Evening star., 1896-10-31

as Mira, the Wonderful" one Of the most
freakish Of the variable stars-particularly
interesting because Of the great range of
its variability-is now on the point of COM
ing into visibility to the naked eye, and
will probably reach its maximum of bril-
lancy some time next month. 1t is in a
particularly good position for observation.
and no who is interested in celestial
phenomena should miss this opportunity of
forming the stars acquaintance and noting
it's eccentric:ties.
The popularity of Mira is this: Ordinarily
1t is invisible to the naked eye, being.
when at it's faintest, Of between the ninth
and tenth magnitude. Having remained at
this point of lowest brilliancy for some
weeks, it begins slowly to brighten, and
after awhile 1t becomes visible to the naked
eye. 1t continues to brighten for a month
or six weeks longer, when it attains a max
imum Of brilliancy, which is usually that
Of a star of about the third magnitude. In
this condition 1t remains, sometimes f1uc-
tuating in brightness for fortnight or so.
and then begins to lose its luster, and in
about three months 1t Is again beyond the
reach of the naked eye.
Mira runs the cycle of its change in an
average period of about eleven months,
though there Is a considerable irregularity
in its period, we'll as In it's brilliancy,
when at its brightest Its last maximum
occurred some time in January last. Ow-
ing. however. to the prevalence of cloudy
weather during that and the preceding
month, observers were not able to fix upon
the precise date of the occurrence nor to
determine very exactly the stars greatest
brilltancy. 1t appears to have fallen short
OF the third magnitude
A Shoal of Meteors.
The cause of the singular department of
this and similar variable stars is among
ha r,bt btoh
ing to unriddle. Upon Mr.. Lockyer's me
teoritic theory" Mira is not. strictly speak
ing, 'star'-that Is, a sun. It is simply
condensins shoal Of meteors, its light be-
ing due to heat engendered by the collisions
of these meteors. which are assumed to be
In motion among then selves. owing to
their mutual attraction for one another
There are here, according to Mr.. Lockyer
two such meteor shoals, circling about
each other in orbits of such eccentricity
that while ordinarily the two masses of
meteors do not interfere with one another
yet when they are nearest together one of
item grazes or passes partially through
the other. AS consequence the collisions
become more numerous and more violent.
and we see the star" increase in brill
liancy. The spectroscope shows that the
stars increase in splendor is due mainly, If
not wholly, to an Outburst of glowing
gases fact which is quite in harmony
with Mr.. Lockyer's theory. Indeed this
theory was based originally upon expert
ments made with the spectroscope When
shining only family the star is decidedly
red; but as 1t brightens it loses it's redness,
and Its spectrum shows bright lines, indie
ative Of luminous gases. among which is
the ever-present hydrogen.
Mira Will be, tomorrow at Q pm in mid
heavens IN the southeast To find it-or its
position. for 1t is not now visible-frst find
Aenkar, the second magnitude star in the
snout of Cetus. This star forms, with the
fieiades and the pair Of stars in the head
a fYfo v,rr1o
10 the right Of Menkar Is group of three
stars. as shown on the planisphere, The
middle one Of these is Gamma Ceti, of the
tn,rd tnmri magnltude: The iowermost. Of the
Delta Is almost exactly midway between
Menkar and Mira. With an opera glass. a
small triangle of seventh-magnitude stars
may be seen In the spot here Indicated
Mira VIII make Its appearance at the CEN
ter OF this triangle. Keep a watch upon it.
In Streak of Splendor.
Besides planets and comets there are
circling round the sum- and therefore form
ing part Of the solar system, innumera-
Die minute particles Of matter. too small TO
! be seen under ordinary circumstances with
even the most powerful telescope bu. some
OF which occasionally become momentarilv
visible as the familiar meteor or shooting
star. Ihe appearance of a meteor is due
TO an Academia fatal accident for the
meteor. In an unlucky moment it has
tried to cross the earth's orbit and Eas
been struck by the earth. The collision
Is 1rlghtful one. for the earth Is travel
Ing In Its orbit at the rate of eighteen rsiiles
second, and the meteor may be moving
with an equally great rapidity, possibly in
contrary direction. Entering the earth's
atmosphere with speed Of fifty or one
hundred times that of rifle ball. 1t quick
ly becomes heated to redness to whiteness,
and usually within a second OF time it has
perished in a streak of splendor
TheSe meteOrS are associated into CON-
arate systems, millions of them perform
| Ing their revolution round the sun in the
| same orbit and forming what Is com
monty spoken of as a meteoric stream"
One of the best known of these meteor
| systems Is that Of which the orbit is an
nually crossed by the earth between the
18th and 18th Of November This great
body Of meteors." says Professor G. john
| stone Stoney, in an article recently pub
lished in Monthly Notices, "traverses an
immense oval orbit which near Its outer
| most limit crosses the path of the planet
/ ffa