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66 Cards in this Set

  • Front
  • Back
The sun is the sole source of
Our sole source of light and heat in the solar system
The sun is a "common star". What is a common star?
a glowing ball of gas held together by its own gravity and powered by nuclear fusion at its center.
What forces balance to keep the spherical shape of the sun?
The pressure of nuclear fusion reactions and the internal attractive force of gravity.
What would happen if nuclear reactions stop?
the sun would collapse because the outward force would stop and the gravitational force will take over.
What are the main regions of the sun? From inside out.
Core, Radiation zone, Convection zone, photosphere, chromosphere, transition zone, corona.

What region of the sun is the largest?
Radiation zone
What is the sun's radius?
696,000 km (100 times Earth)
What is the Sun's mass?
2e30 kg (300,000 times earth)
What is the sun's density relative to Earth?
Less (made of gas)
What is the rotational period of the sun?
Like the Jovian planets the center turns faster than the poles:

Center: 25 days
Poles: 36 days
What is the surface temperature? What is the internal temperature?
6000K ; 15 million K
What is the luminosity of the sun?
light energy emitted by the sun in one second. (4e26 Watts)
How do we know about the center of the sun if we cant even see it?
Helioseismology- the sun's center vibrates like a bell and the vibrations are propogated in the photosphere (this gives us data from the center of the sun).
What is helioseismology?
Obtaining the vibrational patterns that originally occur in the center of the Sun and are propogated by the photosphere. Then the analysis of this data to determine characteristics of the Sun's core.
According to the Standard Solar model, what occurs as we move to the center of the Sun?
the temperature increases (from 6000K to 15 million K) and the DENSITY increases.
What is important about the 15 million temperature in the center of the sun?
This high temperature allows ionization of many elements other than Hydrogen and helium, assuring that the solar system remains lit.
Notice how the outer portion of the Sun’s disk is darker than the central portion.

-What is this called?
-What causes this?
Limb darkening;

The outer edges of the sun are the coolest on the sun and appear darker.
Based on the last card, what should we know about sunspots?
They are among the coolest spots on the surface of the sun.
Energy transport in the sun:

At the core ___________ occurs.
ionization of gases.

This means that no electrons are left on the elements in the core to absorb photons.
Energy transport in the sun:

As a result of all the elements at the core losing their electrons...
the sun is transparent since there are no electrons to absorb photons.
Energy transport in the sun:

Because there is NO absorption of photons, the core is called a...
radiation zone.
Energy transport in the sun:

As we move away from the core, the temperature drops and we find what?
more non-ionized atoms.

Thus some light is absorbed in the convection zone.
Energy transport in the sun:

Because some light is absorbed in the convection zone, light is ______
Energy transport in the sun:

Beyond the convection zone what occurs?
The low density (since we are further from the core) makes the photosphere transparent to light (Another radiation zone).
this process takes over when the gas is too opaque for radiative energy transport.
What causes convection?
the fact that hot air is less dense and rises and that cool air is more dense and sinks.
What is the evidence that convection actually occurs on the sun?
Solar Granulation are the tops of the convection zome. The darker regions indicate cooler air sinking on to the sun and the brighter region indicate warmer air rising.
According to the doppler effect measurement of convection cells how fast does matter rise and sink?
1 km/sec
As a result of spectroscopy studies, how many elements are believed to exist on the Sun? which are the most abundant?
67 elements; Hydrogen followed by helium.
What is one of the major disadvantages of using spectroscopy to learn about the Sun?
Information can only be obtained for the regions of the sun that produce the light (Chromosphere and photosphere).

It is believed that the sun is homogenous enough that the rest of the sun is the same.
Can the chromosphere be seen during an eclipse? what color does it appear? Why?
Yes; Red;

NOT AN INDICATOR OF TEMPERATURE... instead its the light released from electrons going from the 3rd to 2nd energy levels.
What structures are found on the Sun's chromosphere? What are they? What light do they absorb?

warm jets of matter shooting out (volcano-like)

H alpha light
What do astronomers believe causes spicules on the chromosphere?
DISRUPTIONS to magnetic fields.
What is unique about the transition zone and corona?
The temperature is VERY HOT.
why does the temperature increase out here (further from the sun's core)?
Because of magnetic activity (which also causes spicules and more energetic phenomena)
Can the corona be seen during an eclipse?
What is it that is actually being seen when we look at the corona?
escaped hot gas that has been blown away from the surface of the Sun by Solar wind.
Coronal gas has enough heat (kinetic energy) to do what?
Overcome the Sun's gravitational pull. It passes its escape speed and some is carried off by solar wind.
Is the sun evaporating? How much? Is this a concern?
Yes; 1 million tons/sec; no because in its existance the sun has only lost .1% of its mass.
How fast does solar wind travel? How long does solar wind from the sun cause to reach Earth?
500 km/s; 3 days.
What is the source of solar winds? What causes them?
Coronal holes (low-density regions); magnetic field activity.
What causes the Sun's luminosity?
The Sun gives off light in the UV section of the spectrum. MOST of it is a result of photospheric emission. However, a small portion is from an "irregular component" (??)
Sunspots: Why are they dark?
Dark color because they are cooler than photospheric gas (4500K in darkest parts vs. 6000K on the surface.)
What did the history of sun spots contribute to knowlege of the sun's rotation?
Galileo observed these spots and realized the sun is rotating differentially (faster at the equator, slower at the poles
What three lines of evidence suggest that sun spots are caused by magnetic fields?
1.) The magnetic field at sun spots is 1000x greater than on normal solar surface area.

2.) Almost always in pairs

3.) ALways have the same configuration in a given hemisphere.
How does magnetic field cause sun spots?
Where magnetic fields come out of the Sun's photosphere, hot gas is not allowed to convect outward thereby cooling that region of the photosphere causing it to look black.
What causes the sun's DISTORTED magnetic field line pattern?
Its uneven rotation.
What is the sunspot cycle? what causes it?
Every 11 years there is a maximum number of sunspots.

This is caused by the solar cycle (22 years) which causes the sun's polarity to change every 11 years.
During sunspot minimums, where do spots appear first?
AT the poles. Then as the poles are about to flip and cause a sunspot cycle max more and more sun spots pop up around the equator.
What causes the heating of the Corona (recall it is hotter than the convection and radiation zones beneath it)?
Electrons and protons are accelerated along the magnetic field lines that cause sunspots causing the heat.
Note that
Sunspots are cool, but the gas above them is hot!
What is a solar prominance?
As a result of electrons and protons accelerating along magnetic fields, the corona is heated. Then gas gets stuck between the B fields and cools causing solar prominences.
Eruptions on the Solar surface resulting from stresses applied to the magnetic field lines, usually near sunspots
Solar flares
Solar flares tend to release energy in what part of the spectrum?
UV and X-rays
Coronal activities (solar flares, solar prominences, sun spots are controlled by magnetic fields) thus they increase and decrease according to what?
the solar cycle. Every 12 years when the poles change, we should get more of all the effects collectively called "CORONAL ACTIVITY".
What is The Proton-Proton Chain?
This is the cause of nuclear fusion and the cause of light on the Sun.
How does The Proton-Proton Chain work?
Recall the sun's core is too hot to have non-ionized atoms (atoms with electrons) so hydrogen atoms (1 proton) combine with eachother and form higher elements UNTIL FOUR HYDROGENS come together to form a helium atom.
But where does the Energy come from that creates the light?
from the loss of mass. 4 hydrogen atoms have more mass than the synthesized helium. THE LOSS IN MASS MAKES A HUGE ENERGY!
How can the small amount of mass lost by the formation of a helium atom cause such a large energy?
According to E=MC^2, a small amount of mass can cause an enormous amount of energy becuase of the c^2 term. (3e8^2).
As we alluded to earlier the sun looses alot of its mass. Will it ever completely disintegrate?
Theoretically yes. However, The sun has enough mass to fuel its current energy output for another 5 billion years!
WHy are such high tempertures required to cause fusion?
because the similar positive charges of hydrogen atoms repel eachother via EMF.
what is one of the byproducts of the fusion reaction?
How do we recieve information from neutrinos?
Neutrinos are almost non-interacting with matter… So they stream out freely.
What is the solar neutrino problem?
Solar Neutrino Problem: Neutrino detectors found only 30 - 50% of the predicted number that were expected from the sun!
What are the results of the inconsistancy?
1) standard model was incorrect or 2) standard particle theory incorrect.
What was the solution to the solar neutrino problem?
In 2002, Sudbury Neutrino Observatory in Canada showed that neutrinos oscillate into different “flavors” during their trip to Earth from the Sun. Previous neutrino experiments only detected one type of neutrino. If all types are accounted for, the total number of neutrinos agrees well with the standard solar model prediction.