Séo Sunne is swíðe gréat þóðer swíðe hátes gesweorces, mǽst hydrogen and helium. It is the power house of the Solar System. It's our nearest star. Scientists can tell what is going on inside a star from its color. Wiþútan þǽre sunnan næfde séo Eorðe life. We depend on the sun for energy.
Hú gréat is séo sunne?
Séo sunne is swíðe gréat - swíðe gríetre þonne séo Eorðe! Héo is 1,392,000 km oþþe 109 Eorðena ofer, and hæfþ má þonne 99.9% þǽre sunnlican endebyrdnesse hefignesse. Gif þu ǽnige þinga cúðe standan on þǽm oferblican þǽre sunnan, If you could somehow stand on the surface of the Sun, wǽge þu 28 síðum swá micel. Geþungen mann wǽge swá micel swá wægn.
More than a million Earths could fit into the volume of the sun! It doesn't look that big from where we stand, though. That's because the sun is about 150,000,000 km away. At that distance, it takes light from the sun over eight minutes to reach the Earth. Compared to other stars, the sun is about average-sized.
What happens inside the sun?
The sun is the main source of energy for the earth. This energy is released deep within the sun in a process called atomic fusion. Four hydrogen atoms are fused together to make one helium atom. The helium atom has slightly less mass than the four hydrogen atoms; the extra mass is converted to energy. This is the same way energy is released in a nuclear bomb called a hydrogen bomb. The diagram below shows what scientists think is going on inside the Sun. The colours are to show the different regions.
|Sēo Sunnlice Endebyrdnes
Core: The center of the Sun is very dense. It's about 12 times as dense as lead. It's also very hot - about 15 million °C. This region is where most of the nuclear reactions are taking place.
Radiation Zone: In this zone the light, heat, and X-rays produced in the core fight their way out towards the surface. The gases that make up the zone are still very dense and keep absorbing and emitting the rays. Have you ever tried to run through water? That's what it's like for light waves in this region of the sun. It can take a single ray of light a million years to make its way out of this zone.
Convection zone: Have you ever seen the air shimmer above a fire? Perhaps you've been told it's because "heat rises"? Well actually heat doesn't rise all by itself. It is the hot air that is rising. Hot gases tend to rise, cold gases tend to sink. In this outer region of the sun the gases are less dense and so behave more like ordinary gases that we see on Earth. At the bottom of the convection zone the gas gets heated up by the energy that is coming through the radiation zone from the core. This gas rises up to the surface of the sun where it gives up its heat and cools down. The now cold gas then sinks back down. The plumes of rising hot gas and sinking cool gas together form huge ribbons of circulating gas known as "convection cells".
Hwæt sind sunnspeccan?
Sunspots are slightly cooler areas on the surface of the sun that appear as dark areas. They only appear dark against the brightness of the rest of the surface of the sun. Despite their appearance, they are still extremely bright — brighter than an electric arc. The number of sunspots seen rises and falls over an 11 year cycle.
Sunspots appear when the Sun's magnetic field is concentrated, impeding the flow of energy. A typical sunspot consists of a dark region, called the Umbra, surrounded by a lighter region, called the Penumbra. The Umbra is about 2000 °C (3600 °F) cooler than the photosphere and only looks dark in relation to its surroundings. Spots usually form in groups which are carried across the solar disk by the Sun's rotation.
Over a period of about 11 years, sunspot numbers increase before decreasing slowly. This sunspot cycle happens at about the same time as the increase and decrease in the Sun's overall activity.
The most complex sunspots are hubs of intense magnetic fields. These active regions can suddenly erupt as flares that are short-lived, extremely bright areas that release large amounts of charged particles and radiation. Flares are more prevalent during peaks in solar activity.
What is the solar atmosphere like?
The part of the sun that you see in the sky is called the photosphere. This is where the pressure from the gases inside the sun is low enough that they no longer glow so bright, and is generally considered the "surface" of the sun. Everything that is below the photosphere gives off light. The photosphere is also the very top of the convective zone of the sun. It is on the photosphere that you see sunspots.
While you can say that the atmosphere of the sun begins at the photosphere, in reality the entire sun is one very large ball of gases, where there is no definite beginning or end to the gases from the Sun. Because the Sun is so hot, gases from the sun are constantly streaming outward and form various parts of the solar atmosphere, which extends beyond even the orbit of Pluto. These gases near the Earth are very thin, with so little in the way of gas pressure that you can basically call it a vacuum, but it still is enough that it pushes away gases from other stars in our galaxy. It is only until you get to the heliopause that you can say that the influence of the Sun's atmosphere ends.
Various parts of the solar atmosphere are as follows:
Næssas and Sunnlica Fýrtungan
When you look at the sun through a telescope (with special filters so you eyes don't get damaged!), at the sides of the photosphere there appear to be large eruptions of gases like it was from a volcano. Each of these is called a prominence. There have been several kinds of prominences, but all of them are very large. Ones you can see are hundreds of kilometers long, and the largest was almost 400,000 kilometers. That is almost twice as far as the moon is from the Earth. These prominences are related to sunspots, because they are often seen as coming from a sunspot. The largest of these prominences sometimes become so large that they leave the sun entirely, and that is when they become a solar flare.
When early astronomers viewed the sun during an eclipse, they noticed that there was a brief flash of light immediately before and after the eclipse. Instead of being a steady white light, it seemed to be a rainbow spectrum of all of the colors you can see, which is what gives the chromosphere its name. It is not as bright as the photosphere, which is why you normally don't see it during the day, but only during an eclipse.
Even more faint than the photosphere or chromosphere is the corona. This is a region extending from the chromosphere and gradually becoming a part of the solar wind throughout the rest of the solar system. The reason why the corona glows is because the gases in the corona are actually hotter than the surface of the Sun! The reason why this happens is still a mystery to scientists, but there are several theories for what is happening. The corona will shift and change, sometimes very rapidly over minutes or hours, due to changes from the sun itself. Because the photosphere is so bright, it is difficult to observe the corona except during an eclipse even with advanced scientific instruments. Some telescopes in space are making it easier to observe the corona, but it is still something that scientists are trying to understand.
Swá se coróna gǽþ furðor of þǽre sunnan, "blǽwþ" hé forþ ongéan eall þára planétena in þǽre sunnlican endebyrdnesse. Þés hátte man se sunnlica wind. While the gas pressure is very low, it still is enough that some very light objects and other gases are pushed away with the solar wind. For other astronomical object, this is visible with the two comet "tails", where one "tail" is mainly rocks and dust, with the other "tail" composed of gases. This second tail is being pushed by the solar wind and causes its effect.
In 1960, the Satellite Echo I entered orbit and was one of the largest satellites ever put into space, in terms of volume. Basically it was a large ballon that was inflated by a small amount of gases inside. Because it was so light but also very large, its orbit was substantially affected by the solar wind and other solar pressures. Even more compact satellites still have to take solar wind into account when planning orbits and how long a satellite will stay in orbit.
In the future, solar sails will use the solar wind and light pressure in order to travel between planets, where spaceships use sails instead of just using rocket engines.
If you travel to a place very far away from any cities and look up at the night sky, a very faint glow will come from a band across the sky in roughly the same part of the sky that you see the other planets. This is not the Milky Way, which is also visible, but even more faint than that. This is actually sunlight which is reflected off of dust and meteoroids that are found throughout the ecliptic plane. This dust is the remains of comets and asteroids colliding with each other and eventually falls into the sun over millions of years.
Þǽt Sunngemǽre is þæt þe man cann hátan þá ecge þǽre sunnlican endebyrdnesse. This is where the solar wind slows down and stops (or "pauses") due to the "solar wind" coming from other stars in the galaxy. There is a region just inside the heliopause where the solar wind slows down from supersonic speeds (literally, faster than sound) to subsonic speeds. This creates a slight jolt in the electrical systems of spaceships that was detected by the Voyager I spaceship in May 2005, which was the first man-made object to ever travel this far from the Sun. Since this is so far from the Sun, this is a part of astronomy that scientists are still trying to study and there is much more that needs to be learned about this part of the solar system.
Hwæt is sunnlic weder?
Solar weather is a new science, but something that has a huge impact on a number of things here on the Earth. When a solar flare is produced on the sun, it includes a large amount of plasma, or very hot gases. If this flare then heads toward the Earth, it will cause a number of problems, including blackouts on electrical power systems in large cities, communications disruptions with radio transmitters and satellites, and potentially even death if an astronaut is caught unprotected when a large solar storm comes from that flare. Normally the Earth's atmosphere protects you and I from direct effects of these flares.
These solar flares also cause something called an aurora. This is also known as the "Northern Lights" or "Southern Lights" (depending if you are closer to the north or the south pole) where the plasma interacts with the atmosphere of the Earth and the Earth's magnetic field. Normally you can only see this event when you are close to one of the poles, but sometimes a very powerful solar flare will produce an aurora that can be seen as far south as Mexico, or as far north as Southern Brazil, or South Africa.
The aurora is not unique to the Earth either. Aurora have been seen on all of the planets except for Mercury and Pluto by telescopes and space probes. The aurora on Pluto have not been seen because it is so far away and no space probes have ever been there, and Mercury doesn't have an atmosphere (that is substantial).
Just like there are weather forecasts for weather on the Earth, there are weather forecasters that study solar weather and try to predict when solar storms will come. Not only do they study just what will happen near the Earth, but they also try to predict what is going to happen in other parts of the solar system as well. As more space missions go into other parts of the solar system, this will become even more important. To help make the predictions, they also study the sun itself, and try to determine in advance when a solar flare will occur.