Skywatch - 2021 - 32

J U N E | 2021
The Summer Triangle, with corners marked by Vega,
Altair, and Deneb, stretches across the Milky Way's
Great Rift. This dark lane, formed by opaque molecular dust clouds, stretches from Cygnus to Sagittarius.

Vega

Deneb

Altair

wooden furniture, old clothes, and even
the hulls of rowboats balanced precariously atop the eclectic heap.
Once the Sun has set. The Sun does
eventually set during June nights (except
for at latitudes above the Arctic Circle),
and for mid-northern latitudes and
farther south summer skies darken suﬃciently so that stars and planets emerge.
Let's fi nd some summer asterisms.
Turn the map so "Facing East" is at
the bottom. Now, go outdoors and actually face east. Look a little more than
Dusk, June 11-13
45 minutes after sunset
Moon
June 13

GEMINI
Mars

Castor

Pollux
Moon
June 12

10°
Venus
Procyon

Moon
June 11

Looking West-Northwest

AKIRA FUJII

S The

waxing crescent Moon, just one day old,
sits lower right of Venus in Gemini on the 11th.
Watch as the crescent grows bigger and rises
higher each subsequent evening, positioning itself
almost directly above Mars on June 13th.
32 SK Y WATCH 2021

halfway from the horizon to the zenith.
The brightest star you see is Vega, or
Alpha Lyrae, in the Lyre. Let's go fi nd
two more Alpha stars. Down to Vega's
lower left is Deneb in Cygnus, the Swan,
and farther to Vega's lower right is
Altair, in Aquila, the Eagle. These three
brilliant sparklers make up the Summer
Triangle. This asterism stretches across
the Milky Way's Great Rift, and in a
dark sky you'll see this dark lane formed
by opaque molecular dust clouds.
Higher up in the sky than Vega is a
boxy asterism called the Keystone in
Hercules. This quadrilateral is formed
by Pi, Eta, Epsilon, and Zeta Herculis.
Look between Eta and Zeta, a smidgen
closer to Eta than Zeta, and you should
see the season's best globular cluster,
M13. Consisting of some 300,000 stars,
under dark skies M13 should be visible
to the naked eye. In binos it turns into
a tiny, soft ball of light, while telescopes
reveal spidery, sparkly arms stretching
out from the cluster's center.
A pretty summertime constellation is
Corona Borealis, the Northern Crown.
You'll fi nd it roughly midway between
Arcturus and the Hercules Keystone.
The jewel in the crown, the constellation's brightest star, goes by two names:
Alphecca (Arabic for a broken circle) or
Gemma (Latin for jewel).
Even while you bask in the glory of
the Sun as it reaches its annual apex,
take advantage of June nights to admire
summer's delightful patterns.

PLANETS IN
JUNE
After the year's best showing in May, Mercury takes June off to bask in the Sun, or at
least, its glare. The innermost planet will be
unobservable all month and reaches inferior
conjunction with the Sun on the 10th.
Venus is very gradually gaining altitude
at dusk and by mid-June sets roughly 1½
hours after the Sun when it gleams at magnitude -3.8, well earning the title of Evening
Star. Its closest encounter with the Moon
happens on the evening of the 11th, when a
beautifully earthlit lunar crescent sits about
2½° to the lower right of it. The gap between
Venus and Mars closes from 25° on the 1st
to just a shade more than 7° by the 30th.
June sees Mars change its celestial
address as its eastward motion carries it
from Gemini into Cancer on the 8th. It's
joined there by the crescent Moon on the
13th. Cancer's deep-sky gem is the bright
open cluster M44, also known as the Beehive. Early on the evening of the 23rd, the
Beehive has one extra bee: 1.8-magnitude
Mars. This'll be a wonderful sight in binoculars and especially in a low-power telescope.
Seek out a viewing location with a relatively
unobstructed west-northwest horizon.
Rising shortly before midnight, mid-June,
is magnitude-0.5 Saturn. It's smack-dab in
the middle of the ﬂattened V shape of Capricornus. Trailing it is -2.5-magnitude Jupiter, which rises roughly an hour after Saturn
and is nearly 20° east of its neighbor on the
15th. Before dawn on June 1st, the lastquarter Moon sits a little more than 5° below
Jupiter. At the end of the month, the Moon
buzzes by Saturn on the morning of the 27th
and is near Jupiter on the 28th and 29th.

Historical Events
6/2: Giovanni
Battista Donati
spies Comet Donati
(C/1858 L1), the
fi rst comet to be
photographed, 1858

6/5: Charles
Messier
discovers
M20, the
Trifid Nebula,
1764

Skywatch - 2021

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