The SunThe Sun

Unit 5Unit 5

PESS 2PESS 2

Energy from the SunEnergy from the Sun

• Electromagnetic energy is a type of energy that can travel through space an example is visible light

• Light travels in wavelengthsLight travels in wavelengths– There are many things that There are many things that

travel in wavelengths (radio travel in wavelengths (radio waves, microwaves, waves, microwaves, ultraviolet rays, x-rays)ultraviolet rays, x-rays)

• The electromagnetic spectrum breaks visible light down into the colors that make it up– When you shine light through When you shine light through

a prism you can see the a prism you can see the different colors of visible light different colors of visible light

Electromagnetic Radiation Electromagnetic Radiation

• Visible light is Visible light is composed of red, composed of red, orange, yellow, orange, yellow, green, blue and green, blue and violet – like a violet – like a rainbowrainbow

Energy from the SunEnergy from the Sun

• In a process called nuclear fusion the sun gives off electromagnetic energy

• Nuclear fusion can only occur Nuclear fusion can only occur at extremely high at extremely high temperatures (temperatures (~15 million °C)~15 million °C)– Helium and hydrogen atoms Helium and hydrogen atoms

fuse together giving off an fuse together giving off an enormous amount of energy enormous amount of energy (enough to supply the solar (enough to supply the solar system for billions of years!)system for billions of years!)

• There is enough helium and There is enough helium and hydrogen in the sun to last hydrogen in the sun to last about 10 billion years – the about 10 billion years – the sun is only about 5 billion sun is only about 5 billion years oldyears old

Measuring our Solar SystemMeasuring our Solar System

• Since the solar Since the solar system is so large system is so large scientists developed scientists developed the unit called an the unit called an astronomical unit or au

• The distance between the sun and Earth is 1au

The Sun’s InteriorThe Sun’s Interior

• Consists of: Core, Radiation zone, Convection zone

• Core– Where nuclear fusion occursWhere nuclear fusion occurs– About 400,000kmAbout 400,000km

• Radiation zoneRadiation zone– Region of highly compressed Region of highly compressed

gasesgases– Takes energy “light” about Takes energy “light” about

10,000 years to pass through10,000 years to pass through

• Convection zoneConvection zone– Convection currents move the Convection currents move the

energy to the atmosphereenergy to the atmosphere

The Sun’s Atmosphere The Sun’s Atmosphere

• There are 3 layers – the photosphere, the chromosphere and the corona

• The Photosphere– The inner layerThe inner layer– Technically, the “surface”Technically, the “surface”– About 5800K and 500km thickAbout 5800K and 500km thick

• The Chromosphere– The middle layerThe middle layer– Gives off a reddish glowGives off a reddish glow– About 10,000KAbout 10,000K– Visible during a total solar Visible during a total solar

eclipseeclipse

The Sun’s AtmosphereThe Sun’s Atmosphere

• The Corona– The white halo around the The white halo around the

sunsun– Visible on Earth only during Visible on Earth only during

eclipses or by special eclipses or by special telescopestelescopes

– Sends out a stream of Sends out a stream of electrically charged electrically charged particles called solar windparticles called solar wind

– The Earth’s atmosphere The Earth’s atmosphere normally blocks out solar normally blocks out solar wind, but near the north wind, but near the north and south poles some and south poles some particles enter creating particles enter creating auroras auroras

– About 1 million KAbout 1 million K

Features of the SunFeatures of the Sun

• The sun rotates on its The sun rotates on its axis, just like all the axis, just like all the other planets in the other planets in the solar systemsolar system

• SunspotsSunspots– Small, dark spots on the Small, dark spots on the

sun sun (small for the sun (small for the sun because they are about the because they are about the size of Earth)size of Earth)

– Sunspots are areas of gas Sunspots are areas of gas that are cooler than the that are cooler than the gases around it – since they gases around it – since they are cooler they do no give are cooler they do no give off as much light and off as much light and appear darkappear dark

Features of the SunFeatures of the Sun

• Scientists believe that the Scientists believe that the number of sunspots change number of sunspots change over 10 years or so – over 10 years or so – meaning that the amount of meaning that the amount of energy produced by the sun energy produced by the sun also changesalso changes

• ProminencesProminences– A group of sunspots that link A group of sunspots that link

together and create reddish together and create reddish loopsloops

– If a prominence is near the If a prominence is near the edge of the sun scientists edge of the sun scientists can actually see them stick can actually see them stick out from the sun’s surface out from the sun’s surface

Features of the SunFeatures of the Sun

• Solar flares– When sunspots suddenly

connect and release a large amount of energy into space

– The gases contract an heat to The gases contract an heat to even greater temperatures even greater temperatures causing hydrogen gas to causing hydrogen gas to explode into spaceexplode into space

– Solar flares can cause Solar flares can cause magnetic storms in the upper magnetic storms in the upper atmosphere of Earth atmosphere of Earth disrupting radios, telephones, disrupting radios, telephones, television, and causing television, and causing electrical problemselectrical problems