The San Francisco call., 1905-02-28

BERKELEY, Feb. 27.-Rivaling in
Importance the discovery by Professor
Perrine of a sixth satellite of Jupi-
ter, which discovery was made last
month at the Lick Observatory, comes
a second announcement to-day from
Director Campbell, who informs Pres
ident Wheeler of the State University
that Professor Perrine has discovered
a seventh satellite.
In the opinion of Director Campbell
this latest discovery of Professor Per-
rine reveals zone of the most inter-
esting bodies in our entire solar sys-
tenn" The facts concerning the dis
coyery and the circumstances under
which the Lick Observatory astron-
omer made his extraordinary find in
the heavens are contained in the fol-
lowing letter to President Wheeler:
Lick Observatory, University of California.
February 81. 1905.
1t gives great pleasure to announce that
another satellite of Jupiter has been discov-
cred by Assistant Astronomer Perrine of the
Lick Observatory staff. 1t will be known as
the seventh satellite. The discovery was act
ually made January q last but announce
ment OF the fact was not justified until the
present time.
The sixth satellite first observed by Profess
sor Perrine on photographs taken early in De-
cember, next recorded on the photographs
OF January 2, 3 and 4, and public announce
ment of the discovery was made on January 8.
The following day Mr.. PeTrine resumed his
comparative examination of the negatives Sc
cured on the last three dates. and was re-
warded by discovering the image of a very
faint body which changed its position from
night to night. 1t moving in such way
that the probabilities were in favor of It's be-
ing satellite Of Jupiter; but, at the same
time, the possibility existed that 1t one
Of the large group of asteroids whose orbits
lie between those of Mars and Jupiter. This
question could not be resolved until obser-
vations Of the new body had extended over
several weeks Unfortunately, the unfavorable
weather in January prevented the securing of
exposures long enough to record this faint
did not fully resolve the doubt as to the char
acter Of the object Photographs secured by
computations based upon them, have enabled
him to decide definitely that this body is a
satellite of Jupiter. It's Photographic magni-
tude seems TO be about the sixteenth. The
number of telescopes which would permit
visual observations of it is therefore limited.
The direction of this seventh satellite from
Jupiter on the evening of February %, was
81 degrees east of north, and its distance
from the planet was nineteen minutes of arc.
Its motion is carrying it southeasterly at the
rate of one minute Of an arc per day. Its ap-
parent motion around Jupiter is in the direc-
tion that astronomers would describe as direct
The apparent motion of the sixth satellite,
on the contrary, is in the reverse direction.
Whether these satellites are actually revolv-
ing around Jupiter in the same direction as
the five inner satellites. or in the opposite
direction cannot be stated at the present time.
orbits II MAKE eonsiderasle angle with each
other, and that they make large angles with
the plane of Jupiters equator. The distances
OF the two satellites from Jupiter not very
unequal in both cases probably lying between
six millions and eight millions of miles. Their
corresponding periods of revolution around the
planet would, therefore, be seven eight
months in each case. On many accounts these
two satellites promise to be among the most
interesting bodies in entire solar system.
Mr.. Perrine is computing their orbits around
Jupiter, but several days viii probably pass
before further facts can be communicated. 1t
is also pleasure to say that these noteworthy
discoveries were made from photographs
cured with the Crossley reflector whose mod
ern remounting. substantially completed about
December l.. was provided for by funds from
the University Of California and from Mrs.
Phoebe A. Hearst. the undertaking OF the work
having been made possible by the generous
contribution of Mrs. Hearst for this purpose.
w. w. CAMPBELL.