Evening star., 1901-11-09
THE LEONID SWARM
A Great Shower of Shooting Stars
Due.
LAST ONE WAS "a YEARS AGO
Earth's Orbit Crosses Meteoric Path
Thrice Century.
NJ s 'TNH EnIS IT III ENn
WATCH FOR THE FIREWORKS

Written for The Evening Star
Will the great Leonid swarm, expected
| last year and the year before come this
year? For two years past all devotees of
astronomy, professional and amateur, have
had their hopes followed by disappoint-
ment, as they watched during the nights
OF November IL, IA and Is for the coming
or the most famous shower of shooting
stars known to the science. VIII this year
witness another and a final disappo!n.-
ment? Certain astronomers believe not;
they think that the Leonids will appear
this month in all their original splendor
| All observing people have seen shooting
| stars, but not till within a few decades
was it known that every shooting star
toi5oWed sen .he laws that govern all heavenly
| bodies, pursuing each its appointed path
so that If We had complete knowledge of
! them the flash of each one or, at least of
every considerable group of them, might
De as certainly predicted the appearance
| of the planets.
OF a.. the shooting stars the Leonids, as
! tne November swarm is called, are by all
| odds the most striking to the eve the most
| numerous, have filed the largest place in
history and, it is believed, offer the as
| tronomer the most frutIul field for re-
ssarch. Few OF the swarm were seen on
November IA, 1897. The swarm was then
| looked for on the night of November IA
| 1888, and few days before and after and
at that time about 500 We're noted.. No
|
awaited their coming, armed with the lat
est Photographic weapons of our photo
= graphic age From 100 to 200 We're re-
corded. Last year again though win
diminished hope. the watchers of the sky
made ready, but again there We're no sub
stantial results. Something over hun
sn, ared Were noted altogether in northern
ATTITUDES, principally at Yale and Har-
! Vard Prof W. H. Pickering of the Har2
Varo observatory, favored with a clear
SKY at the station which he was then
Il a N inc To-,
over hundred on each of the two nights
| on which he observed them But this was
nothing to the glorious records Of the
| s, swarm IN the past In the ninth century
! the Arabs recorded its appearance in their
| annals as rain of stars" The Chinese
nave 1t IN their astronomical records as
early as BIB, and again in 1902, the last
time by thousands" with two of the me-
teors as large as quart measure. From
that time to this they have been noted
with far regularity every thirty-three
| there-and always in terms that hesnoks
sight OF splendor and sublimity.
The Last Display.
| Inc last hrst-class shower in this coun-
| try was on November IA, 1893, though on
| November 13, 1882, there was a consider
| aple display in Europe. On November a.
| Ieoo, they appeared again, the largest dis
play coming in November. 1867, however,
| when the astronomers and newspapers OF
tne tline write of them as wonderful ano
glorious phenomenon. But the year for
! tnelr next recurrence has been yarfousfy
| nxed by astronomers, depending on the
year assigned as the last of a small eroup
! oL years. referring to the last appearance
1900 mas been chosen by some a starting
| point; and period of thirty-three wears
| between the swarms would bring them
| back in 1899. The year 1867 appears. how.
! ever, from contemporary accounts to have
| produced the best display. A thirty-three-
! would hrip
| back in 1900. But on the other hand it has
| been shown that the period of the swarm
nas peeh iengthenlng, and must now be
close to thirty-four years-a calculation
winch would assign the present month a.
the proper time of their temperance
| Prof. w. II. Pickering of the Harvari
observatory claims that the estimate OF
thlrty-four years, reckoning from 1867 is
sustained by the best data His present
| statement is as follows:
| Computing from 902, the first certain
date, and onitting for convenience all mid.
century appearances, they had a period OF
| thfrty-three and one-quarter years appear
! ing in 1902, 11O1, 1902. 1902 1902 1909 aud
l6o2 A change seems to have come in the
orplt at that 3uncture, and, instead of one
hundred years later they appeared not
every thlrty-three years, but every thirty
| four Years.
| Beginning from IS33," Prof. Pickering
| continues, the last year of an unuues
! toned maximum, We get 1867 as the next
appearance in considerable numbers and
the accounts of the last appearance of the
swarm assign 1867 the last year though
| 1866 had a considerable display Continu.
| ing the computation, then, 1901 would be
| the end of the next thirty-four-year period.
Shape of the Swarm.
"A hope of seeing the shower supposing
the perturbation is as outlined above lies
in the probable shape of the swarm. The
meteors are strewed along the orbit fol
| millions of miles, long enough at least so
that the earth may make two or three rev.
olutlons around it's own orbit before get
ting clear OF the swarm. 1t is not supposed
that the meteors, which are small dark
DodleS, are distributed in space in a cylin.
der-shaped figure, but more like a strap
ana this strap is wayy or Zigzag in outline
each wave being the record of a perturba.
tlon due to the passing of one or more OF
the planets near the swarm. The some
what remote chance of the earth intercept.
ing crest of one of these waves is to be
regarded as one of the hopes of the as.
tronomer. 4
THE Leonid swarm is nevertheless Well
worth watching for, even If not as numcr-
Gus as on its former appearances. For one
thing, they are among the brightest OF
meteors and offer the best probable chance
of securing spectrum, leading to a knowI !
edge of their constitution. They are NOV.
ing in a contrary direction to the motion of
the earth in its orbit and when intercept.
ed by our atmosphere, their velocity is the |
sum of their own and the earth's. They
are lHuS TedOly 1uentlne0, being quick. |
bright flashes across the sky, usually with |
blush light, but sometimes yellow This
brightness of the light is what the spe-.
troscopist would desire in his researches
though it is obtained at the expense of the |
length of exposure"
A Long Stretch. i
The great eclipse of the Leonid orbit |
has a long diameter-some 100000 600 |
miles-and the swarm has completed this
enormous circuit 1fty-two times. next
month. If it occurs. being it's ffty-third !
appearance. The best considered theory of |
the appearance of the Leonids as shooting
stars in our terrestrial atmosphere supposes
that the orbit of the earth crosses the orbit |
OF the meteors and that once in thirty |
three-or thrty-four-years the earth runs !
into the swarm-that is, into the place of |
their greatest frequency-taking three or |
four days to cross it. The point on the |
earth's atmosphere where the swarm is In
tercepted Is in line with point in the con- !
stellation Leonis (or the Lion), whence the
name of Leonids. The determination of |
this radial point is an important consider