Welcome to Cheshire Starwatch | |
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Stardate 09:28:97
Our
local star offers Earth bound observers not only beautiful views of large
flares rising from the surface of the Sun, and cool, dark sunspots, but
also the chance to do astronomy another 12 hours a day!
Safety in solar observing cannot be over stressed! Galileo himself went blind from observing the Sun. Today, there are many safe solar filters available on the market, and a few potentially dangerous ones.
The general rules for choosing a good, effective solar filter are to only use ones which filter the light before it ever enters the telescope, and to never look through your finderscope when viewing the Sun. Any solar filter which fits into the eyepiece end of a telescope should never be used.
Last week's article discussed the various designs in solar filters, and anyone interested in beginning to observe the Sun should either read last week's article, or access the article on the World Wide Web at www.tmclark.com/Starwatch/starwatch.html. It contains information which will guide you towards a safe, rewarding new addition to the wonderful hobby of astronomy.
If we are going to start observing our parent star, we should know a little about the star we call the Sun. It measures 1,392,000 km (870,000 miles) across. This is about 109 times the diameter of the Earth. The Sun also contains 99% of the mass of the solar system, nearly 2(8)10(6)30 kilograms (about 9.9(8)10(6)30 pounds). This would be 2 with 30 zeros after it, or 99 with 29 zeros after it. The escape velocity from the surface of the Sun (The speed at which you would have to travel in order to escape from the surface of the Sun) is nearly 618 km (386 miles) per second! Compare this with the Earth, which has an escape velocity of a comparatively meager 11.2 km (7 miles) per second.
The outermost layer of the Sun is called the photosphere, and although it is only 500 km (about 312 miles) thick, this is the region where most of the light from the Sun is produced. After energy is produced at the core of the Sun, it is continually downshifted (it is changed to a lower frequency) on it's way towards the surface of the Sun. The dominant wavelength of radiation from any body is determined strictly by the temperature of the surface of the body. For a body with a surface temperature of the Sun, we can determine that the dominant wavelength of radiation emitted is in the visible part of the spectrum, between the wavelengths of yellow and green light. Because we see yellow easier than we see any other color, including green, the Sun appears, to the human eye, to be yellow.
The main form of energy produced at the core of the sun, however, are nuetronios. They are nearly massless, elusive particles which react with almost nothing they encounter. When the first nuetronio detectors were set up they reported finding no nuetronios at all! Recent experiments still only detect about 1/3 of the nuetronios expected. Either at least some of our ideas about nuclear reactions are wrong, our idea of the nuetronio is wrong, or the Sun died a million years ago.
That last idea would not only be tragic for humanity and the world at large, but it would also blow our theories of stellar evolution!
It is from the photosphere that we see gigantic flares erupt, with the force of millions of nuclear weapons. The flares are almost certainly linked with the magnetic field of the Sun, as are the sunspots. Part of the evidence for this conclusion is that flares always occur around areas of sunspot activity.
Sunspots, always occur in pairs, with one sunspot having a north polarity, and the other, south. They also always form near the equator of the Sun, and slowly migrate towards the polar regions of the Sun. They seem to be formed by the fact that the Sun rotates faster at it's equator than it does at the poles, stretching the lines of magnetic force until they break, leaving two magnetic areas with opposite polarities, similar to breaking a bar magnet in two.
Next week, we will look more closely at sunspots, and solar flares.
Clear skies, and good viewing.
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