’tis the season to be jolly
yeah! ’tis the season to be jolly. ’tis the
season to be happie!! happy birthday to me! God’s gift is the
heavens… on the night of my ‘day’, the skies celebrate too. Time to
watch for the night sky on show..
The Geminids Meet Mars…
Written by Tammy Plotner
The evening of December 13th and dawn December 14th of will bring
one of the most hauntingly beautiful and mysterious displays of
celestial fireworks all year - the Geminid meteor shower crowned by
Mars.
The Geminid meteor shower was first noted in 1862 by Robert P. Greg
in England, and B. V. Marsh and Prof. Alex C. Twining of the United
States in independent studies. The annual appearance of the Geminid
stream was weak initially, producing no more than a few per hour, but
it has grown in intensity during the last century and a half. By 1877,
astronomers had realized this was a new annual shower - producing about
14 meteors per hour. At the turn of the last century, the rate had
increased to over 20; and by the 1930s, up to 70 per hour. Only ten
years ago observers recorded an outstanding 110 per hour during a
moonless night… And the Moon on this night will soon set leaving
brilliant Mars to lead the way!
So why are the Geminids such a mystery? Most meteor showers are
historic - documented and recorded for hundreds of years - and we know
them as originating with cometary debris. But when astronomers began
looking for the Geminids’ parent comet, they found none. It wasn’t
until October 11, 1983 that Simon Green and John K. Davies, using data
from NASA’s Infrared Astronomical Satellite, detected an object
(confirmed the next night by Charles Kowal) that matched the orbit of
the Geminid meteoroid stream. But this was no comet, it was an asteroid
- in fact, a 14th magnitude asteroid which is passing Earth tonight
from a distance of less than 18 million kilometers! Now considered a
Potential Hazardous Asteroid (PHA), 3200 Phaeton comes within 3.2
million kilometers of Earth’s orbit about every 17 months. You can
locate Phaeton on the night of the 13/14th about 02:00:00 UT using this
finderchart!
Originally designated as 1983 TB, but later renamed 3200 Phaethon,
this apparently rocky solar system member has a highly elliptical orbit
that places it within 0.15 AU of the Sun during every solar system
tour. But asteroids can’t fragment like a comet - or can they? The
original hypothesis was that since Phaethon’s orbit passes through the
asteroid belt, it may have collided with one or more asteroids,
creating rocky debris. This sounded good, but the more we studied the
more we realized the meteoroid "path" occurred when Phaethon neared the
Sun. So now our asteroid is behaving like a comet, yet it doesn’t
develop a tail.
So what exactly is this "thing?" Well, we do know that 5.1 kilometer
diameter Phaethon orbits like a comet, yet has the spectral signature
of an asteroid. By studying photographs of the meteor showers,
scientists have determined that the meteors are denser than cometary
material, yet not as dense as asteroid fragments. This leads them to
believe Phaethon is probably an extinct comet which has gathered a
thick layer of interplanetary dust during its travels, yet retains the
ice-like nucleus. Until we are able to take physical samples of this
"mystery," we may never fully understand what Phaethon is, but we can
fully appreciate the annual display it produces!
Thanks to the wide path of the stream, folks the world over get an
opportunity to enjoy the show of the Geminids and Mars. The traditional
peak time is tonight as soon as the constellation of Gemini appears,
around mid-evening. The radiant for the shower is near the bright star
Castor - less than a handspan northeast of Mars - but meteors can
originate from many points in the sky. From around 2 AM tonight until
dawn (when our local sky window is aimed directly into the stream) it
is possible to see about one "shooting star" every 30 seconds. The most
successful of observing nights are ones where you are comfortable, so
be sure to use a reclining chair or pad on the ground while looking up…
And dress warmly! Please get away from light sources when possible - it
will triple the amount of meteors you see. Enjoy the incredible and
mysterious Geminids and Mars!
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