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.htmlhttp://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 dwarfmedium mass Our Sun is a medium-bright dwarf
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
The Suns Energy Fusion – combination of lightweight atomic nuclei into heavier nuclei. –i.e. hydrogen fusing into helium –E=mc 2 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.htm l and http://imagine.gsfc.nasa.gov/docs/teachers/gammaraybursts/imagine/page18.htm l http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/sun.html.
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.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 Suns light is absorbed by Earth (clouds, plants, oceans, rock…) By absorbing the light, it is transformed into heat energy.
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 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
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