Evening star. [volume] (Washington, D.C.) 1854-1972, 1889-02-23
CELESTIAL VISITORS.

stoIk anu Inc goose.
| NJ. E. W. SHERWOOD.
| CELESTIAL VISITORS.
Where Comets Come From and How
| They are Found.
A STAR reporter asked Mr.. Geo. A. Hill, who
| is now engaged at the Naval observatory
searching for comets, to explain how these
strange celestial visitors are found.
Il imagine" replied Mr.. Hill, that readers
! of The STAR would be very anxious to learn all
about this subject should bright comet, with
tail 80 or 40 degrees long. suddenly appear in
the heavens, but as that phenomenon is quite
rare the three comets now visible by aid of the
telescope would not excite much interest ON
the part of the casual observer.
"Comets, whether faint OF bright. are. how
ever, interesting objects for study. and we will
continue to observe these until they pass out
or slght. To my mind comet is the most
wonderful of all celestial bodies Not in the
sense OF Its size or importance in our solar sys-
tenn, but because Of the mystery that surrounds
IL. Dld you ever stop to consider that 80 per
cent OF the comets observed each year have
never before been seen by mortal ewes? Where
do they come from? do not know.
TRAVELLING THROUGH SPACE.
"The moon, planets and stars shine tonight
with the same splendor, and look down upon
us just as they did when the builders of the
pyramids were carving out the stone that was
used IN building that monument, 5000 years
ago. But venture to say, that the two little
comets now sweeping through our skies, were
at that time passing through a portion OF
stellar space of which we have not the sliqbtest
conception. They have been all these wears
gradually drawing nearer to the sum- and in
the year 1889 we are permitted to observe them
for time and they are gone forever In its
journey through space a comet moves in one
OF three curves, an ellipse, q parabola or a
hyperbola. II the comet moves in an ellipti-
cal orbit 1t will return again to the SUM- If i'm
an orbit of a parabolic nature the comet rusbes
toward and around the sun, and then passes off
Into space never again to be observed by u.s.
Two of the comets now in view are moving in a
parabolic orbit, and they will soon be lost to
our sight The third, Faye's, named after its
diseoverer, is moving in an elliptcai orbit
which 1t takes about seven and half years to
complete. This comet has just approached the
sun for the fifth time since it was discovered.
SEARCHING FOR COMETS.
I'm searching for these erraIic objects"
said Mr.. Hill II use telescope of peculiar
construction, and one that was made especially
for the purpose. AS rule bright comets are
found near the sun. As soon as darkness comes
on sufficient to permit faint stars to be seen 1
m,
western. and northwestern horizon starting as
low down as possible aud sweeping in horizon
tai zones upward toward the zenith. In the
morning sky sweep in the eastern portion of
the heavens and from the zenith toward the
horizon. The eye-piece of my telescope ia 40
constructed that am able to observe at one
time about degree and half OF the sky, or,
In other words, If the moon was about three
times as large as at present it would lust fill
the heid OF view as seen in the eye-piece.
BY having SO large field l am able to sweep
rapidly and at the same time observe all OBJ
jects that appear In the telescope.
HOW THEY APPEAR.
"Comets as rule first present themselves to
our view in the form of watery-looking nebu-
lous mass of matter with slight central con-
densation. 1t commences to grow brighter,
and shortly bright point or nucleus is seen.
IL the comet is large and approaches relatively
near the earth a tail is observed to follow it.
The comet may continue to grow brighter until
1t bursts forth before our eyes in all the splen-
dor OF such objects az the great comets of 1S43,
1858, 1851, 1874 and 1882. The average of those
that rush into our system are small or too far
away from the earth to make much of a show
and their presence is known only to observers
who are interested in that particular branch of
astronomical science. The great obstacle, OBJ
servers searching for comets have to contend
with is the nebule that are scattered all over
the heavens. A faint comet and faint nebula
are strikingly similar in appearance, and
comet-seeker must be thoroughly conversant
with all nebuiB that can be seen in his tele-
scope to be able TO detect the former from the
latter.
The true character of a cometary looking
object Is soon decided after it has been exam
med. Nebul8 do not move, but retain their
relative positions with respect to the stars sit
uated near them. A comet on the contrary is
continually in motion, and an hours time after
its discovery is generally sufficient to observe
1t approach and pass a star situated near it.
lin the United States there are two observ-
ers besides myself who are constantly engaged
in this branch of astronomical research
namely, Prof. Brooks, Of Geneva, N. Y, and
Prof. Barnard Of the Lick observatory on
Mount Hamilton.
"THE TOTAL NUMBER OF COMETS
that have been discovered, and of which we
have accurate observations is something less
than five hundred For the past fifteen to
eighteen years the average has been three or
four year. Some time during the period from
1909 to 1912 one Of the most magnificent comets
of all ages will return to our view This is the
great comet known as Halley's comet, whose
period Is about seventy-fve years. This OBJ
ject has now passed its most distant point from
the sun, and is returning to us. Those of us
who live until 1912 will have the pleasure of
seeing this beautiful object, which has been
out in space on q three-quarters of q century
journey far beyond the orbit of Neptune come
back again to our sun and fulfill that great law
that controls all heavenly bodies, the law of
gravitatiOn."