and we've got to get ourselves back to the Garden."
- Joni Mitchell
The Sun
Diagrammatic view of the Sun
The Sun is (obviously) the most prominent feature in our solar system. It's the largest object, consisting of approximately 98% of the mass of the whole solar system. Nearly one hundred and ten Earths would be required to fit across the Sun's disk, and its interior could hold over 1.3 million Earths.
The Sun's outer visible layer is called the photosphere and has a temperature of 6,000°K (5,800°C or 11,000°F). This layer has a mottled appearance due to the turbulent eruptions of energy at the surface. Energy generated in the Sun's core takes a million years to reach its surface.
Solar energy is created deep within the core of the Sun. Here the temperature 15,000,000°K (27,000,000°F) and a pressure of 340 billion atmospheres is so intense that nuclear fusion reactions can take place. One of these reactions causes four protons, or hydrogen nuclei, to fuse together to form one helium nucleus, or alpha particle. The helium nucleus is about 0.7% less massive than the four protons it took to make it. The difference in mass is emitted as energy and is carried to the surface of the Sun, through convection, where it is released as light and heat.
Every second, 700 million tons of hydrogen are converted into helium ashes. In the process, the equivalent of 5 million tons of pure energy is released. So, as time goes on the Sun is becoming lighter.
There are other fusion cycles taking place within the core of the Sun. Some of those cycles convert the helium into successively heavier nuclei, such as oxygen, carbon, nitrogen, calcium, silicon, and more... right on up to iron. The elements that make up the Earth, all that we breathe and all that we eat and everything in our bodies came from those fusion processes.
We truly are stardust.
Solar Statistics
Mass (kg) ......................................... 1.989x1030 Mass (Earth = 1) .................................... 332,830 Equatorial radius (km) .............................. 695,000 Equatorial radius (Earth = 1) ........................ 108.97 Mean density (gm/cm3) ................................ 1.410 Rotational period (days) ............................. 25-36* Escape velocity (km/sec) ............................. 618.02 Luminosity (ergs/sec) ............................. 3.827x1033 Magnitude (Vo) ........................................ -26.8 Mean surface temperature ............................ 6,000°K Age (billion years) ..................................... 4.5 Main chemical (elemental) composition Hydrogen .......................................... 92.1% Helium ............................................. 7.8% Oxygen ............................................. 0.061% Carbon ............................................. 0.030% Nitrogen ........................................... 0.0084% Neon ............................................... 0.0076% Iron ............................................... 0.0037% Silicon ............................................ 0.0031% Magnesium .......................................... 0.0024% Sulfur ............................................. 0.0015% All others ......................................... 0.0015%
* The Sun's period of rotation at the surface varies from approximately 25 days at the equator to 36 days at the poles. Deep down, below the convective zone, everything appears to rotate with a period of 27 days.
Here are a few images of the Sun as seen in different wavelengths of light...
 Visible light |
 Hydrogen alpha light |
 Ultraviolet light |
 X-Ray light |
This next set were all taken the same day, January 20, 1995... the Magnetogram shows differences in magnetic field strength... compare the images as seen in different wavelengths of light... look for similar features...
 Magnetogram |
 Infrared Helium light |
 Hydrogen alpha light |
 X-Ray light |
The first image in this series is a solar flare closeup in Hydrogen alpha light... the next is a modest coronal mass ejection... and the last is a composite of images in various wavelengths. These images, taken March 7, 1996, by the Solar and Heliospheric Observatory (SOHO), show (bottom) magnetic fields on the sun's surface near the south solar pole; (middle) an ultraviolet image of the 1 million degree plumes from the same region; and (top) an ultraviolet image of the quiet solar atmosphere closer to the surface.
 Flare in Hydrogen alpha light |
 Coronal mass ejection |
 Solar plumes |
We plan to put up more images as time permits... we now have enough images for a full UV gallery, XRay gallery and some other spectacular shots.
