visible layer of the sun, visible light comes from this one specific gas layer; region in the solar atmosphere from which most of the visible light escapes into space

3rd layer of the sun

temperature about 5800 K

low density (compared to Earth)

Layers under photosphere considered sun’s interior

Due to the photospheres high temperature, many atoms in it are ionized (one or more electrons have been stripped off by high energy photons there)—mix of electrically charged ions and electrons called plasma

photosphere appears darkest toward the edge (or limb) of the sun; phenomenon whereby the sun is darker near its limb than near the center of its disk

occurs because we look through the same amount of solar atmosphere at all places 

since sun is spherical, the light seen leaving the sun at different places comes from different levels of the photosphere 

from Earth, when we look at the center of the sun, we see further into the Sun’s atmosphere than when we look at its limbs, giving it a hotter, yellower appearance and giving the limbs a darker, cooler, orange color

Lightly colored convection features about 1000 km in diameter seen constantly in the solar photosphere

surrounded by relatively dark boundaries

Time lapse photography shows them disappearing every several minutes, and new ones forming

From the granules gas escapes; hot gasses move upward, and the cooler gasses roll back off the granules, creating the dark surrounding boundaries (convection) 

layer above the photosphere (visible layer of sun); layer in the solar atmosphere between the photosphere and the corona (1st layer/most outer layer of sun)

called “sphere of color” but is almost always transparent to us

can see it during an eclipse as a pinkish strip around the edge of the dark moon

Spikes found on the chromosphere which are jets of gas; a narrow jet of rising gas in the solar chromosphere

spicule rises for several minutes rapidly to a height of about 10,000km before collapsing 

millions of them covering chromosphere 

Supergranules

Boundaries of enormous regions of rising and falling chromosphereic gas where spicules are generally located; a large convective cell in the Sun's chromosphere containing many granules

one is roughly the size of Earth and contains 900 granules 

Outermost region of the sun

Discovered Coronas strangely high temperature by examining spectral lines which contained a number of highly ionized elements (the hotter a gas is, the more ionized it is)

  Extremely thin density which explains why it is not visible to us, otherwise it would greatly outshine photosphere

There is evidence that the corona is heated by energy carried aloft and released by the sun’s complex magnetic fields 

Can be seen during a solar eclipse

An outward flow of particles (mostly electrons and protons) from the Sun

Some gas in corona is moving fast enough to escape sun’s gravity, creating this force 

This outflow of gasses prevents most of the gases flowing in space (from other stars) from entering our solar system

Though a million tons of matter is being ejected every second, very little mass will be lost from the solar wind

A temporary cool region in the solar photosphere created by protruding magnetic field

sometimes occur in isolation, but usually in groups called sunspot groups

 Average sunspot cycle is 11 years

Sunspots last from a few hours to a few months

Two parts to sunspots, umbra, and penumbra

 Last approximately 2 rotations of the sun

The time during the solar cycle when the number of sunspots is greatest

Last solar maximum : 2001

Next solar maximum : 2012

the "splitting" of a single spectral line into two or more lines

Intense magnetic field splits the spectral lines of a light source inside the field

The more intense the field, the more the split lines are separated 

Mix of electrically charged electrons and ions

Plasmas are extremely good conductors of electricity and are repelled from regions of high magnetic field

Where magnetic field protrudes through photosphere, it prevents hot, ionized gases inside the sun from rising up as they normally would –hence they are cooler than the other parts and become dark, sunspots

So how are they held in place? Magnets repel—so the sunspots should dissipate faster than a few months

Eruptive events on the sun; a violent eruption on the suns surface

release vast quantities of high-energy particles, X rays and UV radiation 

last for less than an hour, but reach 5 million K 

Interferes with power plants, radios, etc.

Radius: 109 x that of Earths

Density: 1400 kg/m^3 (cubed)

Spins differentially

p= 25 days at equator

p= 36 days at poles

75 % Hydrogen

24% Helium

1% trace elemtns

How do we know? 

Spectrocopic measurement 

Analysis of the solar winds 

Hot gas expelled by the sun and caught by its magnetic field (arched apperance)

Sun rotates faster at the equator than at the poles (differential rotation)

Magnetic field under sun gets wound up

Magnetic field gets pushed under surface

Magnetic field inhibits warmer gas from moving to those areas where field pushes through surface 

Sun produces energy through the process of nuclear fusion

4 hydrogen atoms are combined to form one helium atom

During fusion, some of the mass is transferred into energy according to Einstein’s famous equation…

E=mc^2 (squared) E=energy

                           m=mass

                          c= speed of light

Fusion can occur in the core of the Sun

Structure of the Sun

-Solar Core

-Radiative Zone

-Convenctive Zone

Solar Core

Balance between outward thermal pressure and inward pull of gravity

Maintains Sun at a relatively constant size