TO KNOW THE STARRY HEAVENS 
I2 5 
The Planets. 
None of the brighter planets are in 
good positions. Venus can be seen low 
in the west just after sunset. At the 
first of the month its position is outside 
the limits of our map. Its position at 
the end of the month is shown on the 
map. Jupiter and Saturn lie in Leo 
sponding position of Venus and with 
the sun. The angle whose vortex is at 
the earth between the lines joining the 
earth with the sun and with Venus is 
called the elongation of Venus. This 
angle reaches its greatest value on 
February 9, the angle then being a little 
under forty-seven degrees. Venus is 
Figure 2. The motions of the earth and Venus in 1921. 
just beyond the eastern limit of the 
map. They rise soon after nine o’clock. 
Mars passes Uranus January 9. A few 
hours later on the same day Venus 
passes Uranus. A few hours later still 
Venus passes Mars. At this time these 
three planets will be closely grouped 
but low in the sky. Mars is now near 
the Sun. It will be passed by the sun 
on June 28. It will not be in good posi- 
tion at any time during the year. Ju- 
piter and Saturn will be visible in the 
early evening from February until 
August. 
In Figure 2 we show the motions of 
the earth and Venus. Lines are drawn 
joining the position of the earth on 
each of the eight dates with the corre- 
then at its greatest eastern elongation. 
After this time the elongation de- 
creases until it becomes zero on April 
22, at which time Venus passes from 
the eastern to the western side of the 
sun. It changes from an evening to a 
morning star. Venus is then at inferior 
conjunction. Venus is then closest to 
the earth at a distance of about 26,000.- 
000 miles. Venus reaches its greatest 
western elongation on July 1. It is then 
visible in the morning before sunrise. 
The distance of Venus from the earth 
changes. It is not brightest when 
closest, for Venus shines only by re- 
flecting the sunlight which falls upon 
it, and when closest the illuminated side 
is turned away from the earth. \ enus 
