Astronomy for the layman; The sun in action

The National Association of educational broadcasters with the cooperation of the California Academy of Sciences and radio station KPFA in Berkeley presents a program in the recorded series astronomy for the layman on today's program Leony Sellon a lecturer in astronomy at the Morrison Planetarium of the academy and John Hopkins an inquisitive layman discuss the sun and action sunspots solar prominences and other eruptions. Mr. Hopkins begins the discussion we take for granted the light and heat of the sun or we know printed for the past half century since the Smithsonian Institution has been making systematic Mazie of the sun's output. There's been no perceptible diminution. That of course also theory tells us that this must have been so for millions of years will be so for millions of years to come. But Leo I also know there are various short

term variations in the output from the sun. I'd like to discuss some of these at this time for example the sunspots whose existence I guess even the Chinese apparently knew many years ago. These are relatively cooler areas and shouldn't they affect the amount of heat you receive from the sun. Well in principle they certainly should and they do but the percentage involved is quite small. And by measuring the actual heat received here at the surface of the earth and correlating it with sunspots the numbers that appear on the disk of the sun at various times it's been found I think that the variation cannot exceed want to 2 percent. Some small quantity of that kind and it's quite erratic for as you can see a number of sunspots is a variable thing and not all uniform and the changes will be a fairly capricious at least that may be the first impression until we investigate a little more about it. I see. It's just the question of really they do

make a difference but it's so small that you can't measure it it's not big enough to be of any great consequence to us. I think the latter part of your statement is correct that hardly large enough to be of any consequence. But we do know for example that when there are many sun spots on the disk of the sun that ultraviolet radiation tends to be a little more intense that isn't in proportion to the rest of the spectrum. This may seem a little strange since ultraviolet light is generally associated with an increase of energy. So how is it that dark spots in the sun should bring this about. I think probably dealing with something is fairly complicated the sunspots are probably a manifestation of some greater energy being released in the sun which in its own way and then I face itself again has a more ultraviolet light. But whether this is so or not it's just a matter that we must understand the sunspot phenomenon is fairly complicated. Maybe you ought to talk a little bit though about the sunspots themselves and what they really are some of our listeners may

have only a vague notion of this. Well I remember. Time passed. We have discussed a little bit about them and you did say they were cool or what. What other things are there. We can say about us and well the interesting thing. The first interesting thing about the sun spot is this remark of yours that they are areas of cooler gas and the sun being at such a high temperature is entirely gaseous and for the most part very brilliant. But as we look at the disk of the sun and by the way this is something any body can do with proper care. He was in a small telescope to project the image on a card rather than looking directly as the projected image of the sun is viewed from day to day it is generally a uniform bright disk but occasionally some little dark spots will appear. On closer examination of the bigger telescope these dark spots are really quite complex. They are areas upon the sun of a very varying shades of dark and gray. And it is even possible

by special techniques to demonstrate that light comes from these dark spots. So they are not. Black in the sense a spot of paint on the wall but merely a comparatively low error areas of comparatively low radiant energy. What does anybody know I guess someone must have measured the temperature of the slot itself. Yes it can be done with the spectrum with a Very Large Telescope the image of the sun is big enough so that a sun spot. A several thousand miles across or more will be an appreciable spot on the image and big enough to cover the slit of a spectrograph and then the light which enters the spectrograph is entirely that which comes from the area of the sun spot in which case the spectrum is characteristic of something which is at a temperature of one arc. Well about 1000 degrees centigrade below the general surface of the sun. That is to say at a temperature of about 5000 degrees centigrade instead of

6000. This is evidenced by the difference in spectrum lines. Spectrum lines some of them are very sensitive to changes of temperature and when the flight area is observed at these particular spectrum lines are more pronounced or less pronounced depending on their identity. It is all clearly a matter of change of temperature and the amount is about a 1000 degrees drop centigrade. Well under these circumstances I was as you were discussing I was thinking that 5000 degrees even so it was above the melting point for instance of I guess any metal is not. Oh yes everything is still gaseous and the sun spot area one or two very refractory molecules can form Tainio oxide is one of them. That is a molecule which will form and then practically every other chemical compound we know is broken

apart by the high temperature we call that dissociation. Well there are a few spectrum lines in the light from sunspots that give evidence of this. But everything is gashes there's no question of that. And indeed if we could isolate. A large area of the sun covered by a sun spot and look at it without the brilliant background of the sun itself. It would look quite brilliant. Well that's the point. I thought I was basically thinking about was that if this is say above the melting point of tungsten in the average incandescent lamp which is used every day lighting is tungsten which is incandescent and being quite a long ways yet from melting that that is a very bright thing when you look directly at it in the older bulbs where you could see the filament directly the film was a very bright line. Yeah well you might think of an experiment that wouldn't be too hard to perform. If you have a telescope that gives a fairly large image of the sun by projection on a card. You might have a day when there is a large sun spot. I say one which made a

blot about the size of a pencil eraser on your screen and you could punch a hole about the size of a pencil lead in the screen and just let the sun spot cover that hole and then get back and look through and plenty of light coming through where the black spot is just in. Contrast with the even brighter photosphere or bright disc of the sun. Your experiment gives me an idea for another one it might be possible also without putting a whole layer to use an electric bulb and one filament kind that has a clear glass bowl that one filament lie right across the area covered by the spot and I suppose that film would look dark compared with the spot. Yes it would be much lower temperature the dogs would be only what maybe a thousand fifteen hundred degrees something like that. Yes it seems strange that it can be black and yet be right. Sounds like a paradox until you realize that it is a matter of contrast and it's not black light either. No no no.

Around the Sun spots there are frequently very interesting things known as speculate a word which means little torches. These are areas where the sun's surface appears exceedingly bright that is to say brighter than the average. And so by extending our discussion we may see that this is evidently some place where the gases are at a higher temperature or in some way are able to give us more light than the gases immediately surrounding it. It happens that these faculty are areas where the good deal of incandescent particularly calcium vapor which under certain conditions particularly when viewed against the edge of the sun not quite against the sky but near the edge of the sun give a higher percentage of visible light than immediate surroundings. And so these areas appear brilliant and are quite plainly visible. In contrast to the sun spot areas. You speak of these as being around a Sun's body area and then you mention what they would look like on the edge

of the sun is this when there is a spot at the edge of the sun that you can see this phenomenon. The sun spot may or may not be present. We ordinarily find these facts lay. In the regions of sunspots but then sometimes they appear. Alone I must say however that when we see that we're pretty likely to find spot appearing soon or have found a spot as recently there's about that place they seem to be associated. Something to do with the price turbulence in the solar atmospheres will be like that. Well definitely the sun surface being gaseous in such a high temperature is turbulent. The gases are in violent motion. Some of the most spectacular examples of that we talk about when these come through promises but even sunspots change as one watches over a period of days. The shape particularly the fact they occur in pairs and these pairs draw apart become more widely separate as we watch this all shows that we have motion of gaseous masses

and high temperature. I've heard somewhere that these are pairs of spots of which you speak are generally one I started one above the other I guess such a short term one one north or south of the other. More often than east or west of the other nurse Iris and very rarely grew as I remember it just the other way around they're all generally east and west of each other with one spot a little to the north. Of course by that north we mean away from the solar equator toward its pole for the sun does rotate and therefore have the pole of the north and the south one just like the earth. But the pairing of the sunspots is interesting because one of the evidences our spectrum gives us is that there are strong minute magnetic fields around the sun spot. This is picked up by the famous Zeeman effect is known when light coming from a strong and magnetic field is observed through the spectroscope in a certain way. Spectrum lines are no longer simple saying the lines are in pairs but maybe in groups a multiple lot of

the spectrum is rendered more complicated. This is enough. This is due to the effect of the night headache field upon me. Atoms which are radiate the light. Well the light coming from a sun spot area is definitely affected this way. So we know there are strong magnetic fields and it turns out that when you have a pair of sunspots one will be acting as a north one at it pole while its partner will be a south pole. This is the pair of spots then which you're relatively close. I mean how close are these members of a peer would show this magnetic for effect. Well of each Bach were they ten thousand miles in diameter which would not be unusual at all. They might be separated by ten twenty or thirty thousand miles. In this case we would find separated by this distance evidence of two made it feels of opposite polarity. I see then we really are quite quite close in terms of numbers though that

large. Well it's thought that they represent a. Some sort of a manifestation of motion spiral like motion of heated gases which contain electrons and as these electrons spiral they produce and they have make the field has electric current flowing in a coil of wire and that this. Motion touches the subsurface of the suddenly see in two places. And as we look down at these moving particles so to speak we're looking at them as they were in opposite directions. And as any high school student in physics knows when you have electrical currents flowing in opposite direction you get my head feels with opposite poles. I remember hearing a lecture once by Dr. Nicholson of the wells an observatory in which he discussed the effect of these magnetic fields of which you speak on a telegraphic communication here on the earth. It's very interesting things to say about that. He was talking to a group of radio amateurs that time that's reason I was there

and he remarked that sometimes the magnetic fields of the sunspots apparently are strong enough actually to cause all kinds of difficulties with the telegraphic circuits he even had some examples there are members of very interesting examples of tapes the kind that are produced in the Western Union office where you have letters on them and this is at a time when no message was being transmitted and all kinds of crazy combinations of letters and punctuation marks and so forth we would be printed on the tape. With no message actually being received at all probably the son can send out strong enough signals to actuate a teleprinter and telegraph office. Yes these are known as namesake storms which may occur with or without an immediate sun spot in evidence. We feel that it's fairly evident when there are many sunspots we are likely to have these Natick storms but that doesn't mean that when there are no spot spots particularly no large ones that we will not have

a large magnetic storm as these feels impinge upon the earth and sort of unbalance the telegraph receiver to an extent that it prints these crazy messages that you mention. I guess you could call them extraterrestrial messages even subtle when they don't make sense. Well the number of sunspots you mentioned earlier that it was erratic I believe you call that phenomenon do you mean by that that there are more sometimes less at other times. Well I wouldn't imply by the word erratic that that is actually how the sunspots behave. We may find different numbers of spots on the sun and different occasions. But if we take an accurate tally either by counting individual spots or estimating the total area of the sun that is darkened by the spots we me we find that there's a definite trend of this by the way was first figured out by an amateur astronomer in Germany not quite a hundred years ago. And one of the most famous examples of how an amateur through persistence

can discover something very important. This German Schwab by name had a small telescope more powerful than the captain spyglass. He looked at the sun or projected it through regularly at every occasion and or a period of many years. He determined that every 11 years there was a maximum of sun spot number whereas in between there was a minimum. And this followed a definite trend a cycle in other words a cycle of sunspot numbers. That sounds to me in many ways similar to the cycles which have been observed in tree rings that sort of thing. The seams of the could be a connection there. Well many people maintain that the 11 year sun spot cycle is definitely related to things which happen here on the earth such as the growth of trees the fur bearing of certain animals and any number of things even whether I think it's safe to say that these relations have not been established beyond

doubt. It is a difficult thing because there are so many influences which which could be acting. And we wonder just where the small percentage of variation due to sunspots could be important enough to imprint itself on such things as tree rings. For baring animal the weather all sorts of things. But the existence of the cycle is not to be denied. And of course any thing like the Aurora Borealis the night extortions which we know are definitely related to sunspots will also go through the 11 year cycle. By the way we are right now at the very minimum of a sunspot cycle. Probably just beginning a new cycle from the numbers of spots observed will increase until four five years from now. There will be quite a few at the end of an 11 year period. There will be very few so few as now that I have been looking at the sun off and on for several weeks and I have yet to catch a spot there may have been some I didn't have to see but there hasn't been anything very striking on the sun for quite a long time.

You mentioned Aurora. That's an interesting phenomenon. Sad to relate I've never seen an aural display. I read about them the next morning but I guess I don't stay up late enough at night or something. I saw one from on Hamilton I stepped out a door from the inside one of the domes and I thought there was a large city up there toward Mt. Diablo where there shouldn't be anything lighting up the sky. And then I realized that this was an aural glow in the north which happen to be quite strong that evening. But this was not strong enough to produce the beautiful rays and draperies such as we demonstrate in the planetarium. Doubtless though I didn't check at the time there was a good deal of sunspot activity at this particular epoch because I was strong enough to be seen from way down here in California we have to be really spectacular up in the auroral zone of the Aurora than is

produced by the sunspots and solar activity is there any more known about of just just how does this happen what what is the mechanism. Well I first must point out that we shouldn't say that they are or is caused by the sunspots what we should say is that whatever leads to a normal display of sunspots and they also lead to a spectacular display of the Aurora and there may be a common denominator. However I think it's fairly well established that the aurora is caused by streams of charged particles either electrons or protons which stream into the atmosphere of the earth and are drawn in along with a headache force lines of the earth polarity and has these impinge on the higher atmosphere about five hundred miles up. This gas glows much like a gas in an elan too. And produces the beautiful display known as the northern or the Southern Lights. From what you previously said about the composition of the atmosphere I presume it can

actually be neon it must be some other gas that does it. True it's nitrogen oxygen predominantly. But in a state of low pressure it's very difficult to reproduce in the laboratory. So I believe that this is I think a received California law signed as particularly I have been able to reproduce the auroral spectrum in laboratory tubes. It's quite a trick but it can be done. Well if one can reproduce it that's considered in science to be a pretty fair proof that you know the origin of the original phenomenon. You mentioned a few minutes ago prominences you said. Later we'll talk about promises. What are promises. The name and prominence are sometimes they're called pro-troop and indicate something which sticks up from the sun. These were first observed during eclipses of the sun when the brilliant light of the focused fear which is the brilliant disc of the Sun itself is blotted out and these brilliant reddish

streamers were seen not to be confused with the pearly corona which is much more extensive but less brilliant. These were noted and thought sometimes even to belong to the sun not to the moon rather. But it was finally proved about a hundred years ago. By spectroscopic observations taken the time of the eclipse that these were actually on the sun and it was even demonstrated by the astronomer physicist Jensen that by suitably arranging a spectroscope with a wide slit and pointing it at the slit toward the edge of the sun just off the edge of the sun that the light of a prominence could be admitted the same time the brilliant sky light. So spread out that didn't interfere with the view and lo and behold prominence could be seen without eclipses. This is a routine procedure now in observatories with more elaborate devices and prominences can be observed and photographed at any time. There are

spectacular things in many cases reaching heights of hundreds of thousands of miles each remaining in their unchanging for hours or at a moments notice just shooting up. Seemingly leaving for outer space or collapsing and falling into the sun at a rate to go up to hundreds of miles per second. Just more evidence of the tremendous turbulent nature of the gaseous atmosphere of the sun. Your statement about this reminds me of something that I was going to mention going to ask you about when we were discussing observatories. We didn't mention as far as I recollect the McMahons Hurlburt observatory Isn't that the place where they make a practice of making motion pictures daily or any time the weather permits. Oh prominences Yes they have equipment which runs continuously whenever the sun is out and observe and they record the moment to moment changes the films or run off every minute

or so. That is one frame a minute and then when these are run off at standard. Move motion picture speed the changes in the prominences are very evident and quite spectacular to watch and make beautiful pictures sometimes by spacing the photographs closer or more quickly changing effects can be picked up such as the tiny spicules spicules or just baby prominences instead of being hundreds of thousands or tens of thousands of miles high and they only be five hundred or a thousand miles and they look like well to me like a stubble. You know waving fields of grain and his sort of flickering and going back and forth they shoot up and fall back evidently little jets of gas jets by the way is a good term here. It was jets of gas which would leap up short ways and fall back. And this is from the surface of the sun or from parts of the prominence from the surface of the sun right above the so-called focus

fear. It's very interesting that recently the WHO study these things that worked out the mechanism by which the spec you speak you was could be maintained. And it seems that it's by shock waves in the turbulent gases shock waves are part of what goes on and they have airplanes going through the sonic barrier and someone has even gone so far to say that if you could be up on the sun around the spicules it would be the noisiest place on in creation. I mean they they actually are proceeding out of the sun not at speed such that the they set the solar atmosphere so to speak in a vibration vibration just the shock waves as when some object goes rapidly through the atmosphere of the earth. The prominences are a beautiful thing to watch. Some people call them flames the appearance is striking like a flame but we must realize that they cannot be due to any combustion.

And many people don't realize it but the sun is too hot to burn. Remember we said there were no compounds possible in general and of course compounds like chemistry of compound is necessary for burning. That is impossible on the sun. I see. Well do the other any other let's put it that way other any other things such as these prominences and spicules which might have let's say effects on the earth it's always interesting to know about things that are going to affect us. Well yes the sun is the most important astronomical body you might say it's as important as the earth because the Earth wouldn't do with a great deal if it weren't for the good. If it were not for the sun. Well the flares which appear on the surface of the sun are very important and they are areas where the amount of radiant energy increases tremendously and that may happen in a moment or two. Whatever it is that creates the energy of the sun it would seem to burst through at this point and at a

mall in a moment's notice. A great deal of radiant energy will be released particularly in the short wavelengths in the ultraviolet. This sends out a radiation which when falling upon the upper atmosphere of the earth completely cancels out the reflecting layers that are responsible for short wave transmission. These so-called heavy side layer is rendered transparent to radio waves short waves anyway. And so transmission of signals which depend upon reflecting from the upper atmosphere are just impossible. And during the last war berth both sides of the conflict had solar observatory set up so that the currents of flares could be accounted for and could be anticipated certain radio channels would be of no use for military communication. These fires are still quite something to study we of course or study them all the time and in many ways it seems to me and they are the most spectacular of solar phenomena has been said