JUNE 2019 OBSERVING
Celestial Calendar
Jupiter Goes Big
JUPITER REACHES OPPOSITION —
opposite the Sun in the sky from our
vantage point on Earth — on June 10th,
when it will be easily spotted with the
naked eye from dusk to dawn. Appear-
ing low in the southeast out of evening
twilight, Jupiter rises with Ophiuchus
to shine at its highest in the south an
hour after local midnight on that date.
Admittedly, high isn’t very high for
northern observers, since Jupiter’s path
is following a southern line at declina-
tion –22°. At opposition, Jupiter climbs
only to a peak altitude of 28° above the
horizon. Finding the steady skies needed
for observing could be a challenge.pCitizen-scientist Kevin M. Gill created this image of Jupiter’s South Equatorial Belt brown barge
(a bar-shaped cloud) from data returned by NASA’s Juno spacecraft. NASA
/^ JPL-CALT
ECH^ /SWRI^/^ MSSS^ /KEVINM.^ G
ILL50 JUNE 2019 • SKY & TELESCOPE
But at least the Planet King is a
showoff, already shining at magni-
tude –2.6 when the month opens and
sporting an apparent diameter of 46′′.
Jupiter’s moons, too, show their best —
or at least their largest — selves when
the parent planet is at opposition.
Any telescope shows the four big
Galilean moons, and binoculars usually
show at least two or three. In binocu-
lars, the moons are all but indistin-
guishable from one another. They orbit
Jupiter at different rates, changing
positions along a straight line from our
point of view on Earth. Use the diagram
on the facing page to identify them bytheir relative positions on any given
time and date.
In a telescope, variations between
Jupiter’s natural satellites in color and
apparent diameters are more obvious.
Io and Europa are the brighter of the
tetrad. Callisto has the darkest surface;
this becomes particularly obvious when-
ever Callisto transits (passes across
the face of) Jupiter. The differences in
the moons’ sizes are subtle but can be
detected under magnifi cation. At oppo-
sition, Io will appear 1.2′′ wide, Europa
1.0′′, Ganymede 1.7′′, and Callisto 1.6′′.
All of the June interactions between
Jupiter and its satellites and their shad-
ows are tabulated on the facing page.
Find events timed for when Jupiter is at
its highest in the early morning hours.
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.)
May 1: 2:37, 12:33, 22:28; 2: 8:24,
18:20; 3: 4:15, 14:11; 4: 0:06, 10:02,
19:58; 5: 5:53, 15:49; 6: 1:44, 11:40,
21:36; 7: 7:31, 17:27; 8: 3:22, 13:18,
23:13; 9: 9:09, 19:05; 10: 5:00, 14:56;
11: 0:51, 10:47, 20:43; 12: 6:38, 16:34;
13: 2:29, 12:25, 22:20; 14: 8:16, 18:12;
15: 4:07, 14:03, 23:58; 16: 9:54, 19:50;
17: 5:45, 15:41; 18: 1:36, 11:32, 21:27;
19: 7:23, 17:19; 20: 3:14, 13:10, 23:05;
21: 9:01, 18:57; 22: 4:52, 14:48; 23:
0:43, 10:39, 20:34; 24: 6:30, 16:26; 25:
2:21, 12:17, 22:12; 26: 8:08, 18:03; 27:
3:59, 13:55, 23:50; 28: 9:46, 19:41; 29:
5:37, 15:33; 30: 1:28, 11:24, 21:19; 31:
7:15, 17:10.
June 1: 3:06, 13:02, 22:57; 2: 8:53,
18:48; 3: 4:44, 14:40; 4: 0:35, 10:31,
20:26; 5: 6:22, 16:17; 6: 2:13, 12:09,
22:04; 7: 8:00, 17:55; 8: 3:51, 13:47,
23:42; 9: 9:38, 19:33; 10: 5:29, 15:24;
11: 1:20, 11:16, 21:11; 12: 7:07, 17:02;
13: 2:58, 12:54, 22:49; 14: 8:45, 18:40;
15: 4:36, 14:32; 16: 0:27, 10:23, 20:18;
17: 6:14, 16:10; 18: 2:05, 12:01, 21:56;
19: 7:52, 17:48; 20: 3:43, 13:39, 23:34;
21: 9:30, 19:26; 22: 5:21, 15:17; 23:
1:12, 11:08, 21:04; 24: 6:59, 16:55; 25:
2:50, 12:46, 22:42; 26: 8:37, 18:33; 27:
4:28, 14:24; 28: 0:20, 10:15, 20:11; 29:
6:07, 16:02; 30: 1:58, 11:53, 21:49.