When we view the outburst of that remote sun in this way the thoughts suggested are not altogether satisfactory. That sun shows far too much resemblance to our own, and behaved, so far as can be judged, far too much as our own sun would behave if roused to many times its present degree of heat and splendour. When we hear of a railway accident it is a matter of special interest to us (if we travel much) to learn whether the conditions under which the accident took place resembled those under which the trains proceed by which we chiefly travel. When an express train suffers in such a way as to show some special danger arising from great velocity, we find ourselves to some degree concerned personally in the investigation which follows, if we travel generally by quick trains. If a bridge breaks down, and we have often to traverse bridges in railway journeying, we are similarly concerned, especially if any of the bridges we have to cross resemble in structure the one which has given way. So also of many other special forms of danger in railway travelling. Now, on the same principle, we cannot but regard with considerable interest the circumstance that, apparently, a catastrophe has taken place in the star in Cygnus, which has not only affected a sun resembling our own very closely in constitution, but has produced effects very closely corresponding to those which would affect our own sun if, through any cause, he were excited to many times his present degree of heat.
Let us pause a little to reflect upon the effects which would follow a great increase of the sun's lustre. A change in our own sun, such as affected the star in Cygnus, or that other star in the Northern Crown, would unquestionably destroy every living creature on the face of this earth; nor could any even escape which may exist on the other planets of the solar system. The star in the Northern Crown shone out with more than 800 times its former lustre: the star in Cygnus with from 500 to many thousand times its former lustre, according as we take the highest possible estimate of its brightness before the catastrophe, or consider that it _may_ have been very much fainter. Now, if our sun were to increase tenfold in brightness, all the higher forms of animal life and nearly all vegetable life would inevitably be destroyed on this earth. A few stubborn animalcules might survive, and, possibly, a few of the lowest forms of vegetation, but naught else. If the sun increased a hundredfold in lustre his heat would doubtless sterilise the whole earth. The same would happen in other planets. The heat falling on the remotest members of the solar system would not, indeed, be excessive according to our conceptions. But if we regard Neptune, Uranus, Saturn, and Jupiter as the abode of life (which, for my own part, I consider altogether improbable), we cannot but suppose the orders of living creatures in each of these planets to be well fitted to exist under the conditions subsisting around them. If this is so--as who can for a moment doubt?--a sudden enormous increase in the sun's heat, though not making the supply received by those planets much greater than, or even equal to, the supply which we receive from the sun, would prove as fatal to living creatures there as to living creatures on our earth.