The Indiana State sentinel. [volume] (Indianapolis) 1868-1895, 1894-11-28
ENCKE,s COMET.
Its Return Trip and What Ii Tells
AstrOuOmers.


Encke's comet. which has just been dis
covered on its return by the Italian as
tronomer, Ceruui, who has a private OBJ
servatory in the southern portion of the
kingdom, is one of the best-known of the
Jupiter group Of comets. This group, so
far as known. consists of nineteen OBJ
jects, all Of which are members Of our
solar system and are revolving about our
sun in orbits from three and one-half
years TO about double that time. The
group is so-called because there is every
reason TO believe these wanderers were
intercepted in their path through space by
the giant planet Jupiter, and perturbed
OF which lies in the neghborhood of the
orbit of this planet.
Encke's comet is the most noted OF this
group, having been known to astronomers
for upward Of a century and having been
sufficiently we'll observed to conform very
closely TO its computed path. 1t was first
seen by Mechain of Paris on Jan. II, 1856,
and was again discovered by Miss Caro-
line Herschel in November, 1895, and after
few days by other astronomers. 1t was
again observed in 1905, but none of the
astronomers at the time knew of the iden-
tity of the objects which they saw. In
the winter of 1888 il was visible for
some seven weeks, and Eacke busted him.
self with the computation of its orbit. IN
a remarkably short time he had his COM
putation finished and was able to show
that 1t was moving in an orbit of three
and One-third years period, that the COM
cts above enumerated were identical with
IL and that 1t had approached the sun
eighteen times in the intervals unob-
served.
Encl1e next computed the time of its re-
turn, announcing this date as May "a,
1922. having been delayed on the way some
nine days by the attraction of Jupiter,
and according to this time table. the OBJ
ject was again observed on its return.
This computation of Encke's was a most
remarkable one. involving as it did some
or the most intricate and labOriOus prob
lens known to the astronomers of the
time.
Encke himself very early suspected that
there was some cause of disturbance in
the motion Of the comet, for despite his
calculations Ii completed its orbit in some
two and one-half hours less than the
computed time. This discrepancy, small
as it seems, is easily discerned by astron-
omers, and a continuation of the shorten
ing Of the orbit Of the comet is now no
tlceable. The explanation of il is quite a
problem to astronomers, but it is thought
to be a proof of the existence of a resist
Ing medium pervading space the friction
Of which retards toward light bodies
which move through it.. The questions
which depend upon this assumption are
some Of them quite interesting for Ii is
continue sufficiently long, and the course
Of the comet be not too much disturbed
by the attraction of the planets, the comet
viii eventually fall into the sun.
The comet has been Of quite little serv-
ice to astronomers in the consideration Of
the mass of attractive force Of the planet
Mercury This Planet, having no satellite
known TO US. has not been accurately
weighed, or at least not as compared with
the other planets of our system. In 1888,
however. this comet approached sufficient
ly near to the planet 10 be affected by its
attraction. and from the facts here OBJ
served astronomers have been abe to de-
fine their knowledge Of the mass of Mer-
curry.
Encke's comet is a modest little object,
always of the greatest interest to astron-
omers possessing moderate instrumental
means. presenting as it does many rather
remarkable features as to its tail and the
distribution Of its light. 1t is moving
through space completing its orbit time
after time. almost with the regularity Of a
train on well-cOnducted railway, and on
it's successive returns 1t may be found al
ways within the fed of a telescope direct
ed to its computed place, a continual
tribute TO the accuracy and industry Of
our astronomers.-Boston Transcript.