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The Solar System

Located at the very center of our solar system, the sun provides us with light that is essential to life on earth.
The sun occupies 98% of the mass of the solar system (Jupiter occupies the majority of the rest) and is the largest object. Though the sun seems very large from earth, it is an average star on the main sequence. It should be noted that the sun isnt the largest star in the universe, it only seems so big because it is so close. The sun's diameter is about 1.4 million kilometres, which makes it large enough for more than 1 million earths to fit in it.
The age of the sun is about 4.6 billion years and it is expected to last 10 billion years in total before it "dies".
Below you can read about features on the surface of the sun, as well as the interior and its atmosphere. There are also astronomical illustrations and space art to view.

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Solar Activity - Space art (P)
Sunspots (P) - Space art (P) - Illustration (P)

Chromosphere - Space art (P) - Illustration (P)
Convective zone - Illustration (P)
Core - Illustration (P)
Corona - Space art (P) - Illustration (P)
Interface layer - Illustration (P)
Photosphere - Space art (P) - Illustration (P)
Radiative zone Illustration (P)


Sunspots appear on the solar surface as dark areas, usually grouped. Though they appear black or very dark, they do emit light, and are not so black: the temperature is about 4 000 degrees kelvin, whereas the surrounding surface has a temperature of 5 800 degrees. It is the contrast that make them appear black... but, what are these dark sunspots?
The sun's activity varies in a period of 11 years (the period is not constant, it varies between 9.5 and 12.5 years), and at the middle of this period the dark sunspots - that actually are magnetic storms - are great in numbers.
At the beginning of the eleven year long solar cycle, the dark spots appear at higher altitudes (+- 45 degrees). At this stage the solar magnetic field is also in order, but as the cycle leaps towards the middle (after about 5.5 years) the sunspots appear only close to the solar equator (+- 5 degrees). The magnetic field of the sun is now in complete disorder and the dark spots, the magnetic storms are great in numbers. The sun could eject massive amounts of charged particles that reach the earth and collide with its atmosphere, appearing as northern/southern light on the top/bottom of earth's hemispheres. The mass ejection could be so violent that it will disrupt the communication between satellites in orbit and earth.
The eleven-year cycle is actually a cycle of 22 years, because during the first eleven year period the magnetic field in the sunspots has one direction in its polarity, and in the following eleven year period, the magnetic field has the reverse direction of polarity. Space art: Sunspots.

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The Core

The core is where the nuclear fusion processes occur. The heat and pressure in this area is so high that hydrogen is fused to become helium. Four hydrogen atoms become two protons, two neutrons, one neutrino and one gamma ray (the two protons and the two neutrons make the helium atom) in a process called "the Proton-Proton chain". More: fusion processes and radiation.
The gamma ray (light) contains an extreme amount of energy, but much of this energy will be lost through collisions with other atoms as the gammay ray travels from the center outwards to reach space.
This area holds about 50% of the sun's total mass. The temperature of the core is about 15 million degrees Kelvin and the density is about 150 g/cm^3 (approximately 10 times the density of gold or lead). The pressure in the core might be as much as 250 billion times the pressure of the earth's atmosphere. The hydrogen burning core extends to about 25% (approx. 175 000 km) of the solar radius. The temperature at the edge of the core is halved and the density drops to 20g/cm^3. Illustration: The core.

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Radiative Zone

The radiative zone extends from 25% of the solar radius to 70% of it. The temperature decreases from 7 million degrees Kelvin to about 2 million K in this zone. Energy (the initial gamma ray) is transported by radiation in this layer, hence the name.
When the gammay ray that originated from the core travel among the atoms, it is absorbed and loses energy as it is re-radiated. Although the gamma ray travels at the speed of light, it will bounce from atom to atom and take about a million year to reach the end of this zone.
In this layer there are mainly ionized atoms: hydrogen, helium nuclei, free electrons. This state of matter is called plasma. Illustration: Radiative zone.

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Interface Layer

The interface layer (Tacholine) is between the radiative and the convective zone. This area is thought to be connected with the solar magnetic field. Illustration: Interface layer.

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Convective Zone

The convective zone is the outer-most layer of the solar interior. It reaches a depth of about 150 000 km. The temperatures are low enough (around 1 million degrees Kelvin) for the atoms to hold on to their electrons. This makes the atoms excited and they bounce around at high speeds. For this reason this layer is called the convective zone. At the surface you can see this convection as the granules. As this gas gets hotter it expands, which makes it move towards the surface (like hot balloons, or bubbles created below a water surface). When it reaches the surface it cools down and sinks again.
Energy is transported much faster in this region than in the radiative zone. The convection zone is sometimes called the "Boiling zone". Illustration: Convective zone.

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The photosphere is just above the convective zone and this is the layer from which the sunlight we see is emitted (the surface and below). It is a thin layer of only a few hundred kilometres of thickness and the temperature is about
6 000 Kelvin. In this layer, which is part of the solar atmosphere energy is once again transported as radiation. Space art: Photosphere, Illustration: Photosphere..

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The chromosphere is 2000-3000 km thick. It glows faintly relative to the photosphere and is very difficult to see apart from when a total solar eclipse occurrs.
The temperature rises from 6 000 K to about 20 000 K. At these higher temperatures hydrogen emits light that gives off a reddish color (H-alpha emission), which can be seen on the prominences which are ejected from the surface. Space art: Chromosphere, Illustration: Chromosphere..

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The corona is an enigmatic area. It is best viewed during a solar eclipse, or with some other object occulting the surface of the sun. The corona is the outmost area of the sun's atmosphere. Astronomers don't know why this area, that is far outside the surface (which is about 5 800 K hot) is so much hotter with temperatures up to 2 million degrees K. According to their theories the temperature might be linked with the magnetic field.
The corona emits light that was at first thought to come from an unknown element, "coronium", because it was not recognized when first observed. However, astronomers could later prove that the radiation came from known elements: iron, nickel and calcium. These elements had lost very many (13+) of their electrons, which tells us that the temperature must be around 1-2 million degrees Kelvin. Space art: Corona, Illustration: Corona.

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Solar Activity

The sun shows it activity in many ways. Sometimes a solar flare is visible, which is a violent explosion in the solar chromosphere or corona. The energy released could be equivalent to more than ten million hydrogen bombs and the temperature is often several million degrees Kelvin. Solar flares can cause "sunquakes", which are really violent seismic events, sometimes measuring up to 11.3 in the Richter scale. During a solar flare all kinds of radiation is emitted, from long-wave radio waves to short-wave gamma rays. Solar flares may take several hours or even days to build up, but the actual flare takes only a matter of minutes to release its energy.
The solar wind is a continuous stream of ions (particularly protons) that radiates outwards from the sun. The solar wind is emitted where the Sun's magnetic field loops out into space instead of looping back into the surface. It takes a few dyas to reach earth and usually has a speed of 400 km/s when it arrives. This solar wind reaches as far as 100 AU (1 au is the average distance between the sun and the earth, 150 million km.) from the sun, effecting the entire solar system.
A prominence is an arc of gas that erupts from the surface, it can be hundreds of thousand kilometres high and last for days. The gas is usually relatively cool. Space art: Prominences.

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Previous: Solar System Creation.
Next: Mercury.


Equatorial Radius: 695 500 km.
Mass: 1.989 x 10^30 kg, about 333 000 the mass of earth.
Density: 1.409 g/cm^3.
Escape Velocity: 617.7 km/s.
Length of day: 25.38 Earth days.
Surface Temperature: 5800 K.

Source: NASA.

Illustration: The sun

Above: The Solar Anatomy.

This illustration is available upon request, as a print (A3-format, 4931 x 3508 px, 300 dpi). It is also available in .PSD (Adobe Photoshop) format, so that it can be customized according to your own desire.

Space art: The Sun

Space art: The Sun in all its' glory.

This illustration is available upon request, as a print (A3-format, 4931 x 3508 px, 300 dpi).

Space Art: Prominence

Space art 2: A wide prominence stretching across the surface.


All content Copyright , 2005- by Fahad Sulehria, unless stated otherwise.
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