American citizen. [volume] (Canton, Miss.) 1864-1890, 1881-07-09
Something About the Comet.

| so suddenly 4 couple OF days ago was
watched and its position measured yester-
| day morning through the big telescope al
| the Dearborn Observatory. The length o!
the comet and tail measured almost precise
ly eight and Il half degrees, with ley signs
of streamer light extending little fur her
but not forming definite tail beyond the
| limit named. Some of the published esti-
mates of length, made by the parties who
| first saw the comet, We're much greater than
this. 1t appears probable that the tail was
really longer on Wednesday morning than
yesterday; as it is SO described by gentle
man who saw it on both days. At twenty
four minutes past three O'Clock the declina-
ton was forty-six degrees forty eight min
utes north, and the right ascension five
hours and thirty-six minutes, within a few
seconds.
The comet is travelling Mt the rate Of abou;
five degrees northward, 215 minutes of time
eastward, per day. The angular diameter
IT the nucleus was Ga seconds of arc, and
The distance from its center to the apparent
top of the envelope was &c seconds of arc.
Day before yesterday it was mere matter
of guess that this newly discovered comet
was Identical with the comet of 1872. which
was discovered by Pons in July, passed its
perihclion in September, aud was computed
by Encke to have n period of seventy and
seven-tenths years, which would bring it
around again in the early part OF 1888. 1t is
4 well known fact, however, that the meas
ures Of position of a comet, moving in a
very elongated orbit, can scarcely be
depended upon to give a result much nearer
than this, especially if the perturbing attrac-
tons OF the planets # the solar system are
not taken into the account. The comet of
1872, for instance, has swung out into space
at distance from the sun fifteen times
greater than that OF the earth, which carried
it considerably beyond the orbit of Saturn,
and the attracting power of the giant masses
of the solar system, to say nothing of the
hundreds of asteroids which have been dis
covered since Encke made his calculation.
are quite sufficient 10 cause such difference
in the result, if the comet passed near some
Of them.
Making due allowance for this, the motion
Of the comet, as so far observed, is partly
reconcilable with that of the comet of 1872.
1t is travelling in, approximately, the same
plane, but the position of the point Of peri
helion passage in the computed orbit does
not appear TO agree with that of the pres
ent comet. The measures taken yester-
day have been collated by the Tribune as
ing as approximate statements of magni-
tude-in terms with which the average read
CT is more familiar than with degrees and
minutes:
The distance Of the comet from the earth
yesterday morning WAS $4,000, 900 miles; the
diameter of the nucleus, 1000 miles; the
shortest diameter Of the comet, measured
through the nucleus, 10000 miles; and the
length of the tail 4 200 600 miles
The comet would appear to have already
passed (nearly) between the earth and the
sun; and the shortening of the tail, above
referred to, might be supposed to indicate
that it has passed its perihelion some days
ago. The latter, however, does not rest on
sufficient data yet. 1t is well known that
ut least three observations, at moderate in
teryals Of time, must be made of comet
before the elements of its orbit can be de-
termined by its computers. Hence other
observations, besides those made yesterday,
Will be required to establish the leading
facts OF the comets movements. The re-
quired measures will be made at the Dear
born Observatory and at numerous other
places weather permitting; and the comet
is rapidly moving into a more favorable part
of the heavens for measuring than that in
which it has hitherto been seen in
the United States. As above noted the
comet is rapidly moving northward. The
degrees of yesterdays motion carried it so
far north that it was above the horizon dur
ing the whole of last night, instead of being
about four hours below, as on the previous
night. 1t will be above the horizon the
whole of Tomorrow night, passing the low
est point due north about twenty minutes
past eleven o'clock, and will be visible, with
a clear sky, from dark till twenty minutes
past eleven to the west of north, and from
twenty minutes past eleven till daylight to
the east Of north. just how long it will
continue visible cannot at present be told,
but it will undoubtedly be a brilliant object
in the evening sky for several days. and pos
sibly weeks, hepee. The line of reasoning
adopted in regard to its present distance
leads, however, to the conclusion that it is
decreasing in brilliancy.
1t may be interesting to know that the
length of the tail yesterday morning was
four times the greatest observed length Of
Tail carried by the comet of 1872. That,
however, is no proof that the two are not
Identical, as the apparent length Of tail de-
Ponds upon the distance from the sun when
seen, and also, to a very large extent, upon
is distance at the same time from the OBJ
server, who watches it from the surface of
he ever-moving earth.-Chicago Tribune,
Iu,s %.