The Sun

The Sun

The Sun• Is a star• Made of gases• Is our primary

source of energy

• Contains 99.8% of the entire mass of Solar System

70% hydrogen and 28% heliumLight (radiation)

Image at http://science.nasa.gov/headlines/y2007/images/chromosphere/LimbFlareJan12_strip2.jpg

How Big is the Sun?About 110 times wider than EarthOr1.3 million times bigger than Earth

865 thousand miles wide

Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html

Interesting Facts about the sun

• Light takes 8 minutes to reach the Earth

(5.3 hours to reach Pluto)

• Sun emits radio waves – listen to the sun…from NASA SOHO satellite

http://www.youtube.com/watch?v=GWCJkG31h0c

The Sun and its Planets to Scale

Inside the Sun• Core• Core• Radiative Zone• Convection zone

Image at http://solarscience.msfc.nasa.gov/interior.shtml

How does the sun produce energy?

• The Sun produces energy by the nuclear fusion of hydrogen into helium in its core.

Nuclear Fusion• hydrogen atoms in the core are

crushed together (fused) into a helium atom and energy

• energy is then radiated out from the core and moves across the solar system

Hydrogen yields Helium + ENERGY

Great Pressure

Sun’s Atmosphere Layers

The Sun’s Atmosphere Layers

Photosphere Chromosphere CoronaSurface of sun Above

PhotosphereOuter atmosphere of sun

where light is emitted

H at this temp gives sun its color

Produces solar wind

Temp 6,000° C Temp 20,000° C Temp 2 million° C

Features of the Sun

Sun Spots• Sun Spots- These are dark, cool areas on

the photosphere• come in pairs • intense magnetic fields reduce energy in that

spot• Caused by movement of gases tangling

the magnetic field

Solar Flares• Solar Flares are sudden,

violent explosions from the sun

• release gas, electrons, visible light, ultraviolet light and X-rays

• caused by sudden magnetic field changes in areas where the sun's magnetic field is concentrated (often near sun spots)

Effects of Solar Flares• When charged particles reach the Earth's

magnetic field, they interact with it at the poles to produce the auroras

• Solar flares can disrupt communications, satellites, GPS navigation systems and even power grids

Coronal Mass Ejections (CME’s)

• Solar flares twist back on themselves and cut off from the sun

• Release blob of plasma into space• Plasma is superheated electrically

charged gas

Effects of CME• Can damage satellites and

communications

• Very dangerous to astronauts

• Power interruptions

Solar Wind• Blows charged particles away from

the Sun• Charged particles hit Earth’s

magnetic field• Create Auroras or Northern

(borealis) and Southern (australis) Lights

http://sohowww.nascom.nasa.gov/bestofsoho/Movies/animation/Solarwind.mpg

Auroras• Solar wind charged particles interact

with atoms in our atmosphere near poles

• oxygen and nitrogen make red and green

• nitrogen can also make violet

How does the sun affect the Earth?• Gravity

- Orbits- The Sun’s powerful gravity keeps the planets in orbit

- Location - Our distance from the Sun is “just right” for temperature and brightness of the Earth

• 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 visible light. • Solar Phenomena- Solar flares, CME’s• Earth’s protection - Earth’s atmosphere filters out some frequencies- Ozone layer protects us from some ultra-violet, and

most x-rays and gamma rayso Warmth

The Sun keeps us warm…• Sunlight is absorbed by Earth• The Sun does NOT send “heat rays”

into space. • The Sun’s light is absorbed by Earth

(clouds, plants, oceans, rock…)• Absorbed light energy is re-emitted as

infra-red – The Greenhouse Effect • Earth’s atmosphere is warmed by the

Earth’s surface

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 massOur 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