Montgomer y Productio ns Proudly Present: The Sun
Mar 27, 2015
Montgomery
Productions
Proudly Present:
The Sun
The Sun
• Is a star
• Made of gases
– 71% hydrogen
– 27% helium
• Is our primary source of energy
– Light (radiation)
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
The Sun and its Planets to Scale
• The Sun contains about 99.8% of the total mass of the Solar System.
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
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
The Sun’s Energy
• Fusion – combination of lightweight atomic nuclei into heavier nuclei.– i.e. hydrogen fusing
into helium– E=mc2
• Fission – splitting of heavy atomic nuclei into lighter nuclei
Radiation• Our Sun (and all active stars) emits radiation
– Radio, infrared, visible, ultraviolet, x-ray and even some gamma rays
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’s Radiation at Earth
• The Earth’s 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.caltech.edu/cosmic_classroom/ir_tutorial/what_is_ir.html
.
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, it is transformed into heat energy.
Like a hot sidewalk…
Sun as a Source of Energy• Light from the Sun is absorbed by the Earth to:
– drive photosynthesis– 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
Anticipated Future of the Sun
Birth: Gravitational Collapse of Interstellar Cloud Formation of Protostar
Life: Stability on Main-Sequence Long life - energy from nuclear reactions in the core(E = mc2)
Death:Lack of fuel, instability, variability expansion (red giant, then white dwarf)
Life Cycle of the Sun
Until then, make sure you wear sunscreen