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The Sun. Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html. 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/images/chromosphere/LimbFlareJan12_strip2.jpg. - PowerPoint PPT Presentation
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The Sun
Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html
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/images/chromosphere/LimbFlareJan12_strip2.jpg
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 in-between--yellow
Our Sun is a dwarf—medium mass
Our Sun is a medium-bright dwarf
Rotation
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”
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
Inside the Sun
• Core
• Radiative Zone
• Convection zone
Image at http://solarscience.msfc.nasa.gov/interior.shtml
The Sun’s Atmosphere
• Photosphere
• Chromosphere
• CoronaPhotosphere 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
The Photosphere
• Photosphere: The ‘Surface’ of the Sun, and the layer from which light is given off
• Sunspots: areas of the sun that look dark due to being cooler
Chromosphere & Corona
• Chromosphere: middle layer of the Sun’s atmosphere
• Corona: Largest layer of the Sun’s atmosphere
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
Coronal Mass EjectionCMEs: large amount of electrically-charged gas are ejected suddenly from the Sun’s corona
CMEs can damage satellites and interfere with radio and power distribution equipment
Prominences and Flares• Prominences- huge arching columns of gas• Flares: when gases near a sunspot brighten
shooting outward
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
.
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
Our Sun is a Regular/ Small Star
Image at http://www.gsfc.nasa.gov/topstory/20011210insidesun.html
Stars begin as a cloud of gas
and dust called
nebula
Image at http://hubblesite.org/newscenter/archive/releases/2007/04/image/a/results/50/
Main Sequence
Image at http://hubblesite.org/newscenter/archive/releases/1997/26/image/a/
Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star
• After billions of years a Main sequence star will turn into a Red Giant
By 5 billion years… White Dwarf:This happens when all that is left is the hot
dense core
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/
Supergiant's and SupernovasSupergiant's: Extremely large (and unstable red giants
Supernovas: The explosion that occurs when the supergiant’s core collapses
Black Hole• If the remaining dense core from a supernova
collapses to a point• The gravity from this point is so strong that
nothing can escape from it not even light.– If you were to shine a light into a black hole
the light would simply disappear
Life of a Star