Sky and Telescope - November 2016 - 51

Jupiter's Moons

November Meteors
All October and November, keep a lookout for the sparse but occasionally bright
Taurid meteors. Occasionally the shower
includes spectacular so-called "Halloween
ﬁreballs." These may grab attention anytime
for several weeks, not just on Halloween.
The southern component of the Taurid
shower peaks in mid-October, the northern
component in mid-November. They overlap;
each runs for many weeks. During this time
their large, diﬀuse radiants migrate all the way
from southeastern Pisces across southern
Aries to well east of the Pleiades. The radiant
regions climb the eastern sky during evening,
so no post-midnight vigils are required.
But if it weren't for the possibility of ﬁreballs, this would be considered a modest
shower of minor interest. You might count
only a dozen Taurids per hour even under the

Nov 1

most ideal observing circumstances.
The Taurids are bits of debris from Comet
2P/Encke. They strike the atmosphere at a
relatively slow 31 km per second.
Much briefer is November's Leonid
shower. The spectacular Leonid displays
from 1998 through 2001 are a distant memory; now we settle for a few faint ﬂashes
per hour. Moreover, this year's peak on the
morning of November 17th comes just three
days after a full Moon, so any swift Leonids
you might see will be just a lucky bright few.
The International Meteor Organization
(imo.net) recently added the November Orionids to its calendar of annual showers. For
a week or two centered on November 28th,
careful observers have consistently recorded
a few meteors per hour radiating from a
point above the Hunter's head.

2
3

EAST

WEST

4
5

Europa

6
7
8
9
10
11
12
13
14
15
16

Ganymede

Callisto

your map carefully to determine which of
the tiny specks there is it.
Telescopically, Uranus and Neptune
are deﬁnitely nonstellar: they're 3.7″ and
2.3″ in diameter, respectively. Both have
methane (CH4) in thick, clear upper
atmospheres above a deeper cloud layer.
Methane absorbs red light strongly, giving each a pale-blue tint with possibly a
touch of green. Don't be misled by the
strongly saturated Voyager and Hubble
pictures you've seen - the coloration
is subtle. It's pretty easy to see Uranus
as slightly blue or aquamarine, perhaps
even in binoculars, but perceiving color
in Neptune is more challenging. Sensitivity to color in dim light is one of the
most variable properties of the human
eye from one person to the next. What,
exactly, do you see? What about someone
else looking into the same eyepiece?
On August 6th I took the identical
wide-ﬁeld exposures of Uranus and Neptune at left, running a 6-inch robotic telescope and camera remotely via iTelescope.
These enlargements make the colors look
pretty vivid, while the colors in the back-

ground star ﬁeld show no obvious signs of
being overdone. But don't be surprised if
you see Neptune as just gray. ✦
- J. Kelly Beatty

18
19
20
21

Minima of Algol
Oct.

Nov.

17:45

6:42

14:34

3:31

11:23

0:19

8:11

21:08

5:00

17:57

1:49

14:46

22:38

11:35

19:26

8:24

16:15

5:13

13:04

2:02

9:53

These geocentric predictions are from the
heliocentric elements Min. = JD 2452500.179 +
2.867335E, where E is any integer. Courtesy Gerry
Samolyk (AAVSO). For a comparison-star chart and
more info, see SkyandTelescope.com/algol.

26
27

30
Dec 1

The wavy lines represent Jupiter's four big satellites. The central
vertical band is Jupiter itself. Each gray or black horizontal band is
one day, from 0h (upper edge of band) to 24h UT (GMT). UT dates
are at left. Slide a paper's edge down to your date and time, and
read across to see the satellites' positions east or west of Jupiter.

http://www.imo.net http://www.SkyandTelescope.com/algol

Sky and Telescope - November 2016

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