Sun and Seasons

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Welcome!
Sun and Seasons
Photo from http//sohowww.nascom.nasa.gov/bestofso
ho/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.
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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/bestofso
ho/bestofsoho.html
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The Sun

• Is a star
• Made of gases
• Is our primary source of energy

70 hydrogen and 28 helium
Light (radiation)
Image at http//science.nasa.gov/headlines/y2007/i
mages/chromosphere/LimbFlareJan12_strip2.jpg
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How Big is the Sun?
Activity Lets measure the Sun
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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/bestofso
ho/bestofsoho.html
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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 dwarfmedium mass
Our Sun is a medium-bright dwarf
Our Sun is in-between--yellow
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So is our Sun an average star?

• Nomost stars are smaller and cooler than our Sun
  BUT
• Most of the bright stars we see are bigger and
  hotter

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Rotation
High cadence solar rotation, EIT 195Š(Dec. 10-24,
1999) Movie at http//sohowww.nascom.nasa.gov/best
ofsoho/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
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Suns 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/dynamosm.mpg
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Inside the Sun

• Core
• Radiative Zone
• Convection zone

Image at http//solarscience.msfc.nasa.gov/interio
r.shtml
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The Suns Atmosphere

• Photosphere
• Chromosphere
• Corona

Photosphere image http//science.msfc.nasa.gov/s
sl/pad/solar/surface.htm Chromosphere image
http//science.msfc.nasa.gov/ssl/pad/solar/chromos
.htm Corona image http//solarsystem.nasa.gov/mu
ltimedia/display.cfm?IM_ID191
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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/interio
r.shtml
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Features in the Photosphere

• Sunspots
• Dark and small (but brighter than Full Moon
  and big as Earth)
• Cool-- temperatures only 6,200 F (Suns 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/to
p10/top10_results.html
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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/Star
Child/questions/question17.html and
http//solarscience.msfc.nasa.gov/SunspotCycle.sht
ml
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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/besto
fsoho/Movies/171/EIT171sm.mpg
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Solar Wind

• Blows charged particles and magnetic fields away
  from the Sun
• Charged particles captured by Earths magnetic
  field
• Create Auroras or Northern and Southern Lights

Image at http//solarscience.msfc.nasa.gov/the_key
.shtml
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Auroras

• Electrons from solar wind are captured by the
  Earths 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/a
nimation/Solarwind.mpg
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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/C
3May97/C3May97sm.mpg

• The eruption of a huge bubble of hot gas from the
  Sun

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CMEs 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
/bestofsoho/Movies/recon/reconsm.mpg
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Activities

• Lets go observe the Sun
• Sunspot graphing

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Influences on Earth

• Gravity
• Light (Radiation)
• Solar Wind (already discussed)

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Gravity

• Orbits
• The Suns powerful gravity keeps the planets in
  orbit

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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/doc
s/teachers/gammaraybursts/imagine/page18.html
and http//starchild.gsfc.nasa.gov/docs/StarChild/
solar_system_level2/sun.html .
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Activities on Sunlight

• UV Man (or woman, or dog, bug, etc.)
• Observations of infrared light using filters and
  cell phones

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Suns Radiation at Earth

• The Earths atmosphere filters out some
  frequencies
• Ozone layer protects us from some ultra-violet,
  and most x-rays and gamma rays
• Water and oxygen absorb some radio waves
• Water vapor, carbon dioxide, and ozone absorbs
  some infrared

Electromagnetic spectrum http//coolcosmos.ipac.c
altech.edu/cosmic_classroom/ir_tutorial/what_is_ir
.html .
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Sunlight is absorbed by Earth

• Lets test what happens to the light.
• Activity Time!!

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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 Suns light is absorbed by Earth (clouds,
  plants, oceans, rock)
• By absorbing the light, we are transforming it
  into heat energy

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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

Credit NASA GSFC Water and Energy Cycle
http//www.nasa.gov/centers/jpl/news/grace-200612
12.html
NASA image at http//visibleearth.nasa.gov/view_re
c.php?id107
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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
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Young stars form in nebulaefrom Small
Magellanic Cloud
Image at http//hubblesite.org/newscenter/archive/
releases/2007/04/image/a/results/50/
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Star-forming region in the Large Magellanic
Cloud http//hubblesite.org/newscenter/archive/re
leases/2008/31/image/a/results/50/
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Orion image at http//hubblesite.org/newscenter/ar
chive/releases/2006/01/image/a/results/50/
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Our Sun is a Regular/ Small Star
Image at http//www.gsfc.nasa.gov/topstory/2001121
0insidesun.html
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In a few Billion years Red Giant
Image at http//hubblesite.org/newscenter/archive/
releases/1997/26/image/a/
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Our Suns Habitable Zone

• Billions of years ago, things may have been
  different
• The Sun was cooler (by up to 30!)
• Earths atmosphere was different (thicker, carbon
  dioxide)
• Conditions will be different in the future
• By many accounts, increases in the Suns
  temperature will make Earth uninhabitable in 1
  billion years or less
• These changes will also affect other planets
  Mars?

Animation at http//www.nasa.gov/97994main_BHabita
bleZone.MPG
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By 5 billion years White Dwarf
Image at http//hubblesite.org/newscenter/archive/
releases/nebula/planetary/1998/39/results/50/
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Image at http//hubblesite.org/newscenter/archive/
releases/nebula/planetary/2000/28/image/a/format/w
eb_print/results/50/
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Image at http//hubblesite.org/newscenter/archive/
releases/nebula/planetary/2004/27/image/a/format/l
arge_web/results/50/
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Massive Stars are different
Image from http//hubblesite.org/newscenter/archiv
e/releases/nebula/emission/1997/33/results/50/
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Betelgeuse
Image from http//hubblesite.org/newscenter/archiv
e/releases/star/massive20star/1996/04/image/a/res
ults/50/
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SupernovaMassive 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/
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Done with the Sun

• Time for Seasons!