...we really have no idea what stars and asteroids are made of. We BELIEVE that stars are a nuclear reaction of hydrogen and helium, but we really do not know for sure.
Well, in the sense that nearly everything we think we know we only know by faith, there is truth there. However, we have some pretty solid evidence supporting our theories concerning the material makeup of stars.
Let's start by heating a piece of iron. You're all roleplayers; you can imagine this. It starts to glow red. But it doesn't glow "red" in a general sense, it glows a very specific shade of red defined by a single specific frequency of red light. It gets brighter as it gets hotter, and what is happening is that the heat exciting the iron atoms is causing those atoms to release photons of a specific frequency that is defined by the structure of the iron atom. Then, as the temperature increases and we see the color of the glow shift, that red is not changing--but it is being joined by the release of photons of other very specific individual frequencies. Our vision system is designed to combine all of these and round them to the nearest "color"--and to ignore electromagnetic "light" that is outside a very narrow range that constitutes our visual perception. However, we have the ability, using prisms as the simplest way, to separate the light into individual frequencies, each frequency appearing as a narrow bar of color.
That's what a spectroscope does: it separates light into the rainbow of those colors actually being emitted by the light source. If the light source is a heated piece of iron, it will have very specific bars of light at very specific frequencies.
And that is true for every atom, that when excited sufficiently it glows. That's how we make lights. Further, the glow of each element is unique to that element, and each gains additional frequencies at specific temperatures, and the ratios of of those frequencies depends on the temperature. Further, having studied the matter, we can calculate and predict the frequencies specific atoms will release at specific temperatures.
Thus we can work backwards: if we can capture the light from a light source, we can split it into all the frequencies (visible and invisible) it contains, identify each and the relative intensities of each, and match these to the elements which must be present and the temperature at which they would be emitting those "colors". We thus have a very accurate measuring stick for determining the composition of a star.
A few trivial details are interesting.
Iron is the heaviest element (the largest nucleus) which can be produced by compression within a star. When all (or most) of the matter in a star has been fused into iron, the process stops, and the star is dead. Elements heavier than that are considerably more rare in the universe for precisely that reason--it is simple for iron to form in stars, and eventually to be smashed off into the universe. To get heavier elements, you need a nova or supernova--an explosion of a star. In the force of such an explosion, some of the material is compressed by fusion into elements of greater atomic weight.
The bands of elements found in stars are specific enough that we can use them to detect relative motion of the stars by use of the Doppler Effect. You probably remember that as the reason why a train whistle sounds high when the train is coming at you and drops in pitch when it passes: the frequency of the wave is compressed or decompressed by the movement of the source relative to the receiver. However, all frequencies are compressed or decompressed by the same proportion. Thus we find that the light from some stars have bands that are correctly spaced for certain elements but are all too high or too low. This then suggests, respectively, that the source is moving toward or away from us at sufficient velocity to shift the bands that amoung--and we can determine exactly what velocity is necessary to create a shift of that degree.
If I send two pings from my sonar and it reflects back at me, my system will show that it bounced off a smooth hard surface with a regular curve which is moving through the water, and I will realize that I have found something artificial, probably a submarine. I then "know" that the submarine is there. I have not seen it; I have not been to it. I have, however, received information that proves its presence, position, and movement. In the same way, I have not brought back material from the stars, but they have sent rather detailed information as to their temperature and composition and movement based on the light radiating from them.
Thanks for the opinions on the gems. I'm still thinking about it.
--M. J. Young
