The San Francisco call., 1906-06-24
STARS THAT N1YSTFY WORLD OF SCIENCE

were stationary. and this is shown in
the spectroscope by a crowding of the
speetroscopic lines toward the violet
end of the spectrum, which is composed
of the smaller light waves, while re-
ceding star would be Indicated by a
crowding of the lines toward the red
end of the spectrum.
In the case of the star referred TO II
was found that there are two distinct
sets of lines which alternately move
toward opposite ends of the spectrum.
This clearly shows that the star is
composed of two bodies which are al
ternately approaching toward and re-
ceding from US. or, in other words, that
they are revolving about each other.
The exact rate of their motion can be
figured out mathematically by the ex-
tent to which the lines are crowded out
of their normal positions.
In some cases one of the twin stars
is a dark one, and then the light of
the bright star will remain constant
except at regular intervals when the
dark star passes before it and obscures
it's light. The entire light is not cut
off, because the dark star may be either
smaller than the bright one or 1t may
pass a little below or above it. Such
variable stars it is difficult TO discover,
because the duration of the eclipse is
usually only a little over an hour. and
the chances of an observation during
the time of this eclipse are exceed
ingly small.
Variable stars of the type of Mira
are still almost as much of a problem
as before the age of telescopes. Their
fluctuations are not regular enough in
degree or in time to be caused by twin
stars. The heavenly bodies which move
in orbits can always be depended upon
to keep accurate time. 1t is possible
that the occasional blaze of light is
due to a gigantic internal eruption.
There are indications which appear to
confirm this theory, but it seems hard
to believe that disturbance of such
an enormous proportion as would be
required TO produce the extreme va
riations of light could occur within
the star itself. Nor are stars of this
type exceptional Fully three-quarters
of the known stars belong to the Mira
class. 1t is in the study of such stars
as these that laymen can best assist
astronomers by making records of their
variations
BY far the most remarkable variable
stars are those which suddenly appear
where no star was ever before seen.
endure for a brief period. and then
vanish apparently forever. These are
more properly called temporary stars.
In November. 1872. new star of the
first magnitude appeared in the Milky
Way. 1t grew brighter until it out
shone every other star in the heavens
and was visible even in daytime. Then
it began to fade and was lost TO view.
The event caused great excitement at
the time, giving rise to the supersti-
tion that this was the star of Bethle-
hem returned to herald the second COM
ing of Christ. The next temporary star
was discovered about thirty years lat
er in different part of the heavens.
This star also grew very brilliant for
a time, though it did not quite reach
the brilliance of the previous one. After
about a year it faded completely from
sight. Temporary stars of such remark
able brilliancy are exceedingly rare,
but telescope temporary stars are occa-
sionally found by means of photogra-
ply.
About five years ago a star was dis
covered which grew RAPIDLY brighter.
and in four days it's light increased
10000 times, making it the third