Sky & Telescope - April 2020 - 47

Jupiter is only 6° west of the pair at that
time, and Mars has moved just a bit farther eastward from its closest approach
of less than 1° from Saturn on the ﬁnal
morning of March. At the beginning of
April, Jupiter greatly outshines the other
two worlds with its -2.1-magnitude
radiance, while Mars and Saturn are
nearly as bright as each other; Saturn
glows at magnitude +0.7 and Mars at
+0.8. Be sure to compare their colors
with your naked eye and in binoculars.
All three planets brighten slightly
during the month. Jupiter increases to
magnitude -2.3, Saturn to +0.6, and
Mars to +0.4. Unfortunately, Mars
spends the month gliding swiftly away
from Saturn. On April 9th the group
of planets are almost equally spaced,
with Saturn in the middle, about 52/3°
from Jupiter and Mars. But Mars speeds
on, almost crossing the entire width of
Capricornus as it puts more than 19°
between itself and Saturn by month's
end. Meanwhile, the gap between Jupiter and Saturn shrinks slightly to 5°,
with Saturn in westernmost Capricornus and Jupiter just over the border in
easternmost Sagittarius. As April winds
down, Jupiter and Saturn rise around
1:30 to 1:50 a.m. local daylight time -
almost 1½ hours before Mars.
During April, the apparent diameter

December
solstice

Uranus

Venus

Sun

Jupiter

Neptune
Saturn

The curved arrows show each planet's movement during April. The outer planets don't change
position enough in a month to notice at this scale.

of each planet grows slightly, from 37″
to 41″(Jupiter), 16″ to 17″ (Saturn) and
6.4″ to 7.6″ (Mars). Use your telescope
to see if you can detect the gibbous
phase of the Red Planet (its disk is less
than 90% lit throughout the month).
Meanwhile, Jupiter and Saturn reach
quadrature (90° west of the Sun) on
April 15th and 21st, respectively. As
a result, the two gas giants cast their
shadows far to the side, permitting bet-

Dusk, April 24 -27
1 hour after sunset

α Cap
Venus
Moon
Apr 26

Jupiter

Saturn
Moon
Apr 14

Mars
Moon
Apr 15
Moon
Apr 16

Aldebaran

Moon
Apr 25

Moon
Apr 24

Looking West

ter views of Jupiter's shadow eclipsing
the Galilean satellites, and enhancing
the three-dimensionality of Saturn's
globe and rings. Those rings are now
slightly less tilted (21°) than they've
been over the past several years.

MOON PASSAGES
The Moon is at its nearest for 2020 at
17:59 UT on April 7th, just 8½ hours
before it reaches full. (Expect to hear
the phrase "supermoon" bandied
about.) The Moon is passing through
last-quarter phase as it moves from well
right of Jupiter on April 14th, to close
below Saturn on April 15th. Finally, on
April 16th it's positioned not far lower
left of Mars. When the Moon returns to
the evening sky as a thin waxing crescent, it passes by the Hyades to the right
of Aldebaran - and very near Epsilon
(ε) Tauri - on April 25th, and sits far
left of Venus the following night.
¢ FRED SCHAAF teaches astronomy
at both Rowan University and Rowan
College in Gloucester County, southern
New Jersey.

TA U R U S

Pleiades

Looking Southeast

Mars

ORBITS OF THE PLANETS

1 hour before sunrise

β Cap

Mercury

Earth

June
solstice

Moon
Apr 27

Dawn, April 14 -16

Sept.
equinox

March
equinox

t These scenes are drawn for near the middle
of North America (latitude 40° north, longitude
90° west); European observers should move
each Moon symbol a quarter of the way toward
the one for the previous date. In the Far East,
move the Moon halfway. The blue 10° scale bar
is about the width of your fist at arm's length.
For clarity, the Moon is shown three times its
actual apparent size.
sk yandtelescope.org * APRIL 2 02 0

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Sky & Telescope - April 2020

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