December Showers: The Geminids
This week marks the peak of the Geminid meteor shower. This several day
event features a constant stream of meteors radiating from a point near the
star Castor in the constellation Gemini. Peaking the morning of December 14
for North American viewers, the Geminid meteor shower should cause as many
as 80 shooting stars per hour. Unfortunately, a nearly full moon will make
it difficult to see all but the brightest of these objects.
The Geminid meteor shower is unique in a number of ways. Unlike most
showers, it is not associated with cometary debris. Instead, the sand-sized
granules that hit the atmosphere during the Geminids were left behind by an
asteroid. This 6.9-km (4.3-mi) chunk of rock, designated Apollo asteroid
3200 Phaethon, has a 1.65-year orbital period, and leaves behind a dense
stream of granular material. As this debris hits Earth’s atmosphere at
about 22 mi/sec (35 km/s), it burns up and creates “shooting stars” that are
consistently rich in number and visually stunning.
Phaethon’s orbit is skewed relative to Earth’s. As a result, Earth’s orbit
will intersect the asteroid’s debris tail for only a few short centuries.
First noticed in the 1860s, this meteor shower will cease around the year
2100. Humanity only has one brief century left to enjoy this consistently
dense yearly meteor shower.
The phase of the Moon during this year’s Geminid meteor shower will make
observing difficult. Under normal circumstances, it is best that observers
find a remote, dark site from which to observe the sky. With a nearly full
moon creating significant light pollution, terrestrial light sources become
less of a concern. Observers wishing to view the Geminids should simply
find a spot with a clear view of the sky and look up.
Visible meteors can appear in all areas of the sky; however, they should
consistently appear to radiate away from the constellation Gemini, from
which they get their name. Between midnight and sunrise on December 14 (the
night of December 13), Gemini will appear in the south and sink toward the
southwest.
Astronomy Magazine’s December issue contains all the information you will
need to observe the Geminids: a finding chart for Gemini, observing times,
and a list of other objects that may interest you. Let the Geminids be your
excuse to spend an evening enjoying the wonders of the winter sky.
Please see: http://www.astronomy.com/content/static/PressRoom/default.asp
For more information, please contact Astronomy Magazine’s astronomer Pamela
Gay at 262-796-8776 or pgay@astronomy.com.
