Lectures on Stellar StatisticsCharlier, C. V. L. (Carl Vilhelm Ludwig)
Science
Lectures on Stellar Statistics
Charlier, C. V. L. (Carl Vilhelm Ludwig)
Astronomy; Milky Way; Stars
The next brightest star is _Canopus_ or α Carinæ at the south sky. If we
might place absolute confidence in the value of _M_ (= -8.2) in the 12th
column this star would be, in reality, a much more imposing apparition
than Sirius itself. Remembering that the apparent magnitude of the moon,
according to §6, amounts to -11.6, we should find that Canopus, if
placed at a distance from us equal to that of Sirius (_r_ = 0.5 sir.),
would shine with a lustre equal to no less than a quarter of that of the
moon. It is not altogether astonishing that a fanciful astronomer should
have thought Canopus to be actually the central star in the whole
stellar system. We find, however, from column 8 that its supposed
distance is not less that 30 sir. We have already pointed out that
distances greater than 4 sir., when computed from annual parallaxes,
must generally be considered as rather uncertain. As the value of _M_
is intimately dependent on that of _r_ we must consider speculations
based on this value to be very vague. Another reason for a doubt about a
great value for the real luminosity of this star is found from its type
of spectrum which, according to the last column, is F0, a type which, as
will be seen, is seldom found among giant stars. A better support for a
large distance could on the other hand be found from the small proper
motion of this star. Sirius and Canopus are the only stars in the sky
having a negative value of the apparent visual magnitude.
Space will not permit us to go through this list star for star. We may
be satisfied with some general remarks.
In the fourth column is the galactic square. We call to mind that all
these squares have the same area, and that there is therefore the same
probability _a priori_ of finding a star in one of the squares as in
another. The squares GC and GD lie along the galactic equator (the Milky
Way). We find now from column 4 that of the 20 stars here considered
there are no less than 15 in the galactic equator squares and only 5
outside, instead of 10 in the galactic squares and 10 outside, as would
have been expected. The number of objects is, indeed, too small to allow
us to draw any cosmological conclusions from this distribution, but we
shall find in the following many similar instances regarding objects
that are principally accumulated along the Milky Way and are scanty at
the galactic poles. We shall find that in these cases we may _generally_
conclude from such a partition that we then have to do with objects
_situated far from the sun_, while objects that are uniformly
distributed on the sky lie relatively near us. It is easy to understand
that this conclusion is a consequence of the supposition, confirmed by
all star counts, that the stellar system extends much farther into space
along the Milky Way than in the direction of its poles.
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