Evening star., 1925-03-29
THE STARRY SKIES IN APRIL,
By Prof. Barton Of the University of Pennsylvania

There are no unusual astronomical
events predicted to occur this month.
The eclipse season is over and no
more will occur until the next
eclipse season comes, in July and
August, but even then we shall not
see the eclipse here. Eclipses are
not Of such frequent occurrence that
each one is not an interesting event.
The planets also, at times, come into
positions which make a special in
terest in them at that time; they
may be closely clustered, or they
may be covered by the moon, or
Mercury or Venus may pass between
us and the sun, or they may be
unusually bright and conspicuous, as
was Mars in 1924 During April,
however the planets are doing moth
ing of particular interest. The posi-
ton of Mars at the beginning and
at the end of the month is marked
on figure 1. The planet is in the
constellation Taurus throughout the
month. 1t may be seen to move past
the star Aldebaran at A during the
month. Both the planet and the star
are reddish in color. Mars is half
magnitude fainter than Aldebaran.
1t is now within half a magnitude
of its faintest, which Is reached
when 1t is too close to the sun to
be seen. The position of Neptune
in Leo is marked, but the planet is
not visible to the naked eye. Saturn
is in Libra, just on the horizon
little south of east. Jupiter Is in
Sagittarius and visible late In the
night. Uranus, which is not visible
to the naked eye, is in Pisces. On
April "a Venus passes the sun, after
which time it is east of the sun and
an evening star. 1t will not be far
enough from the sun to be seen for
several months. For a few days at
the first Of the month Mercury may
be seen, but must be looked for soon
after sunset a little north of west,
close to the horizon 1t is then as
bright as the star Rigel, the bright
est star in Orion, at B, familiar to
many.
Other bright stars shown on figure
l are Sirius at c, Vega at d. Capella
at E, Arcturus at F, Procyon at G,
Betelgeuse at H, Pollux at J, Spica
at X, Regulus at NJ, and Castor at
The Next Comet.
shall see the next comet. Under
standing the question to mean a
comet visible to the naked eye, 1
reply that there will be one in 1887,
when Halley's comet returns, and
that l cannot say more except that
it is likely there will be several be-
fore that time, but when 1 do not
know. There may be one this month; /;
I know no more than you. The i'm
preston that astronomers are able
to predict the, return of comets has
been given undeserved emphasis by
reason of the predicted return of
Halley's celebrated comet. The path
of this comet is the eclipse shown
in figure 2. 1t was seen when 1t
was near the sun and the earth in
1910, as predicted by astronomers.
1t can only be seen when near the
earth and sun, because at other
times II is too far away. Hence 1t
will be seen at intervals Of the time
required by the comet to make the
circuit of its orbit, II years. 1t was
last seen in June of 1911, but we
know well that 1t is now in the part
of it's path between the orbits of
Uranus and Neptune, and that it
will be farthest from us in 194s, and
back again in the vicinity of the
earth in 1887.
1t is now believed that practically
all comets move in such elliptical
paths, and that after an interval
long or short, usually long, they will
return to the part of the path in
which they were when seen. 1t may,
however, happen that upon their
return the earth may not be as
favorably situated and they may
pass the sun unnoticed. Some comets
are seen but for a very short time,
and in most cases the time in which
we see them is very short compared
with the time taken to move around
the whole orbit, as none is seen
beyond the orbit of Jupiter. They
are also poorly defined objects for
which accurate determination of the
positions are not possible. So, while
we can tell the shape of the comets
path near the sun, 1T is almost al
ways impossible to tell the length