SKY THIS MONTH
Visible to the naked eye
Visible with binoculars
Visible with a telescope10°AURIGAGEMINIORIONTAURUS PERSEUSCapellaBetelgeuseVenus
MercuryMay 21, 30 minutes after sunset
Looking west-northwest36 ASTRONOMY • MAY 2020Whether you prefer
evening or morning
observing — or both — May
has you covered. Venus and
Mercury appear in the night
sky this month, offering fine
views during evening twilight.
Meanwhile, the morning sky
holds the magnificent trio of
Jupiter, Saturn, and Mars. All
three planets are improving as
they approach their respective
oppositions later this year,
which results in larger disks
when viewed with a telescope.
But first, let’s begin with the
inner planets in the evening sky.
Venus is the brilliant beacon
hanging in the western sky soon
after sunset. Shining at magni-
tude –4.7, it dazzles near the
northern horn of Taurus the
Bull. During the first week of
May, the Hyades and Pleiades
sit low near the horizon before
disappearing in twilight. Look
west an hour after sunset to
catch these open clusters before
low altitude fades them.
Venus sits 37° east of the Sun
on May 1, and stands 23° above
the western horizon an hour
after sunset. Its beautiful,24-percent-lit crescent disk
spans 39" when viewed through
a telescope. The world main-
tains a reasonable altitude
through the middle of May
as its separation from the Sun
diminishes. And on May 16, it
stands 11° high an hour after
sunset. By then, the disk of
Venus has grown to 50" wide,
but it’s even more slender, just
a 10-percent-lit crescent. As themonth presses on, Venus rapidly
descends deeper into twilight
and its altitude falls as it nears
June’s inferior conjunction.
However, there’s one more
event that observers may want
to catch: a conjunction with
Mercury, which is moving on
the far side of the Sun in the
opposite direction of Venus.
Mercury passes through supe-
rior conjunction May 4 andreaches conjunction with Venus
on May 21/22. Their closest
approach occurs during the
early morning of May 22, so the
best time for U.S. observers to
target the pair is on the previ-
ous evening, May 21, when they
stand slightly more than 1°
apart one hour after sunset.
At this point, Mercury shines
at magnitude –0.6 and Venus
at magnitude –4.4.
Telescopic views of Mercury
reveal a tiny 6"-wide disk that’s
69 percent lit. This vividly con-
trasts with the Venusian cres-
cent, which spans 53" as a
6-percent-lit crescent. Within
days, Venus descends out of
view. But at the same time,
Mercury climbs higher along
the ecliptic, making it relatively
easy to spot the rest of the
month. Look to the west-
northwest in a clear sky May 31
to find the innermost planet
hovering 8° high an hour after
the Sun goes down, shining at
magnitude 0.1.
Jupiter rises close to 2 a.m.
across mid-northern latitudes
May 1, and by May 31, it is up
by midnight. Look for the gasThe innermost planets share the evening sky (^)
MAY 2020
Venus
meets
Mercury
THE SOLAR SYSTEM’S CHANGING LANDSCAPE AS IT APPEARS IN EARTH’S SKY.
BY MARTIN RATCLIFFE AND ALISTER LINGA brilliant Venus shines to the
right of an overexposed crescent
Moon during twilight at Lake
Wendouree in southern Australia.
A barely perceptible Mercury
hovers below and slightly to the
right of Venus. BLACHSWAN/FLICKRThe innermost planets stand only about 1° apart above the west-northwestern
horizon shortly after sunset May 21. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY