Saturday, February 26, 2011

Our Sun - A Closer Look

In this section, we will discuss some of the more prominent features of the Sun. And we will also discuss the Solar Eclipse (found on its own page).

Here is a nice summary of some of the important features. Just click on the image to see a large version. The layers in this image is not to scale.

Corona This outer layer is very dim - a million times dimmer than the photosphere and oddly enough, it is the hottest. At 106 K it would seem the heat would be unbearable for us, but remember in Physics heat is a measure of molecular energy - the movement of molecules within a space. Because the Corona extends several million kilometers into space, there is a lot of room for molecules to move. It is this movement that is the source of the solar winds. The high temperature of the Corona can force ions to move as fast as a million kilometers per hour.
Chromosphere Chromosphere means "sphere of color," but this layer is 10-4 as dense as the photosphere so it is not that bright. In fact, the best way to view the chromosphere it to use a special narrow band filter called a Hydrogen-Alpha (Hα) filter. The wavelength is 656.3 nm which is in the red (lower energy) part of the spectrum. This wavelength is given by the single electron in the Hydrogen atom dropping to the second orbit (more in the physics section). The temperature of the inner portion of this layer is lower (at 4400 K) than the photosphere, but jumps suddenly to 25,000 K. From this point to the transition into the Corona, the temperature jumps sharply to 400,000 degrees. The reason for this is not clearly understood and remains an active subject to Astronomers studying the Sun, but suspect the magnetic flux as a result of (as well as resulting in) sunspot formation might provide some clues.
Photosphere The Photosphere, Chromosphere and Corona are the three layers that make up the "atmosphere" of the Sun. The Photosphere is the inner-most layer and is the layer we easily see every day. It burns at 5800 K. Oddly enough, the photosphere is opaque to light, only allowing transferred energy from the convection layer below. It is the opaque feature of the photosphere that shields us from directly viewing the thermonuclear core and provide the shape of the Sun. The transferred energy from the convection zone below occurs in the form of granules (see the photo above). As the hotter gas rises up, the cooler gas descends only to be re-heated by the convection layer and the process repeats itself. Sometimes disturbances in the magnetic field will produce sunspots, which occur within this layer, but more on that later.
Convective Zone We cannot visualize past the photosphere, but we can create models and examine particles emanating from the Sun to get an idea to the Sun's interior structure. Three internal layers dominate the anatomy with the outer layer (just under the photosphere) called the convective zone. Radiation is not an effective mean of generating the heat energy produced by the core, so the convective layer acts as the buffer to stabilize this energy. Once a photon enters the convective zone, it can take 170,000 years for it to reach the photosphere. The action of the photon is something called the "random walk" where the photon collides with other photons mainly because the opacity of this zone it a bit high. While there is some pretty unforgiving mathematics involved in determining exactly how much opacity there it, it is important to know the convective zone helps maintain the hydrostatic equilibrium within the Sun by acting as a buffer.
Radiative Zone This layer of the Sun is responsible for delivering the photons from the Core to the Convective layer. The radiative layer "radiates" the energy by the emission and reabsorbtion of photons.
Core The heart of the Sun is the core. Not much to say here accept the gravity was strong enough to bring Hydrogen together to initiate fusion. The magic temperature for fusion is 10,000,000 K. The energy released is balanced by the radiative and convective layers of the Sun to create the hydrostatic equilibrium necessary to prevent the Sun from flying apart or to burn its fuel to fast.

Our Sun - A Closer Look

In this section, we will discuss some of the more prominent features of the Sun. And we will also discuss the Solar Eclipse (found on its own page).

Here is a nice summary of some of the important features. Just click on the image to see a large version. The layers in this image is not to scale.

Corona This outer layer is very dim - a million times dimmer than the photosphere and oddly enough, it is the hottest. At 106 K it would seem the heat would be unbearable for us, but remember in Physics heat is a measure of molecular energy - the movement of molecules within a space. Because the Corona extends several million kilometers into space, there is a lot of room for molecules to move. It is this movement that is the source of the solar winds. The high temperature of the Corona can force ions to move as fast as a million kilometers per hour.
Chromosphere Chromosphere means "sphere of color," but this layer is 10-4 as dense as the photosphere so it is not that bright. In fact, the best way to view the chromosphere it to use a special narrow band filter called a Hydrogen-Alpha (Hα) filter. The wavelength is 656.3 nm which is in the red (lower energy) part of the spectrum. This wavelength is given by the single electron in the Hydrogen atom dropping to the second orbit (more in the physics section). The temperature of the inner portion of this layer is lower (at 4400 K) than the photosphere, but jumps suddenly to 25,000 K. From this point to the transition into the Corona, the temperature jumps sharply to 400,000 degrees. The reason for this is not clearly understood and remains an active subject to Astronomers studying the Sun, but suspect the magnetic flux as a result of (as well as resulting in) sunspot formation might provide some clues.
Photosphere The Photosphere, Chromosphere and Corona are the three layers that make up the "atmosphere" of the Sun. The Photosphere is the inner-most layer and is the layer we easily see every day. It burns at 5800 K. Oddly enough, the photosphere is opaque to light, only allowing transferred energy from the convection layer below. It is the opaque feature of the photosphere that shields us from directly viewing the thermonuclear core and provide the shape of the Sun. The transferred energy from the convection zone below occurs in the form of granules (see the photo above). As the hotter gas rises up, the cooler gas descends only to be re-heated by the convection layer and the process repeats itself. Sometimes disturbances in the magnetic field will produce sunspots, which occur within this layer, but more on that later.
Convective Zone We cannot visualize past the photosphere, but we can create models and examine particles emanating from the Sun to get an idea to the Sun's interior structure. Three internal layers dominate the anatomy with the outer layer (just under the photosphere) called the convective zone. Radiation is not an effective mean of generating the heat energy produced by the core, so the convective layer acts as the buffer to stabilize this energy. Once a photon enters the convective zone, it can take 170,000 years for it to reach the photosphere. The action of the photon is something called the "random walk" where the photon collides with other photons mainly because the opacity of this zone it a bit high. While there is some pretty unforgiving mathematics involved in determining exactly how much opacity there it, it is important to know the convective zone helps maintain the hydrostatic equilibrium within the Sun by acting as a buffer.
Radiative Zone This layer of the Sun is responsible for delivering the photons from the Core to the Convective layer. The radiative layer "radiates" the energy by the emission and reabsorbtion of photons.
Core The heart of the Sun is the core. Not much to say here accept the gravity was strong enough to bring Hydrogen together to initiate fusion. The magic temperature for fusion is 10,000,000 K. The energy released is balanced by the radiative and convective layers of the Sun to create the hydrostatic equilibrium necessary to prevent the Sun from flying apart or to burn its fuel to fast.

Our Sun

At the heart of our Solar System is the Sun. Every day, the Sun rises and sets and ancient astronomers used this consistency to erect temples to predict seasonal changes for the harvest. The warmth of the Sun is vital to life on Earth because of photosynthesis and its warmth heats the surface to help with weather changes. But what is the Sun made of? How does the Sun generate its energy? Will the Sun shine forever? The answers are within....

Image of Sun in white light Mean Distance from Earth: 149,598,000 km
Mean angular diameter: 32 arcmin
Radius: 696,109 km
Mass: 1.9891 x 1030 kg
Composition: 74% Hydrogen
25% Helium
1% Other
Mean Density: 1410 kg/m3
Mean Temperature: 5800K
Luminosity: 3.86 x 1026 Watts
Orbit about Galaxy: 220 million years
Orbital Speed: 220 km/s

Solar System Formation

Everything has a beginning, and our story begins when the cloud that was the Solar Nebula began to contract. All stars exist in islands called galaxies, and galaxies contain old and new stars as well as clumps of dust clouds. These clouds contain mostly hydrogen and some heavier metals (any elements that are heavier than helium is considered a metal by Astronomers). As we will learn the the Sun section, stars create their energy by a process called fusion. When a star ends its life, it explodes in a tremendous phenomenon called a supernova. A supernova has so much energy that heavy metals are formed - metals like iron and gold. These elements "seed" surrounding hydrogen clouds so that newer stars will contain more heavy elements in their atmospheres.

It is believed that for a system of planets to form around a star during cloud contraction the cloud must contain heavy elements.

The Exploded Planet Hypothesis

he Exploded Planet Hypothesis (EPH) offers an alternative explanation for the origin of the asteroid belts and comets. For an overview, see Tom Van Flanders's book Dark Matter, Missing Planets & New Comets or read the updated summary posted here, "The Exploded Planet Hypothesis -- 2000". There are presently three known explosion mechanisms.

Far from being a new idea, the EPH fell out of favor with mainstream scientists, primarily for lack of a viable causal theory. However there is a growing body of evidence that suggests planetary explosions may not even be uncommon (see "A Revision of the Exploded Planet Hypothesis"). While most astronomers believe the solar system has remained essentially unchanged since its formation, "The Original Solar System" and "Origin of Trans-Neptunium Asteroids" offer a very different perspective.

Consistent with our mission statement, the EPH makes falsifiable predictions. One way the EPH has distinguished itself from competitive theories is in predicting that many comets and asteroids will have satellites. The satellites of comet Hale-Opp, discovery of the asteroid Ida's moon Dactyl, and the "Near Challenge Results" are all examples of the success of this genuine prediction.

The EPH was recently used to make exceptionally accurate predictions of the November 1999 Leonid meteor storm, as well as for the two subsequent years. See the complete 2000 and 2001 predictions. This same methodology also predicted another Leonids storm in 2002 as well as a Perseid storm in 2004.

Finally, because the EPH offers a simple explanation for the sudden and dramatic pole shifts on Mars and the crustal dichotomy of the planet, the EPH has been connected with the Caledonia story.

Solar Eclipse

There are four types of solar eclipses: total, annular, hybrid, and partial. The occurrence of each solar eclipse as per observer will depend on three main factors: the position of the Earth and Moon along their orbital paths (i.e., whether near its apogee, near its perigee, or somewhere in between), the location of the observer on Earth, and the alignment between the Earth, Sun, and Moon.

In this article, we'll focus on the effect of the positions of the Earth and Moon along their orbital paths. Their positions will determine whether the eclipse witnessed by an observer on Earth will be total, annular, or hybrid.

Recall that the Earth's and Moon's orbits are elliptical in shape. That means, in some instances, the Earth can be at its farthest position from the Sun (known as its apogee), while in others, it can be at its nearest (perigee). In still other instances (in fact, more frequent than the other two), the Earth can be located somewhere in between the two extremes.

When the Earth is at its farthest, the Sun will naturally appear smallest to an observer than if the Earth were at its nearest. Hence, all things considered equal, the Moon will be able to cover a greater part of the Sun when the Earth is at this position.

Now, since the Moon's orbital path about the Earth is also elliptical, there should be a position wherein the Moon will appear largest – its perigee. The nearer the Moon, the bigger it will appear from an observer on Earth, and the bigger its obstruction (if ever) of the Sun. As we can see, the positions of the Earth and Moon along their orbital paths are crucial in producing the type of solar eclipse.

So, at which extreme positions of the Earth and Moon can we have the smallest Sun and largest Moon?

The Sun is smallest when the Earth is at its apogee while the Moon is largest when the Moon is at its perigee. Thus, if these two scenarios happen at the same time while the Earth, Sun, and Moon are fully aligned, many of us will experience the most total solar eclipse there can ever be.