and try out our
educational
section!
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Many related Web sites can be explored
Windows to the Universe
http://www.windows.umich.edu/
• engaging Web-site that spans the Earth and Space sciences. Offers
classroom activities and resources.
NASA’s Education Program
http://www.hq.nasa.gov/education/
• introduces educators to NASA’s extensive resources available
NASA’s Space Image Libraries
http://www.okstate.edu/aesp/image.html
• a variety of sources for NASA’s space-related images
Views of the Solar System
http://www.hawastsoc.org/solar/homepage.htm
• an educational tour of the solar system, with images and information
about the Sun, planets, moons, asteroids, comets and meteoroids
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New Views of the Sun poster
Available for
educators from
NASA for free
(lots of
information
and images on
the back, too).
(See the
accompanying
handout for details)
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. . . learning more about the Sun’s
processes and how it affects
the Earth
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Stay tuned for more SUN developments
Remember, it is dangerous to look right at the Sun, so DO NOT.
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