Geminid Meteors Sweeping Toward Earth

An old, reliable meteor shower is heading our way. The annual Geminids
should reach peak activity late on the night of December 13 – 14 (late
Friday night and early Saturday morning).

Along with the better-known Perseids of August, the Geminids are the
strongest of the reliable annual meteor showers that hardly change from
year to year. SKY & TELESCOPE magazine predicts that under good sky
conditions late on the peak night, you might see a “shooting star” every
few minutes on average.

The Geminids won’t be a match for the recent Leonid shower — which
produced half a dozen or more meteors per minute for observers who were
watching under good skies at the right time on the morning of November
19th. But if meteors are what you want to see, the Geminids are almost sure
to serve up a nice helping.

The time to watch will be anytime from about 10 p.m. Friday evening,
December 13th, until the first light of dawn on Saturday morning. Moonlight
will wash the sky and compromise the view until about 2 a.m. (depending on
where you live in your time zone). So the very best time will be the wee
hours between moonset and dawn. (Dawn begins about 90 minutes before your
local sunrise.)

You’ll need no equipment but your eyes. Find a dark spot with an open view
straight up and no bright lights nearby to spoil your night vision. Bring a
reclining lawn chair, bundle up warmly, and bring a sleeping bag; clear
nights get very cold.

“Just lie back and watch the stars,” says SKY & TELESCOPE senior editor
Alan MacRobert. “If the Moon is still up, face a little east of straight
overhead in order to keep the Moon’s glare out of your eyes. Relax and let
your eyes adapt to the dark. Be patient.”

With a little luck you’ll see a Geminid every few minutes on average. After
the Moon sets, they’ll appear as often as once a minute if you have a dark
sky far from the light pollution that hangs above populated areas.

Faint Geminids appear as tiny, quick streaks. Occasional brighter ones may
sail across the heavens for several seconds, leaving brief trains of
glowing smoke.

If you trace each meteor’s direction of flight backward far enough across
the sky, you’ll find that the imaginary line you’re drawing comes from a
spot in the constellation Gemini near the stars Pollux and Castor. This
spot is the shower’s radiant, the perspective point from which all the
Geminids would appear to come if you could see them approaching from the
far distance. The radiant is well up in the east by 10 p.m., nearly
overhead around 2 a.m., and high in the west by the first light of dawn.
But you don’t have to look there. Just watch whatever part of your sky is
darkest.

The Geminid shower is active for several days, not just on its peak night.
You may see a few meteors for two or three nights beforehand and one night
after.

The Geminid meteoroids (particles) are tiny, sand-grain- to pea-sized bits
of rocky debris that have been shed by a small asteroid named Phaethon.
Over the centuries these bits have spread all along the asteroid’s orbit to
form a sparse, moving “river of rubble” hundreds of millions of miles long.
Earth’s own annual orbit around the Sun carries us through this stream of
particles every mid-December.

The particles are traveling 22 miles per second with respect to Earth at
the place where we encounter them. So when one of them strikes the Earth’s
upper atmosphere (about 50 to 80 miles up), air friction vaporizes it in a
quick, white-hot streak.

Amateur meteor watchers who have dark skies and are willing to follow
careful guidelines can carry out scientifically valuable meteor counts, as
described on SKY & TELESCOPE’s Web site at
http://SkyandTelescope.com/observing/objects/meteors/article_98_1.asp.