Sky & Telescope - October 2019 - 50

OCTOBER 2019 OBSERVING
Celestial Calendar

Action at Jupiter
JUPITER IS AN EARLY EVENING object

The Southern Taurids
The Taurids are a minor shower associated with 2P/Encke, a comet ﬁrst observed
by French astronomer Pierre Méchain in 1786. Encke has the shortest period (3.3
years) of any known periodic comet. Most of the time, Encke behaves like a cold
asteroid; it becomes active only about 100 days before reaching perihelion (the
closest point in its orbit to the Sun). Encke ejects the majority of its dust between
the 10-day mark of its inbound journey and the 30-day mark of its outbound journey. Between those two points, the comet remains in a dormant state.
The dust trail left behind by Encke is broad, with distinct northern and southern branches that produce multiple meteor showers. This year, the Southern
Taurids (produced by the southern branch of dust, as the name suggests) begin
appearing around September 10th and continue through November 20th. Look
for peak activity, with 5 meteors or so an hour, on the night of October 10th,
three nights before full Moon.
The southern particle stream is known for generating dramatic ﬁreballs, and
shower meteors with absolute magnitudes as bright as -17 have been recorded
in the past. Such brilliant lights mean that some of the meteors could be very
large indeed, with initial bodies perhaps 1 meter wide and masses reaching as
much as 900 kg. The biggest and brightest ﬁreballs have been heard to produce
sonic booms that rumble like thunder as the sound waves descend to Earth.
The radiant of the Southern Taurids falls near the ecliptic, so though observers in the Northern Hemisphere are slightly better placed to watch the shower,
activity will also be visible to those in more southerly locations. To determine if
a meteor is a Southern Taurid, track its trajectory back to the point of origin. If
it appears to emanate from an oval region approximately 20º × 10º centered on
Xi (ξ) Arietis (just outside the bounds of Cetus, next to the Sea Monster's head)
on October 10th, you've seen a shower meteor. The Northern Taurids pick up
around October 20th, and as the Southern radiant moves into Taurus, it may be
difﬁcult to tell which branch of the meteor stream produced the light streak.

Minima of Algol
Sept.
1
4
7
10
12
15
18
21
24
27
30

UT
12:28
9:17
6:05
2:54
23:43
20:31
17:20
14:08
10:57
7:46
4:34

Oct.
3
5
8
11
14
17
20
23
25
28
31

UT
1:23
22:12
19:00
15:49
12:38
9:27
6:15
3:04
23:53
20:42
17:30

These geocentric predictions are from the
recent heliocentric elements Min. = JD
2445641.554 + 2.867324E, where E is any
integer. For a comparison-star chart and
more info, see skyandtelescope.com/algol.

50

OCTOBE R 2 019 * SK Y & TELESCOPE

29
30

18

PERSEUS
38

Algol

21

TRIANGULUM

34

p Perseus stands in the northeastern sky in
the evening. Every 2.7 days, Algol (Beta Persei)
dips from its usual magnitude 2.1 to 3.4 and
back. Use this chart to estimate its brightness
with respect to the convenient comparison
stars of magnitude 2.1 (Gamma Andromedae)
and 3.4 (Alpha Trianguli).

this month, culminating before sunset.
Look for its -2.0-magnitude light in the
southwest as the sky darkens.
Any telescope shows the four big
Galilean moons, and binoculars usually
show at least two or three. In binoculars, the moons are all but indistinguishable 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 by
their relative positions.
All of the October 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 in the evening hours.
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.)
September 1: 9:21, 19:17; 2: 5:12,
15:08; 3: 1:04, 11:00, 20:55; 4: 6:51,
16:47; 5: 2:43, 12:39, 22:34; 6: 8:30,
18:26; 7: 4:22, 14:17; 8: 0:13, 10:09,
20:05; 9: 6:01, 15:56; 10: 1:52, 11:48,
21:44; 11: 7:40, 17:35; 12: 3:31, 13:27,
23:23; 13: 9:19, 19:14; 14: 5:10, 15:06;
15: 1:02, 10:57, 20:53; 16: 6:49, 16:45;
17: 2:41, 12:36, 22:32; 18: 8:28, 18:24;
19: 4:20, 14:16; 20: 0:11, 10:07, 20:03;
21: 5:59, 15:55; 22: 1:50, 11:46, 21:42;
23: 7:38, 17:34; 24: 3:29, 13:25, 23:21;
25: 9:17, 19:13; 26: 5:08, 15:04; 27:
1:00, 10:56, 20:52; 28: 6:48, 16:43; 29:
2:39, 12:35, 22:31; 30: 8:27, 18:22.
October 1: 4:18, 14:14; 2: 0:10,
10:06, 20:02; 3: 5:57, 15:53; 4: 1:49,
11:45, 21:41; 5: 7:37, 17:32; 6: 3:28,
13:24, 23:20; 7: 9:16, 19:11; 8: 5:07,
15:03; 9: 0:59, 10:55, 20:51; 10: 6:46,
16:42; 11: 2:38, 12:34, 22:30; 12: 8:26,
18:21; 13: 4:17, 14:13; 14: 0:09, 10:05,
20:01; 15: 5:56, 15:52; 16: 1:48, 11:44,
21:40; 17: 7:36, 17:32; 18: 3:27, 13:23,
23:19; 19: 9:15, 19:11; 20: 5:07, 15:02;
21: 0:58, 10:54, 20:50; 22: 6:46, 16:42;
http://www.skyandtelescope.com/algol
Sky & Telescope - October 2019

Table of Contents for the Digital Edition of Sky & Telescope - October 2019
