Evening star., 1925-06-28
THE STARRY SKIES IN JULY


A glance at the map, figure /, shows
this is an unusual month In respect
| to the planets. The positions of six
or the seven planets are indicated on
the map. Uranus alone Is not shown
| as that planet is not visible to the
naked eve. 1t is in the constellation
Pisces. which is below the eastern
horizon. The Ave naked-eye planets
may be seen Simultaneously (Neptune
| is also invisible to the naked eye)
These facts alone would make the
month very unusual. l do not recall
when these things have occurred be-
fore. Mercury. Venus and Mars are
| moving rapidly among the stars. and
their positions at the beginning of the
month are such that they set before
3 pm. The positions at the end of
the month are shown on figure l.
The paths of Mercury, Venus. Mars
and Neptune during July are very
| interesting and are shown in detail in
| figure .. At the beginning of the
month Neptune is in the lead. That
planet. however. is the farthest from
the sun, moves very slowly and
| changes It's position but little during
| the brief interval of month. 1t re
quired 165 years to complete its i'm
| mense circuit about the sun. Next
comes Mars, which Is next to the
earth in order of distance from the
sun. with d greater distance than that
| of the earth. Then follow Venus and
Mercury, the two planets which are
closer to the sun than the earth. The
rates at which these planets move are
quite unequal. The most exciting time
in this interplanetary handicap race is
on July 10. On that day Mercury over
takes Venus and passes 1t. About an
hour later Mercury overtakes it's next
rival. Mars, and an hour later still
Venus overtakes Mars. On July 10
Mercury overtakes and passes the
plodding Neptune. The next day
Venus on the heels of the heeting
Mercury, also passes Neptune. But
the pace has proven too fast for Mer-
curry, who tires and IL overtaken by
Venus on July 80 on the homestretch,
and Venus breasts the tape the win
| ner. Two hours later on July 80 Mars
passes Neptune in time to finish the
! month in third place. Had it passed
| three hours earlier we should then
| have had the planets in just the re-
verse order from that in which they
began the month, and the last should
have been first and the first last. The
fixed star Regulus (at A, figure y
stands as a spectator at point of
vantage near the finish.
To add interest to the occa aston, the
moon comes flying along the track
| OF the planets The moon. being the
satellite of the earth, is disqualified as
a competitor in this interplanetary
| race. He comes along in an aero
| plane or motorcycle and passes the
starting point of Mercury July 20, 5
| am, and Mars July %, am, Nep-
tune pm and Venus 10 pm. on the
same day. and Mercury, at that time
| leading in the race. at / am. July %
and passes the finishing point late
| that day.
AS already stated. three Of the COM
petitors are closely punched on the
evening of July 10. The positions on
this evening are shown on a diagram
with a much larger scale in figure g.
In the afternoon the competitors are
In the order in which they started the
month, namely, Mars. Venus and Mer-
curry. At 9 pm, Eastern standard
time, Mercury passes Venus. The
planets at this time are but six min
utes. or tenth of a degree, apart To
assist in realizing the meaning Of the
| units. a circle is drawn on the figure
to represent the size of the moon s
disc (Which is 81 minutes in diameter)
on the same scale. At no time is the
moon in that position. The naked eve
cannot see separately two stars which
are much closer than three minutes
apart.
When one planet passes another it
is said to be in conjunction with it.
Such conjunctions are not rare. There
are 20 this year. Five Of these are
conjunctions of Mercury and Venus.
There are also SO conjunctions of the
moon with the planets. The conjunc-
tion of the moon with Mars at am
July p, which will not be visible. is
the only one Of these 109 conjunctions
closer than six minutes. At 10 pm
July 10 Mercury passes Mars at a dis.
tance of Is minutes. There is but one
planetary conjunction this year. ex-
ceptfng those occurring this month, as
close even as % minutes, and only two
conjunctions of the moon and planets
are closer. This shows what a rare
event it Is which occurs on July 10, for
We have not only an exceedingly close
conjunction of Venus and Mercury
but also a close one in the case of
Mercury and Mars and in the case of
Venus and Mars. Moreover the three
conJunctfonS occur in the space of two
hours, and the most remarkable thing
of all is the fact that the three planets
during. this time are so closely clus-