From the Core to the Corona – a Journey through the Sun

A Model for most stars in the A Model for most stars in the UniverseUniverse

The Sun’s Core The Sun’s Core

The energy production The energy production sitesite

Temperature = about 15 million degrees Temperature = about 15 million degrees KelvinKelvin

Energy is generated in the core by Energy is generated in the core by nuclear fusionnuclear fusion

Nuclear fusion is due to great pressures Nuclear fusion is due to great pressures causing protons from hydrogen to slam causing protons from hydrogen to slam into one another creating heliuminto one another creating helium

The core accounts for 40% of the sun’s mass, while only occupying 10% of the total volume.

In other words, the core is really really really dense…

The Radiation The Radiation ZoneZone

Upward and Outward!Upward and Outward! Energy is transported out Energy is transported out

of the core of the Sunof the core of the Sun Much less dense than coreMuch less dense than core Energy has a harder time Energy has a harder time

passing through it. passing through it. Energy is free movingEnergy is free moving

It can take hundreds of It can take hundreds of thousands to millions of thousands to millions of years of years for energy years of years for energy (light) to get out of the (light) to get out of the radiation zoneradiation zone

The Radiation ZoneThe Radiation Zone Towards the edge of the radiation zone, Towards the edge of the radiation zone,

the temperature cools enough that the the temperature cools enough that the energy from the core cannot move freely. energy from the core cannot move freely.

Instead it gets absorbed by the plasma Instead it gets absorbed by the plasma (hot gas of the Sun) and starts a process (hot gas of the Sun) and starts a process known as convection.known as convection.

Convection ZoneConvection Zone• The outermost layer of the

Sun’s interior layers• Brings light and energy to the

surface of the Sun through convection currents

• Temperature range from 2 million to 6,000 degrees Kelvin.

The PhotosphereThe Photosphere

The lower The lower atmosphere of the atmosphere of the SunSun

This is where the This is where the energy finally is energy finally is released, mostly as released, mostly as thermal energy, but thermal energy, but also as the visible also as the visible light we see.light we see.

The coolest region of The coolest region of the Sun (6000 the Sun (6000 Kelvin)Kelvin)

GranulationGranulation The Sun’s photosphere The Sun’s photosphere

looks like rice grains. looks like rice grains. Large convection cells Large convection cells

cause this granulation, cause this granulation, since each cell has a since each cell has a column of hot gas rising column of hot gas rising and cool gas and cool gas descending. descending.

Granules the size of Granules the size of Earth and larger Earth and larger constantly evolve and constantly evolve and change in a churning change in a churning kind of motion.kind of motion.

ChromosphChromosphereere

The region immediately The region immediately above the photosphere above the photosphere

2000-3000 km thick2000-3000 km thick Glows faintly relative to Glows faintly relative to

the photospherethe photosphere Can only be seen easily Can only be seen easily

in a total solar eclipsein a total solar eclipse Temperature is about Temperature is about

20,000 degrees Kelvin20,000 degrees Kelvin Primary source of UV Primary source of UV

radiationradiation

The Solar The Solar CoronaCorona

The corona is extended outer atmosphere of the Sun

1 million times less bright than the photosphere

Can only be seen during a total solar eclipse or by using a tool called a coronagraph, which artificially blocks out the disk of the Sun.

6,000 K

1,000,000 K

The Sun’s surface temperature is about 6,000 degrees K

The temperature in the corona reaches about 1 million degrees K

The Solar WindThe Solar Wind A constant stream of particles flows from the Sun’s corona, with a temperature of about a A constant stream of particles flows from the Sun’s corona, with a temperature of about a

million degrees and with a velocity of aboutmillion degrees and with a velocity of about 450 kilometers per second 450 kilometers per second. . The solar wind reaches out beyond Pluto's orbit (about The solar wind reaches out beyond Pluto's orbit (about 5900 million kilometers)5900 million kilometers). . This wind helpsThis wind helpsshape the magneto-shape the magneto-spheres of planetsspheres of planetsand blows off theand blows off thematerial that formsmaterial that formsthe tails of comets.the tails of comets.

The Path of SunspotsThe Path of Sunspots Because of Because of differential rotation, differential rotation, the magnetic the magnetic

field of the Sun is very much different from that field of the Sun is very much different from that of the Earth.of the Earth.

Sunspots often occur in pairs along these lines.Sunspots often occur in pairs along these lines.

The Path of SunspotsThe Path of Sunspots

Strong magnetic forces prevent the Strong magnetic forces prevent the mixing of cooler and warmer areas, which mixing of cooler and warmer areas, which creates the appearance of sunspots.creates the appearance of sunspots.

This is also the path for solar prominencesThis is also the path for solar prominences

The Path of SunspotsThe Path of Sunspots

Notice how the Notice how the prominence seems prominence seems to loop similar to to loop similar to the magnetic fieldthe magnetic field

The Path of SunspotsThe Path of Sunspots

Sunspot Cycle – sunspot maximum occurs every 11 years. Last sunspot maximum was in 2001.

Solar Solar ProminencesProminences A fairly common occurrenceA fairly common occurrence They are eruptions caused by magnetic forces. They are eruptions caused by magnetic forces.

Cooler gases above the photosphere can often Cooler gases above the photosphere can often be seen flowing along magnetic field lines.be seen flowing along magnetic field lines.

Large Solar Large Solar Prominences Prominences

• This is the largest prominence observed.

• This huge prominence is 100,000 kilometers above the Sun.

28 Earths high

Some Neat Little Some Neat Little Ditties.Ditties.

How do we know the temperature of the Sun?How do we know the temperature of the Sun? Wiens’s Law = Hotter bodies radiate more energy at shorter wavelengths.Wiens’s Law = Hotter bodies radiate more energy at shorter wavelengths.

Each wavelength has its own colorEach wavelength has its own color So, temperature is related to surface color of the star and hotter stars are brighter if seen from the So, temperature is related to surface color of the star and hotter stars are brighter if seen from the

same distancesame distance

How do scientists know that the Sun has a core?How do scientists know that the Sun has a core? The only thing that provides enough energy to heat a star for billions of years is nuclear fusion. The only thing that provides enough energy to heat a star for billions of years is nuclear fusion.

How long until the Sun explodes?How long until the Sun explodes? About 5,000,000,000 years.About 5,000,000,000 years.

How do we know the composition of the Sun?How do we know the composition of the Sun? The solar wind and spectra analysis.The solar wind and spectra analysis.

Sunspot CycleSunspot Cycle sunspot maximum occurs every 11 years. Last sunspot maximum was in 2001.sunspot maximum occurs every 11 years. Last sunspot maximum was in 2001.

One second of its Energy = total energy produced in the US for 90 yearsOne second of its Energy = total energy produced in the US for 90 years

Is one of about 2 billion medium sized stars in out galaxyIs one of about 2 billion medium sized stars in out galaxy

If you drove a car at 100 miles per hour to the Sun, how many years would it take If you drove a car at 100 miles per hour to the Sun, how many years would it take to get there? 5, 50 or 100.to get there? 5, 50 or 100.

About 100 yearsAbout 100 years