THE SOUTHWORTH PLANETARIUM
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Altitude: 10 feet below sea level
Founded January 1970
Julian Date: 2458828.16
2019-2020: LXVIII
"What doesn't kill you makes you stronger."
-Nietzsche
THE DAILY ASTRONOMER
Tuesday, December 10, 2019
A Geminid Guide
If you ask us, and we're going to narcissitically assume that you did, it
is in the definitions that astronomy loses its audience. Many other
sciences and other "fields of human endeavor" suffer the same marketing
faux pas: by cheerfully unleashing a deluge of gushing lexicon onto an
unsuspecting audience, the expert attempts to educate through drowning.
Only by closely observing the mackerel-eyed corpses drooping over the
chairs will the jargon-happy lecturer suspect that the edification attempt
has fallen a few "consequently's" short of the mark.
So, as we prepare for the Geminid meteor shower peak, we're going to
closely examine and explain the meteor shower vocabulary which, even by
astronomical standards, can seem a bit off-putting. We'll go bracket-crazy
with annotations as we trudge through a paragraph that would, sans bracket,
be about one tenth as long.
[SANS is an unnecessary synonym of "without" employed unconsciously by
people whose parents used public radio exposure as a punishment.]
On the night of December 13/14th, the Geminid meteor shower peaks.
Astronomers estimate that the ZHR will be about 50
[The ZHR, or Zenithal Hourly Rate is an ideal. It is the hourly meteor
observation rate a seasoned astronomer standing in a dark sky would record
if the RADIANT, the point from which the meteors appear to originate, were
at the ZENITH, the point directly overhead.]
We should not expect to see 50 meteors an hour because the radiant will
not be at our zenith and our sky is not completely dark.
[COMPLETELY DARK is a term that nobody truly understands, even though its
component words are commonplace. Skies have various levels of ambient
light. One will find such light in great abundance in places like downtown
Manhattan or Tokyo. Yet, one can find great amounts of it in smaller
cities. You'll even find ample light pollution if you're sitting on your
apartment balcony avoiding the police spotlight. Out in the suburbs, the
skies are less light polluted, but not dark. A 'completely dark' sky is one
in which ambient light is negligible. Such places are few and far between,
however, unless you're on the ocean, a mountain summit or a remote prairie.]
[Now is a perfect time to sort out three terms: METEOROIDS are the small
particles in outer space that might eventually be captured by Earth's
gravity. When the METEOROIDS descend through the atmosphere, they produce a
light streak called METEORS. If a piece of the METEOROID survives the
descent, it becomes a METEORITE.]
Meteoroid streams are cast off by parent bodies, generally comets. However,
the Geminid meteor shower's parent body is an asteroid named Pantheon. This
parent asteroid is of the B-type, which explains how it could possibly
produce such a torrent of meteoroids.
[Screech to a halt! Asteroids have different types. Some are rock and
metals, but others have different compositions. A B-type is carbonaceous.
One can think of these asteroids as having a charcoal type consistency, at
least along the outer layer.
The surfaces of such asteroids are frissible, much more so than rock-metal
bodies. It is for this reason that our paragraph mentioned that a meteor
shower could possibly be generated by a B-type asteroid.]
We can perhaps expect to see about 30 - 50 meteors an hour, appearing to
emanate from the constellation Gemini. This apparent origin point is an
illusion, for meteoroid travel along path parallel to Earth's surface.
However, from our perspective, the meteors seem to emerge from the region
around Gemini, hence, the term "Geminid" Meteor shower.
[Ok, we're going to move on without annotation.]
We advise observers to look toward the northeast, where these small
asteroid pieces will blaze across the night sky like winter fireworks.
[Blaze: a poetic work always used inappropriately for effect.]
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