Sky & Telescope - December 2020 - 16

Meteor Watching

What to Expect
Meteors belonging to the Geminid shower are identifiable
because their paths appear to extend back to a small area
near the bright star Castor in Gemini (as shown below).
However, shower members can appear in any part of the sky,
so it doesn't really matter which direction you face. If you
concentrate on the radiant, meteors will appear to diverge in
all directions, but they'll have short paths. Conversely, if you
look in the opposite direction (toward the Great Square of
Pegasus in the evening, or Boötes in the predawn) you'll see
meteors darting along lengthy paths away from you.
One of the best things about the Geminids - unlike most
other meteor showers, including the Perseids - is that you
needn't wait until the wee hours of the morning to enjoy a
good show. In fact, you might spy a Geminid or two at nightfall. Any that appear that early (when the shower's radiant is
hovering near the horizon) will sail majestically across the
sky. These "earthgrazers" are bright meteors that enter our
planet's atmosphere at very shallow angles and skim along
the top layer of air, somewhat like a stone skimming across a

Geminids
80°

Altitude of radiant

utes will pass before the sky again bears fruit. If your watch
happens to occur during a lull in activity, your meteor count
might be a little underwhelming. Viewing for a full hour or
longer ensures that you'll see several peaks and valleys in
shower activity.

December 13-14

80°

40°

60°

60°

40°

40°

Astronomical
twilight
ends

20°

0°
6pm

Astronomical
twilight
begins

20°

0°
8pm

10pm

12am

2am

4am

6am

Local mean time
p PEAK OF THE PEAK As this graph shows, the altitude of the radiant rises and falls throughout the night of the peak. Regardless of your
latitude, the peak occurs around 2 a.m. local time.

lake. You need to be patient, but if you sight just one of these
early evening beauties, you'll already feel well-rewarded.
Gemini will be rising in the east-northeast as the evening
wears on, so the number of meteors that flash into view will
markedly increase as the shower's radiant climbs higher. A
"productive" Geminid watch can start as early as 9 p.m. local
time, when the shower's radiant is already about 30° high, or

q SHIFTING SHOWER The Geminids appear to radiate from a region in northern Gemini, not far from the bright star Castor. As this chart shows,
the position of the radiant shifts over the duration of the display. This year, the Geminids peak on the night of December 13-14, at 1h UT on the 14th.
(Positions are plotted for 0h UT on the dates noted.)

Geminid Meteor Shower
December 13, 9 pm local time
Dec 5

Radiant 10
14
LY N X

Betelgeuse

GEMINI

Castor

ORION

20

Rigel

Pollux

10°

CANIS
MINOR

Procyon

CANIS
MAJOR

Looking East

16

DECEMBER 2 02 0 * SK Y & TELESCOPE

G REGG DINDER M A N / S&T

Sirius



Sky & Telescope - December 2020

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

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Sky & Telescope - December 2020 - Cover2
Sky & Telescope - December 2020 - 1
Sky & Telescope - December 2020 - Contents
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