Welcome!
Sun and
Seasons
Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html
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 http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html
The Sun
• Is a star
• Made of gases
70% hydrogen and 28% helium
• Is our primary
source of energy
Light (radiation)
Image at
http://science.nasa.gov/headlines/y2007/images/chromosphere/LimbFlareJan12_strip2.jpg
How Big is the Sun?
Activity: Let’s measure the Sun
How Big is the Sun?
About 110 times
wider than Earth
Or
1.3 million times
bigger than
Earth
Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html
How does our Sun compare to other Stars?
• Active stars range in
size from supergiants to
dwarfs
• 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
mass
Our Sun is a medium-bright
dwarf
Our Sun is in-between--yellow
So is our Sun an average star?
• No—most stars are smaller and cooler than our Sun
BUT
• Most of the bright stars we see are bigger and hotter
Rotation
High cadence solar rotation, EIT 195Š(Dec. 10-24, 1999) Movie at
http://sohowww.nascom.nasa.gov/bestofsoho/Movies/EITdec99/EITdec99sm.mpg
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
http://sohowww.nascom.nasa.gov/bestofsoho/Movies/dynamo/dynamos
m.mpg
Inside the Sun
• Core
• Radiative Zone
• Convection zone
Image at http://solarscience.msfc.nasa.gov/interior.shtml
The Sun’s Atmosphere
• Photosphere
• Chromosphere
• Corona
Photosphere image: http://science.msfc.nasa.gov/ssl/pad/solar/surface.htm
Chromosphere image: http://science.msfc.nasa.gov/ssl/pad/solar/chromos.htm
Corona image: http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=191
Energy from the Sun
•
Nuclear chain reaction (hydrogen forming
helium)
•
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 http://solarscience.msfc.nasa.gov/interior.shtml
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 http://sohowww.nascom.nasa.gov/gallery/top10/top10_results.html
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
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/q
uestion17.html and
http://solarscience.msfc.nasa.gov/SunspotCycle.shtml
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,
2004)
http://sohowww.nascom.nasa.gov/bestofsoho/Movies/171
/EIT171sm.mpg
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 http://solarscience.msfc.nasa.gov/the_key.shtml
Auroras
• 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
http://sohowww.nascom.nasa.gov/bestofsoho/Movies/ani
mation/Solarwind.mpg
Coronal Mass Ejection
This series of images of coronal mass ejections taken with
LASCO C3 (May 1-31, 1997) at
http://sohowww.nascom.nasa.gov/bestofsoho/Movies/C3May97
/C3May97sm.mpg
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.
http://sohowww.nascom.nasa.gov/bestofsoh
o/Movies/recon/reconsm.mpg
Activities
• Let’s go observe the Sun
• Sunspot graphing
Influences on Earth
• Gravity
• Light (Radiation)
• Solar Wind (already discussed)
Gravity
• Orbits
– The Sun’s powerful gravity keeps
the planets in orbit
Radiation
• 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
http://imagine.gsfc.nasa.gov/docs/teachers/gammaraybursts/imagine/page18.html and
http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/sun.html
Activities on Sunlight
• UV Man (or woman, or dog, bug, etc.)
• Observations of infrared light using filters and cell
phones
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
infrared
Electromagnetic spectrum
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/what_is_ir.html
.
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 http://visibleearth.nasa.gov/view_rec.php?id=107
Credit: NASA GSFC Water and Energy Cycle
http://www.nasa.gov/centers/jpl/news/grace-20061212.html
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 http://nasadaacs.eos.nasa.gov/articles/2005/2005_rainforest.html and
http://planetquest.jpl.nasa.gov/TPF/tpf_book/gallery/4-2a.html
Young
stars form
in nebulae
from Small
Magellanic Cloud
Image at
http://hubblesite.org/newscenter/archive/releases/2007/04/image/a/results/50/
Star-forming region in the Large Magellanic Cloud:
http://hubblesite.org/newscenter/archive/releases/2008/31/image/a/results/50/
Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
Our Sun is a Regular/ Small Star
Image at http://www.gsfc.nasa.gov/topstory/20011210insidesun.html
In a few Billion years… Red Giant
Image at http://hubblesite.org/newscenter/archive/releases/1997/26/image/a/
Our Sun’s Habitable Zone
Billions of years ago, things may
have been different
– The Sun was cooler (by up to
30%!)
– Earth’s atmosphere was
different (thicker, carbon
dioxide)
•
Animation at
http://www.nasa.gov/97994mai
n_BHabitableZone.MPG
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 http://hubblesite.org/newscenter/archive/releases/nebula/planetary/1998/39/results/50/
Image at
http://hubblesite.org/newscenter/archive/releases/nebula/planetary/2000/28/image/a/format/web_print/results/50/
Image at http://hubblesite.org/newscenter/archive/releases/nebula/planetary/2004/27/image/a/format/large_web/results/50/
Massive
Stars are
different
Image from
http://hubblesite.org/newscenter/archive/releases/nebula/emission/1997/33/results/50/
Betelgeuse
Image from http://hubblesite.org/newscenter/archive/releases/star/massive%20star/1996/04/image/a/results/50/
Supernova—Massive Star Explodes
Images at
http://hubblesite.org/newscenter/archive/releases/star/supernova/2004/09/results/50/
http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/
http://chandra.harvard.edu/photo/2009/casa/
Done with the Sun
• Time for Seasons!