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