It was upon a lovely evening, when off the coast of South America,
ready to slip across by the side-help of the South-east Trades to the
Cape of Good Hope, that Mr. Marple found his son at his old post.
“Now then,” said he, “my star-gazing boy, are you quite sure that
none of them have run away since last night?
I am not sure of that, father; for ever since you proved that the Fixed
stars were not fixed, I think I might some day find a bright friend
gone on a visit to another universe somewhere; perhaps, getting into
such agreeable society as to have no wish to come back again to our
visible universe; or, maybe, to pop back again in his place.
It so happens, James, that what you have imagined, really takes place.
Some stars do really disappear, to return, or not; and others, wholly
strangers to us, come within observation.
That is the queerest thing you have told me yet. What droll fellows
the stars are, after all! How they do wriggle about, polkaing here,
doubling there, and fielding about like boys at cricket. I shall never
be surprised at any funny trick you ascribe to them.
To begin with the _Variable stars_, of which there are known about one
hundred. There is Mira, which is invisible five months in the year. It
goes and comes again.
Where could it have got to?
Some think it revolving round a dark object; and, of course, becoming
invisible when on the other side from us. One passes through three
magnitudes in one month.
But I must give you the history of such a curious star in the Whale.
For two weeks you might see it a noble star of the second magnitude.
It gradually dims, till it goes fairly out of sight in three months.
For five weeks you see nothing of it. It then reappears. Altogether it
seems to have a revolution of 322 days; and is, therefore, one of the
_Periodical_ stars.