Skywatch - 2021 - 36

J U LY | 2021
known as the Small Sagittarius Star
Cloud. Under skies free from light pollution, it's visible to the naked eye on
moonless nights. Wafting up from the
spout are the little cloudlets M8 (the
Lagoon Nebula), M20 (the Trifid), and
M17 (the Omega).
You can also spot M8 under dark,
moonless skies with the naked eye. It's
delightful in binoculars; adding magnification will bring out a bright line of
four stars, the middle two of which are
enveloped in a glowing cloud. Through
a telescope you should see the handful of
stars swell into a cluster. Nearby M20 is
also a great target for scopes.
The globular cluster M22 lies a little
more than 2° upper left (a bit narrower
than two fingers held out at arm's length)
of Lambda Sagittarii, the Teapot's
pointed lid. When he first saw it in 1764,
Messier described it thus: ". . . this nebula
is round, contains no stars . . . ." In binoculars, M22 appears as a small patch
of light, but you'll want to see it through
a scope (even a 4-inch will do). Contrary
to what Messier saw, it's big, bright, and
beautiful, and higher magnification will
reveal an amazing swarm of stars.

Now move back across the top of the
Teapot to a pair of stars in the Scorpion's
stinger known as the Cat's Eyes - upper
left of this bright pair is a couple of open
star clusters. M6 and M7 are naked-eye
objects in dark skies far from city lights,
and they're superb in binoculars - in
fact, M7 is so big and bright that binoculars are really all you need to see it well.
A telescope at low magnification will
bring out M6's "jewel box" beautifully.
Next, find the smoldering red supergiant Antares, the heart of the Scorpion.
The name comes from the Greek "antiAres" where here the prefi x "anti-" refers
to "like," in reference to the similarity
of the star's color to that of the planet
Mars (Ares is the Greek counterpart
to the Roman god of war). A smidgen
more than 1° (one finger held up at outstretched-arm's length) right of Antares
is another globular cluster, M4. You'll
need binoculars, at least, but it'll still be
only an indistinct glow. A 4- or 6-inch
telescope will help M4 blossom and show
the pinpricks of individual stars.
Our introduction to Messier's marvelous objects is a wrap - may your
July nights be fi lled with fuzzy delights.

Dusk, July 11-13

Dawn, July 24 - 26

45 minutes after sunset

45 minutes before sunrise
Jupiter

10°

LEO

Moon
July 26

G
Moon
July 13

CAPRICORNUS

Sickle
Moon
July 25

Moon
July 12

Saturn

PLANETS IN
JULY
Mercury returns to the dawn sky, where
it remains visible until July 23rd. As July
opens, the tiny planet shines at magnitude
+0.8. Mercury climbs highest at dawn on
the 10th, when it gleams at magnitude
-0.3. On the 8th, it pairs up with a very
thin, earthlit lunar crescent, which sits
roughly 4½° to the left of the planet.
Venus continues its slow climb at dusk
but is momentarily stalled. However, its
July calendar is dotted with a few notable
encounters. The ﬁrst of these is on the 2nd,
when it's closest to the Beehive Cluster
(M44) in Cancer; bring binoculars. At dusk
on the 11th, Venus, Mars, and a thin waxing
crescent Moon form a lovely, 6°-wide string.
And on the 12th and 13th, Venus will be
closest to Mars, passing within just ½°. Continuing eastward, on the 21st Venus pulls up
to within 1° of ﬁrst-magnitude Regulus.
Mars is ﬁnally going away. It's in some
ways ﬁtting that it has a close encounter
with Venus this month as a sort of last
hurrah before exiting the celestial stage.
After the 23rd, Mars will be lost to evening
twilight, and we won't see it again until it
reappears at dawn in late November.
Both Jupiter and Saturn adorn the late
evening sky. At mid-month, Saturn rises a
little before 9:30 p.m. (local daylight-saving
time) and is followed about an hour later
by Jupiter. Plan your observing session for
around 3 a.m. when they'll be straddling
the meridian and moderately high in the
south. Saturn is at magnitude +0.3 and
positioned near the middle of Capricornus,
while Jupiter gleams at magnitude -2.7
from western Aquarius.

Regulus
Venus

Moon
July 11

Mars
Moon
July 24

0.6° apart

Looking West
S Left:

Looking Southwest

Look below Leo's Sickle to see Mars and Venus adorning the western horizon after sunset. A
smidgen more than ½° separates the two on the 12th and 13th. Watch as the waxing crescent Moon
glides by starting on the 11th. Right: Regal Jupiter and ringed Saturn join the waning gibbous Moon at
the end of the month.
36 SK Y WATCH 2021

Historical Events
7/1: Lexell's Comet
(D/1770 L1) passes
closer to Earth
than any other
comet in recorded
history, 1770

7/4: Chinese
astronomers fi rst
note light from the
supernova that
created the Crab
Nebula (M1), 1054

Skywatch - 2021

Table of Contents for the Digital Edition of Skywatch - 2021