Sky & Telescope - July 2022 - 50

JULY 2022 OBSERVING
Celestial Calendar
α
July 30, 1 am
Circlet
AQUARIUS
Saturn
PISCES
Jupiter
δ
Delta
Aquariid
radiant
CAPRICORNUS
Fomalhaut
β
10°
Action at Jupiter
JUPITER RISES well before 1 a.m. local
daylight-saving time at the start of July.
By the time civil twilight begins, the
planet has attained an altitude of better
than 44°. On the 1st, Jupiter resides in
the non-zodiacal constellation Cetus,
where it shines at magnitude -2.4 and
presents a disk 41″ across. By month's
end, Jupiter is up before 11 p.m. and
transits the meridian at roughly 5 a.m.,
just as the sky begins to noticeably
brighten with twilight.
Any telescope reveals the four big
Looking Southeast
A Meteor Shower for
Warm Nights
I'M EMBARRASSED to admit I've never
intentionally looked at the Southern
Delta Aquariid meteor shower. I've seen
a few members fly by over the years
and casually traced them back toward
Aquarius but have never given the
shower its due. This month, I have no
excuses. While the stream is active from
mid-July to mid-August, the peak occurs
on the morning of July 30th. With the
new Moon falling on the 28th, the timing
is just about ideal.
Because the shower's radiant is
located in southern Aquarius a few
degrees west of Delta (δ) Aquarii,
observers in the tropics get the best
view and might see 25 meteors per
hour between midnight and dawn.
But there's no need to sniff if you live
at mid-northern latitudes, where the
radiant culminates due south at about
30° altitude shortly after 3 a.m. local
daylight-saving time.
Up to a dozen meteors per hour
may scratch the sky from a dark site.
Be patient and enjoy the light show as
the Milky Way wheels westward and
Saturn, Jupiter, and Mars parade slowly
across the south. Just don't forget to
bring the bug spray.
The Southern Delta Aquariid shower
is rich in faint meteors because the
50 JULY 2022 * SKY & TELESCOPE
particles are dust-size and enter the
atmosphere at a relatively moderate
speed of 40 kilometers (25 miles)
per second. The display's origins can
be traced back to a comet that broke
up about 9,500 years ago. From that
chaos, Comet 96P/Machholz arose,
along with near-Earth asteroid 2003
EH1 (responsible for the Quadrantid
meteor shower), and the Marsden and
Kracht comet groups. Material shed
by Comet 96P is responsible for both
the Southern Delta Aquariids and the
Daytime Arietids, and plays a hand in
the Quadrantids as well. The meteor
flash you witness may be momentary,
but the particle that produced it has a
deep and tangled past.
There are several minor showers
active around the same time as the
Aquariids, including the Alpha Capricornids,
which peak on the same date.
Although they contribute just five meteors
per hour, the Alpha Capricornids are
known for slow-moving fireballs, with
a few streaks brighter than Venus. The
radiant lies about 3° northeast of Alpha
(α) Capricorni and culminates a couple
of hours earlier than the radiant for the
Aquariids. If you're fortunate, you'll get
to sample both meteor streams during
your early morning outing.
Galilean moons, and binoculars usually
show at least two or three. Use the
diagram on the facing page to identify
them by their relative positions on any
given date and time. All the observable
interactions between Jupiter and its satellites
and their shadows are tabulated
on the facing page. Find events timed
for when Jupiter is at its highest.
Features on Jupiter appear closer to
the central meridian than to the limb
for 50 minutes before and after transiting.
Here are the times, in Universal
Time, when the Great Red Spot should
cross Jupiter's central meridian. The
dates, also in UT, are in bold. (Eastern
Daylight Time is UT minus 4 hours.)
June 1: 3:20, 13:15, 23:11; 2: 9:07,
19:03; 3: 4:58, 14:54; 4: 0:50, 10:46,
20:41; 5: 6:37, 16:33; 6: 2:28, 12:24,
22:20; 7: 8:16, 18:11; 8: 4:07, 14:03,
23:58; 9: 9:54, 19:50; 10: 5:46, 15:41;
11: 1:37, 11:33, 21:29; 12: 7:24, 17:20;
13: 3:16, 13:11, 23:07; 14: 9:03, 18:59;
15: 4:54, 14:50; 16: 0:46, 10:41, 20:37;
17: 6:33, 16:28; 18: 2:24, 12:20, 22:16;
19: 8:11, 18:07; 20: 4:03, 13:58, 23:54;
21: 9:50, 19:46; 22: 5:41, 15:37; 23:
1:33, 11:28, 21:24; 24: 7:20, 17:15; 25:
3:11, 13:07, 23:02; 26: 8:58, 18:54; 27:
4:50, 14:45; 28: 0:41, 10:37, 20:32; 29:
6:28, 16:24; 30: 2:19, 12:15, 22:11
July 1: 8:10, 18:05; 2: 4:01, 13:57,
23:52; 3: 9:48, 19:44; 4: 5:40, 15:35; 5:
1:31, 11:27, 21:22; 6: 7:18, 17:14; 7: 3:09,
13:05, 23:01; 8: 8:56, 18:52; 9: 4:48,
14:43; 10: 0:39, 10:35, 20:30; 11: 6:26,
16:22; 12: 2:17, 12:13, 22:09; 13: 8:04,
17:59; 14: 3:56, 13:51, 23:47; 15: 9:43,
19:38; 16: 5:34, 15:30; 17: 1:25, 11:21,
Sky & Telescope - July 2022

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