The Children's Book of Stars

ave not examined in detail this marvellous furnace that nourishes all the life on our planet and burns on with undiminished splendour from year to year, without thought or effor

e is now, and there would be as great a distance between the moon and the shell of the sun as there is between the moon and the earth. This gives us a little idea of the size of the sun. Again, if we go back to that solar system in which we represented the planets by various objects from a pea to a football, and set a lamp in the centre to do duty for the sun, what size do you suppose that lamp would have to be really to represent the sun in proportion to the planets? Well, if our greengage plum which did duty for the earth were about three-quarters of an inch in diameter we should want a lamp with a flame as tall as the tallest man you know, and even then it would not give

ve on earth could even compare with it. Of his radiating beams extending in all directions few indeed fall on our little plum, but those that do are the source of all life, whether animal or vegetable. If the sun's rays were cut off from us, we should die at once. Even the coal we use to keep us warm is but sun's heat stored up ages ago, when the luxuriant tropical vegetation sprang up in the warmth and then fell down and was buried in the earth. At night we are still enjoying the benefit of the sun's rays-that is, of those which are r

much larger in their time; but we have no record of this; on the contrary, all records of the sun even to five thousand years ago show that he was much the same as at present. It is evident that we must search elsewhere for an explanation. It has been suggested that his furnace is supplied by the number of meteors that fall into him. Meteors are small bodies of the same materials as the planets, and may be likened to the dust of the solar system. It is not difficult to calculate the amount of matter he would require on this assumption to keep him going, and the amount required is so great as to make it practically impossible that this is the sou

und without some heat being generated. Now, when this great nebula first began its remarkable career, by the action of gravity all the particles in it were drawn toward the centre; little by little they fell in, and the nebula became smaller. We are not now concerned with the origin of the planets-we leave that aside; we are only contemplating the part of the nebula which remained to become the sun. Now these particles being drawn inward each generated some heat, so as the nebula contracted its temperature rose. Throughout the ages, over the space of millions and millions of miles, it contracted and grew hotter. It still remained gaseous, but at last it got to an immense temperature, and is the sun as we know it. What then keeps it shining? It is still contracting, but slowly, so slowly that it is quite imperceptible to our finest instruments. It has been calculated that if it contracts two hundred and fifty feet in diameter in a year, the energy thus gained and turned into heat is quite sufficient to account for its whole yearly output. This is indeed marvellous. In comparison with the sun's size two hundred and fifty feet is nothing. It would take nine thousand years at this rate before any diminution could be noticed by our finest instrum

mth of our planets is assured for untold ages. There is no need to fear that the sun wil

be followed by an astronomer as it passes all across the sun, disappears at the edge, and after a lapse of time comes back again round the other edge. This first showed men that the sun, like all the planets, rotated on his axis, and gave them the means of finding out how long he took in doing so. But the spots showed a most surprising result, for they took slightly different times in making their journey round the sun, times which differed according to their position. For instance, a spot near the equator of the sun took twenty-five days to make the circuit, while one higher up or lower down took twenty-six days, and one further out twenty-seven; so that if these spots are, as certainly believed, actually on the surface, the conclusion is that the sun does not rotate all in one piece, but that some parts go faster than others. No one can really explain how this could be, but it is certainly more easily understood in the case of a body of gas than of a solid body

tory, Greenwi

change of appearance as they pass over the face of the sun toward the edge; fo

's own brilliance is our greatest hindrance in observing him, his rays are so dazzling that they light up our own atmosphere, which prevents us seeing the edges. Now, during a total eclipse, when nearly all t

IN COMPARISON WITH THE FLAM

adually blotting out more and more, eager telescopes follow it; at last it covers up the whole sun, and then a marvellous spectacle appears, for all round the edges of the black moon are seen glorious red streamers and arches and filaments of marvellous shapes, continually changing. These are thrown against a background of pale green light that surrounds the black moon and the hidden sun. In early days astronomers thought these wonderf

but a tiny ball, and this is going on day and night without cessation. Look at the picture where the artist has made a little black ball to represent the earth as she would appear if she could be seen in the midst of the flames shooting out from the sun. Do not make a mistake and think the earth really could be in this position; she is only shown there so that you may see how tiny she is in comparison with the sun. All the time you ha

ents, which seem to shoot out in all directions; generally these are not much larger than the apparent width of the sun, but sometimes they extend much further. The puzzle is, this corona cannot be an atmosphere in any way resembling that of our earth; for the gravitational force of the sun, owing to its enormous size, is so great that it would mak