The Locomotive - Lighthouse Survival Blog

1901.] THE LOCOMOTIVE. Igg
when Professor Barnard examined it he perceived that it was really ' a small, bright
nebula, with a tenth magnitude nucleus.' The brighter part of the nebula was 3" in
diameter, and outside of this was a fainter nebulous extension that was perhaps 30" in
diameter.
"The phenomena so far described are as follows: On December 8, 1891, no star as
bright as the ninth magnitude was visible in this part of the heavens. On December
10th a star of the fifth magnitude, distinctly visible to the naked eye, was there. From
this time until about the 1st of March, 1892, the newcomer fluctuated greatly in bright-
ness, but from the 1st of March onward it faded away with considerable regularity until,
when it was last seen, on April 26th, it was, perhaps, of the sixteenth magnitude. It
was then supposed to have permanently disappeared; but on August 17th it was again
seen, far brighter than it was on April 26th, and it was found to consist of a tenth mag-
nitude star, surrounded by a nebulous envelope. This in itself is a sufficiently remark-
able cycle of changes, but let us see what the spectroscope had to tell us. When the
star was first seen it had a complicated spectrum, composed of bright lines, on the violet
side of which were dark lines looking like shadows of the bright ones. This was
interpreted as meaning that the star really consisted of two bodies of similar chemical
composition, one of which was approaching us and the other receding from us.
Measures of the displacement of the lines showed that the body giving the dark lines
was approaching us at the enormous speed of 300 miles per second, while the one giving
the bright lines was receding at the rate of 420 miles per second ! * These velocities
were maintained for at least a month, during which time the distance between the two
bodies must have increased by an amount equal, at least, to twenty times the earth's
distance from the sun.
" After the reappearance of the star in August, its spectrum was found to be entirely
changed. It had taken on an appearance characteristic of the nebulae ; and a couple of
days later Mr. Barnard saw it nebulous, as explained above. Professor Campbell of the
Lick Observatory has also found indications of tremendous changes in the velocities of
the two bodies composing the star; but this needs verification before we can accept it as
a fact.
"Astronomers have proposed various theories to account for the remarkable outburst
of light from the new star. The first explanation that occurs to one is that two com-
paratively dark stars, coursing along through space, have come into collision with one
another, and that so much heat has been developed by the consequent slackening in
speed that the bodies have been heated up to strong incandescence. It is also held by
some that the phenomenon was produced by the crashing together of two vast clouds of
meteoric stones. (This supposition is in accordance with Lockyer's famous ' meteoritic
hypothesis. 1
) Others point out that it is not necessary to suppose that an actual collision
took place, but that the two stars approached each other so closely that enormous tides
were raised in both of them, the resulting friction of these tides being the cause of the
heat that was generated. This theory seems fanciful, but it is undoubtedly tenable.
The strongest objection to it is the suddenness with which the star burst forth.
" Whatever theory we adopt concerning the cause of the sudden brilliance of the
star, we have to face a far more difficult question when we consider the reasons for its
fading away so quickly. Those of us who know how long it takes a large ingot of metal
to cool will be slow to believe that a body at least comparable in size and heat with the
sun could possibly cool down in a few months to the extent to which this new star has
cooled."
*For an account of the principles on which this conclusion is based, see The Locomotive for June, 1890.