Sky & Telescope - January 2020 - 50

JANUARY 2020 OBSERVING
Celestial Calendar

Action at Jupiter
JUPITER WAS VISIBLE LOW in evening

Our second featured asteroid,
511 Davida, is a 290-kilometer-wide
ball of carbonaceous goodness and
one of the few that reveals a shape in
ground-based instruments. Its reﬂectance spectrum indicates it's a Type C
asteroid enriched in carbon. Unsurprisingly, its surface is considerably darker
than Astraea's, with an albedo of about
0.06 versus 0.23. Type C asteroids are
related to the CI and CM carbonaceous
chondrite meteorites. They're more
common in the outer part of the main

asteroid belt, exactly where you'll ﬁnd
Davida, which takes its name from the
late-19th, early-20th century American
astronomer David Todd.
Davida begins the month at magnitude 9.9, brightens to 9.5 at opposition,
and fades to 10 by month's end while
embarking on a loop near the bright
star Pollux in Gemini. You couldn't ask
for an easier guide star. And what better
sight on a cold January night than a
carbon-rich asteroid soaking up sun like
a turtle on a log?

Penumbral Lunar Eclipse
SKYWATCHERS IN Europe, Africa, Asia, and western Australia will see a deep
penumbral lunar eclipse on Friday, January 10th. The eclipse begins at 17:08 UT
with maximum at 19:11 UT and conclusion at 21:12 UT. At maximum, 89.5% of
the Moon will dip within Earth's outer, or penumbral, shadow. Observers should
easily notice a "graying" of the Moon's southeastern limb about 20 minutes into
the eclipse. All four of 2020's lunar eclipses are penumbral. Western Hemisphere
observers will witness two of them, a shallow event on the night of July 4-5 and a
deeper one in the early morning hours of November 29-30.

Minima of Algol
Dec.
2
5
8
10
13
16
19
22
25
28
30

UT
6:29
3:18
0:07
20:56
17:45
14:34
11:23
8:12
5:02
1:51
22:40

Jan.
2
5
8
11
14
17
20
22
25
28
31

UT
19:29
16:18
13:08
9:57
6:46
3:36
0:25
21:14
18:03
14:53
11:42

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

JANUARY 2 02 0 * SK Y & TELESCOPE

29
30

18

PERSEUS
38

Algol

21

TRIANGULUM

34

p Perseus stands high 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 in respect to comparison stars of
magnitude 2.1 (Gamma Andromedae) and 3.4
(Alpha Trianguli). Algol remains near minimum
for about 2 hours.

twilight in the ﬁrst week or two of
December 2019 and in conjunction
with the Sun on December 27th. Look
for it to reappear very low in the dawn
sky around January 12th.
When Jupiter is observable, any
telescope shows the four big Galilean
moons, and binoculars usually show at
least two or three. The moons orbit Jupiter at different rates, changing positions
along a nearly straight line from our
point of view on Earth. Use the diagram
at right to identify them by their relative
positions on any given time and date.
All of the January interactions
between Jupiter and its satellites and
their shadows are tabulated on the facing page. Find events timed for Jupiter's
brief period of twilight visibility.
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
Standard Time is UT minus 5 hours.)
December 1: 0:19, 10:14, 20:10;
2: 6:06, 16:02; 3: 1:58, 11:54, 21:49;
4: 7:45, 17:41; 5: 3:37, 13:33, 23:29;
6: 9:25, 19:20; 7: 5:16, 15:12; 8: 1:08,
11:04, 21:00; 9: 6:55, 16:51; 10: 2:47,
12:43, 22:39; 11: 8:35, 18:31; 12: 4:26,
14:22; 13: 0:18, 10:14, 20:10; 14: 6:06,
16:01; 15: 1:57, 11:53, 21:49; 16: 7:45,
17:41; 17: 3:36, 13:32, 23:28; 18: 9:24,
19:20; 19: 5:16, 15:12; 20: 1:07, 11:03,
20:59; 21: 6:55, 16:51; 22: 2:47, 12:42,
22:38; 23: 8:34, 18:30; 24: 4:26, 14:22;
25: 0:17, 10:13, 20:09; 26: 6:05, 16:01;
27: 1:57, 11:52, 21:48; 28: 7:44, 17:40;
29: 3:36, 13:32, 23:27; 30: 9:23, 19:19;
31: 5:15, 15:11
January 1: 1:07, 11:02, 20:58; 2:
6:54, 16:50; 3: 2:46, 12:42, 22:37; 4:
8:33, 18:29; 5: 4:25, 14:21; 6: 0:17,
10:12, 20:08; 7: 6:04, 16:00; 8: 1:56,
11:51, 21:47; 9: 7:43, 17:39; 10: 3:35,
13:31, 23:26; 11: 9:22, 19:18; 12: 5:14,
15:10; 13: 1:05, 11:01, 20:57; 14: 6:53,
16:49; 15: 2:45, 12:40, 22:36; 16: 8:32,
18:28; 17: 4:24, 14:19; 18: 0:15, 10:11,
http://www.skyandtelescope.com/algol
Sky & Telescope - January 2020

Table of Contents for the Digital Edition of Sky & Telescope - January 2020
