The angle he makes with our orbit diameter is one-fourth of a second; so that he is about 80,000,000,000,000 miles.
Thank you, dear father, for these terrible long figures.
Their great distance may give us a good guess of their great size.
I know the size of the sun to be half-a-degree in the heavens, at a distance of ninety-five millions of miles, and yet it is really eight hundred and eighty-six thousand miles diameter, I have been told. When, then, a star is millions of millions of miles away, I am sure it must be a big one to be seen at all.
It is so. If the sun were thrust back as far as the star a Centaur, it is calculated that it would not shine with more than one-third of the light that star now gives us; it must, therefore, be not more than one-third its size.
But you said Sirius was four times farther off than the Centaur, father.
Yes; and it gives four times as much light. It is, then, probably four times as large. It must be, therefore, many times larger than the sun.
I am sure it ought to have more planets turning round it than the sun has, or else have them much larger in size.”