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The Sun
Why?
28
Astronomy
Undergraduate 1
11/20/2008

Additional Astronomy Flashcards

 


 

Cards

Term
Photosphere
Definition

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

 

 

 

Term
Limb Darkening
Definition

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

 

 

Term
Granules
Definition

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) 

 
Term
Chromosphere
Definition

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

 

scientists can also see it by using filters or through telescopes
 
sensitive to the wavelengths the chromospheres emits

 

 

Term
Spicules
Definition

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 

Term

Supergranules

Definition

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 


Term
Corona
Definition

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

Term
Transition Zone
Definition
Area between the chromosphere and corona where temperatures skyrocket to 1 million K
Term
Solar Wind
Definition

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

Term
Sun Spots
Definition

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

 

 

 

Term
Sun Spot maximum
Definition

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

 

Last solar maximum : 2001

Next solar maximum : 2012

Term
Sun Spot Minimum
Definition
The time during the solar cycle when the number of sunspots is minimum
Term
Umbra (with sunspots)
Definition
dark, central region of the sunspot
Term
Penumbra (with sunspot)
Definition
Brighter ring surrounding umbra on a sunspot
Term
Zeeman Effect
Definition

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 

 

Term
Plasma
Definition

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

 

Below the photosphere, gasses around sunspots are whipping around like a hurricane. This circulation of charged gasses around the magnetic field keeps it in place

 

Term
Solar Flares
Definition

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.

Term
Mass of the Sun
Definition
330,000 x bigger than the mass of the Earth
Term
Radius and Density
Definition

Radius: 109 x that of Earths

Density: 1400 kg/m^3 (cubed)

Term
How Sun spins...
Definition

Spins differentially

p= 25 days at equator

p= 36 days at poles

Term
What is the closest star to Earth?
Definition
The sun is the closest star to Earth
Term
Magnetic Field (strong, weak?)
Definition
The sun has an extremely powerful magnetic field that is discussed throughout other terms (such as sunspots etc.)
Term
Composition of the Sun & How do we know?
Definition

75 % Hydrogen

24% Helium

1% trace elemtns

 

How do we know? 

Spectrocopic measurement 

Analysis of the solar winds 

Term
Prominences
Definition

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

 

Term
Formation of Sun Spots
Definition

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 

 

 

 

 

Term
Energy of the Sun
Definition

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

  • high gravitational pressure
  • high temperaturesE
Term

Structure of the Sun

-Solar Core

-Radiative Zone

-Convenctive Zone

Definition

Solar Core

  • Nuclear fusion produces energy

RadiativeZone
  • Energy is transported by photons of light

Convective Zone
  • Warmer gas moves upward, cool gas sinks
Term
Hydrostatic Equilibrium
Definition

Balance between outward thermal pressure and inward pull of gravity

 

Maintains Sun at a relatively constant size

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