Evening star. [volume] (Washington, D.C.) 1854-1972, 1882-02-04

SOmeahimg About the Moons Of MarS-
The Smallest Heavenly Bodies
kn0Wn-Reccas Observation . made
by Prof. Hail.

Something AAeus the Moons of Mar~-
The smallest Heavenly Bodies
kneWn-Reccas Observation made
by Prof. Hail.
For ages it was believed that the pl anet Mars
was moonless. The inhabitants of that planet,
which presents in many respects, SO far as tele-
scopic observations 60. a striking resemblance
| to the earth, 1t was supposed knew no luminary
at night, except the stars spangng the
hemisphere. The Martial newspapers, never it
was thought, were guilty of stale jokes about
corporation moonlight, and the Martial poets
lacked material for embellishiug love-sick bal
lads The popular error In this respect was,
however, corrected few years ago 10y Prof
Asaph Hall, of the Naval Observatory in this
city who discovered that Mars. instead Of having
no moon, was fortunate in the possession of
two particularly lively little satellites. This
discovery was made in August. 1877. when 1t
happened that a particularly favorable oppor-
tunity for observation was afforded by the
fact that the planet was near its OPP
position, and its perineiion at the same
time. Observations were then sus-
pended until the planet came again in oppos-
ton. in November. 1879. The recent oppos-
ton OF the planet has afforded further oppor-
tunity for investigation, which has not been
neglected by the astronomers. The existence
of these satellites whose discovery is of such
comparatively recent date, is of course as we'll
known now as any other scientific fact among
students of astronomy. but as it is not a matter
that is apt to affect the markets or the political
situation, it is not generally known among
other men.
THE GREAT DISCOVERY
has been celebrated in exhaustive memoirs. and
pamphlets filed with columns Of cabastic signs
and strange figures, and the astronomers of the
world have testified to the scientific Importance
of Prof Halls discovery by aiming batteries of
| telescopes at Mars wherever that planet appears
| in opposition.
The discovery was made on the night of An
gust IL, 1877 when Prof Hall found a small
object about 50 seconds east of the planet.
Prof. Hall observed 1t several nights before an
nouncing his discovery, first satisfying himself
as to the motions of the body. While observ-
planet, which proved to be a second and inner
satellite. These bodies are rated as the small
| est heavenly bodies as yet known. Their most
extraordinary feature is the proximityof the
revolution. 1t PUSHES around the planet In
hours 80 minutes. The outer one makes the
Journey in 50 hours Is minutes.
THE SIZE OF THE SATELLITES.
In the large telescope these bodies are seen
only as points of light, and the only datum on
which an estimate of their size can be foundedis
the amount of light they give From this it has
been calculated that the diameter Of the outer
satellite is from to 10 miles. and Of the inner
and brighter satellite, from 10 TO 40 miles. The
bodies were christened very soon after their dis
cOvery, the inner one receiving the name OF
PhoboS, and the outer one the name of DEMOS.
Mars was In opposition again just before the be-
ginning OF the present year. Prof Hall caught
sight of the satellites first on the 18th of Novem-
Der, and continued his observations until Janu-
airy 18th: One result of his observation was a
practical veriiication of the ephemerides of the
satellites, calculated upon the material fur
niSheG by the first observations. In 1873, when
he renewed his observations. he found the two
bodies almost exactly in the same spot in relation
to the planet. as he had predicted This eXpe-
rience was repeated during his recent observa-
tons. Owing to the small orbit and rapid mo
ton of these bodies, of course, it requires very
nice calculations to determine what will be their
relative positions at some given day and hour in
the future.
WHAT PROF. HALL SAYS.
zone of the most important objects to be
gained in observing these satellites" said
Prof, Hall to STAR reporter, sis the determi-
nation of the mass of Mars. Owing to the posi-
ton of the planet during the recent opposition.
observations have been directed towards detect
ing the difference in the planes of the orbits OF
the satellites Their orbits are practically on
the equator of the planet. The earth was
almost in the plane of the equator of Mars
so that the orbits OF the satellites as seen from
the earth would appear to be long ellipses, MAX
ing it easy to detect the variation in their
planes"
Yes" continued the Professor. '.the rapidity
of revolution Of Phobos is wonderful The satei-
lites cannot be seen, of course, against
the surface of the planet / have seen
PhObOs on one side Of the planet at
its eastern eiongation and on the same
night, four hours later, observed it on the other
side. 10 an observer on Mars Phobos would
subtend quite a large angle-perhaps appear
as large or larger than our moon does TO u.s.
There is another singular thing about these
satellites. PhObos reyolveS around the planet
from west to east. and peimos from east to
west Phobos is less than four thousand miles
away-abOut the distance
BETWEEN WASHINGTON AND VIENNA.
If the satellite was inhabited, with such a
telescope as ours an observer on Mars could tell
1t, and could see the cities"
The existence Of the satellites and their ex-
traordinary relations, furnishes fund of mate
rial for some imaginary writer like Verne To
the people of Mars Phob0s moves across the sky
ike fiery dragon. spanning the whole heavens
in little more than three hours. The prox-
unity OF the two moens to their mother planet
and their rapid revolutions. make eclipSes fire.
quent. but of short duration. The relationship
between the motions of the satellites is similar
to that discovered in the GASES of the planets
Jupiter and Saturn. The inner one revolyes in
very nearly one-fOurth the period of the outer
one. The satellites will not be observed again
until the planet again comes in opposition, in
January, 1884.
THE FINANCIAL VALUE OF LIFE
An Article by John w. Guiteau-A
Young Mans Chances of (aiuiuy +.