Sky & Telescope - May 2020 - 46

MAY 2020 OBSERVING
Sun, Moon & Planets by Fred Schaaf
To find out what's
visible in the sky from
your location, go to
skyandtelescope.org.

Five Planets Excite
The Evening Star slips away while the Red Planet gains size and brightness.

A

fter spending March and April near
its ultimate evening altitude, Venus
plunges down into the Sun's afterglow
in May and passes close to a climbing
Mercury. As Venus exits the evening
sky, Jupiter and Saturn make their
entrance late at night and throughout
May are the most closely paired they've
been in 20 years.
Last in the night's promenade of
bright planets is Mars. The Red Planet
rises several hours after midnight and
brightens rapidly to zero magnitude as
its growing disk begins to show a few
surface features in amateur telescopes.

DUSK AND EVENING
Venus begins May with a sunset
altitude of about 35° (for observers at
around 40° north latitude) and sets
almost 3½ hours after the Sun. But by

month's end the interval dwindles to
less than ½ hour.
As the month starts, Venus is at a
searing peak brightness of -4.7 and
situated a few degrees from 2nd-magnitude Beta (β) Tauri, El Nath. The sunset
altitude of Venus decreases to 23° on
May 15th to only about 3° by the 31st.
Over that same span, its brightness
drops from magnitude -4.6 to -4.2. The
current apparition ﬁnally ends when
Venus reaches inferior conjunction with
the Sun on June 3rd.
In a telescope, Venus begins May as a
crescent about 40″ tall and 24% lit and
grows to 50″ and thins to 11% lit on the
15th. That's a good date to try to see the
crescent with steadily supported binoculars - or even without optics, if you
have very sharp vision. Alternatively, try
looking at the planet through a piece

of cardboard with a roughly 1 to 2 mm
wide hole in it. (For more on sighting
Venus, see page 49.) As May ends, the
planet's razor-thin crescent is about 57″
tall and only a few percent lit.
Mercury ﬁrst becomes visible in
evening twilight around May 11th, as
a magnitude -1.5 object in the westnorthwest, well below Venus. The two
planets converge as Mercury climbs
noticeably higher and Venus sinks lower
each night. They come closest together
for North America on the evening of
the 21st, when Mercury glows about
one degree to the lower left of Venus.
By that date, Mercury has faded to -0.7
and its 6″-wide, 69%-lit disk contrasts
remarkably with Venus's 53″-wide,
6%-lit disk (which also has a much
higher surface brightness than Mercury's). For the rest of the month, while

Dawn, May 11-15

Dusk, May 21

1 hour before sunrise

30 minutes after sunset
Saturn

CAPRICORNUS
Mars
Moon
May 13

Moon
May 14

Jupiter

Moon
May 11
Capella

Moon
May 12

Moon
May 15

β Tau
10°

ζ Tau

Venus
Mercury

Fomalhaut

Looking South-Southeast

46

M AY 2 0 2 0 * S K Y & T E L E S C O P E

Looking West-Northwest
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Sky & Telescope - May 2020

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