1. The Sun and Eclipses
Notes

2. The Sun’s Interior
The sun contains about 99.8% of the entire mass of the solar system.
The sun does not have a solid surface. The sun is a ball of gas that glows. About 3/4 of the sun’s mass is hydrogen gas. About 1/4 of the mass is helium gas.
The sun’s interior consists of the core, radiation zone, and the convection zone.

3. One Hydrogen Atom
One Helium Atom
One proton
Zero neutrons
An element is
defined by the
number of
protons it
contains.
Two Protons
Two neutrons

4. The Sun’s Interior
The center of the sun is called the core. The sun produces energy at its core. The sun’s energy comes from nuclear fusion. In nuclear fusion, hydrogen atoms joins together to form helium.

5. The Sun’s Interior
The middle layer of the sun is called the radiation zone.
The radiation zone is a region of very tightly packed (dense) gas where energy is transferred mainly in the form of electromagnetic radiation.

6. The Sun’s Interior
The outer layer of the sun is called the convection zone. Streams of gas move energy toward the sun’s surface.
In the convective zone, extremely hot gases move freely in cells that will travel towards the surface then cool off (relatively speaking) and sink back towards the core.
This process is known as convection.
It’s the same process that gives us the phrase, “warm air rises.”

8. The Sun’s Atmosphere
The sun’s atmosphere consists of the photosphere, the chromosphere, and the corona.
The innermost layer of the sun’s atmosphere is the photosphere. Photo means “light.” The photosphere means the sphere that gives off visible light.
When you look at an image of the sun, you are looking at the photosphere.

9. The Sun’s Atmosphere
The middle layer of the sun’s atmosphere is the chromosphere.
This layer is only visible during a total solar eclipse, when the viewer is in the umbra of the eclipse.
The chromosphere is a faith red glow around the photosphere during an eclipse.
Chroma means “color,” so the chromosphere is the “color sphere” of the sun.

10. The Sun’s Atmosphere
The outer layer of the sun is known as the corona.
This too is only visible during a total solar eclipse.
During a solar eclipse, the corona appears to be a large white halo surrounding the blackness of the moon.
Corona means “crown.”
As the corona extends into space for millions of kilometers, it gradually becomes so thin, it only consists of electrically charged particles called the solar wind.

13. Features of the Sun
The sun’s surface is neither flat, nor inactive. Scientists have spotted a variety of features that occur either on, or just above the surface of the sun.
Early in the observation of the sun, scientists noticed that there were darker spots on the surface. These came to be known as sunspots.
They may look small, but many can be larger than Earth.

15. Features on the Sun
Sunspot are actually areas of cooler gases on the sun’s surface. These areas move and have a regular cycle of 11 years, where they will grow and seem to disappear.
Sunspots were even used to prove that the sun rotates on an axis much the same way Earth does.

16. Features on the Sun
A prominence is a huge loop of gas that links different areas of sunspots and is connected to fluctuations of the sun’s magnetic field.
A solar flare is an explosion of gas from the sun’s surface out into space, usually associated with a massive release of magnetic energy.

17. Features on the Sun
Solar flares can greatly increase the solar wind from the corona, resulting in an increase in the number of particles reaching Earth’s upper atmosphere.
Normally, Earth’s own magnetic field blocks these particles, but there are weak spots in our “force-field” at the North and South Poles.
When solar winds enter our atmosphere through these weak spots, it causes out atmosphere to glow, creating massive sheets of colors that cover the skies. These are known as auroras.
Auroras in the northern hemisphere are called the Aurora Borealis and auroras in the souther hemisphere are called the Aurora Australis.

20. Features on the Sun
Because solar winds interact with Earth’s magnetic field, it can create something known as magnetic storms.
These storms within our magnetic field have the ability to disrupt radio, telephone, and television signals. It can break down the electrical grid and fry satellite circuitry.
On March 13, 1989 a severe geomagnetic storm caused the collapse of the Hydro-Québec power grid in a matter of seconds as equipment protection relays tripped in a cascading sequence of events. Six million people were left without power for nine hours, with significant economic loss. The storm even caused aurorae as far south as Texas.

21. Eclipses
An eclipse is when an object in space comes between the sun and another object.
Eclipse - to cover up
When Luna’s shadow hits Earth or Earth’s shadow hits Luna, an eclipse occurs. A solar eclipse occurs when the moon passes directly between Earth and Sol, blocking sunlight from Earth.

24. Eclipses A lunar eclipse occurs when Earth is between Luna and Sol.
In a lunar eclipse, Earth’s shadow hits the moon.
A lunar eclipse occurs when there is a FULL MOON.

27. Eclipses
So why is there not a solar and lunar eclipse each time we have a NEW MOON and FULL MOON?
The moon does not lie in a straight line between Earth and Sol. It is tilted about 5° from the ecliptic. Because of this tilt, eclipses are much rarer than expected.