The morning call., 1890-05-01
ASTRONOMICAL.
The Positions of the Planets Dur
ing the Month of May.
Ascertaining the Length of Day on the Planet
Mercury-What the Telescope Reveals.
The Southern Cross.

The planet Mercury, upon which many
| telescopes are now turned with more than
| ordinary interest, is at present an evening
star, and after sunset may be seen not far
| from the northwestern horizon. In marked
| contrast to the pearly whiteness of Venus,
| near which it glimmerS through the mists,
1.-THE sparkling one," as it was appropri-
| ately named by the ancients, has q yellow
| tinge, is smaller, swifter in motion and
| illumines the twilight hours but for few
successive days at each period of visi-
bility. 1t would not be easy to imagine
more pleasing study than careful observa-
ton each evening of its apparent motion
during its brief visit to the western sky. II
Venus, unmiStakable on account of its
size and Iuster, and Aldebaran, the nearest
fixed star of the first magnitude, be used as
landmarks, it will soon become evident
that Mercury is ascending toward the lat
ter until May 9th. when 1t may be found
nearly in a line with it. toward the north.
After this date, having completed its up
ward range. the little planet recedes rap
idly toward the horizon, being much lower
at a corresponding hour each night, and
passing Venus on the 9TH sets in sunlight
before the month is far advanced. During its
brief appearance it exhibits varying phases
llhC luOoc VI TIC mOOu, Dub llcS6 llbul-
festations of borrowed light make little
difference in its aspect to the observer not
favored with the advantages of magnifying
power. Students of astronomy may be
interested in knowing that its greatest
eastern elongation on May 9th is 90 49,,
that it passes its descending node on the
22d inst, and is in inferior conjunction
with the sun on the 29th.
THE SPARKLING PLANET.
To those who see the sparkling planet at
its greatest distance from the horizon it
seems surprising that Coperncus should
have died without ever behOlding the little
orb whose true position in the solar system
he was the first to understand. Probably
the heavy fogs on the banks of the Vistula,
near where he resided, account for the de-
privation. This swiftly moving orb, that
has hong tantaliZed astronomical gaze, send
Ing forth its golden glance and then reced-
ing from view without leaving any but
vague conjectures as to its surface and ak
lal rotation, was at one time supposed to
turn on its axis in about twenty-four hours.
But more recent observations refuted this
belief and brought little hope of reliable
discovery as to its condition. The present
cause of interest is the announcement by
Sehiaparelli, an Italian astronomer, that
various standings are to be seen on the sur
face similar to those exhibited by the planet
water. and that by means of those marks
Mercury has been found to rotate on its
axis In about lightweight days, the same
period III which II revolves around the sun.
Consequently, telescopes all over the world
are how leveed on the disc in order to con-
firm or refute these venturesome theories.
When the twilight hours are past and
Mercury and Venus are lost to sight, the
observer, favored with full view of the
starry vault of the month of May, by fol-
lnNinp the hOriyOnfal lima oil lyin
succession of interesting objects, COM
mencing with the great Orion, sinking
slowly in the west"
Sirius also sends its last CLEANS for the
season from the southwest, and at the end
OF the month 1t sets in the rays of the sun.
A SOUTHERN CONSTELLATION.
The Centaur, a southern constellation,
may be seen rising east of south, but being
partly invisible to observers south of the
tropics, the famous Alpha Centauri, of all
the liked stars whose distances have been
aScertalned the nearest to the earth,
reserves its interesting rays for more
southerly climes. San Diego, however, is
favored with a glimpse of the most
northerly star in the beautiful constellation
of the Southern Cross on clear nights in the
present season.
The planet Mars, of roseate hue, appears
in the southeast, and increases in apparent
size as the more swiftly moving earth over
takes 1t in Its course round the sun. BY
thus outsDeeding the ruddy planet, we
come in view of its fully Illuminated disc
May 9th, when it will be in opposition to
the sun, the earth being in liue between
them, but one-third of the distance nearer
to Mars. This will be the best opportunity
that will occur for observation of Mars
during the coming two years, as ii will be
only about 100000 miles distant. An
tares, the red-tinted star little to the
southeast, though often its rival in size as
well as in hue, is at present noticeably
smaller.
Vega, the clear, white star that glistens
at dusk in the northeast. is destined at
distant date to be the pole star of our
world, as the North pole is slowly inclin-
ing in the direction of this pearly orb. 1t
scarcely has its peer in brightness, though
mahy other stars OF first magnitude are SUI
perior in size; for instance Arcturus, seen
at the same hour directly east of the zenith.
CassiOpeia, the name of the stellar group
in which a brilliant new star christened, on
imperfect evidence, The Star of Bethle-
seen during the evening hours spangling
the northern mists close to the horizon. 1t
is not supposed that a modern stellar crea-
ton is about to illuminate the group; but
that temporary and periodic Outburst of
luminosity from faint orb that sinks to
inyIsiblllty for centuries Will be due in the
near future. This grovp completes the cir
cult of observation near the horizon.
Higher on the starry vault, Capella in the
northwest Gemini, The Twins, midway,
Procyon southwest and Regulus near the
meridian still glimmer in the western heav-
ems; while in the east the pale CLEAN of
Spca is seen some distance upward from
Mars and in striking contrast To its roseate