[meteorite-list] Week-Long Meteor Shower to Dazzle (Geminids)

From: K. Ohtsuka <ohtsuka_at_meteoritecentral.com>
Date: Sat, 9 Dec 2006 22:11:55 +0900
Message-ID: <000701c71b93$9a15a240$627e76da_at_LocalHost>

Hello Sterling and all,

Please see also the following papers on Apollo asteroid 2005 UD, mini
Phaethon,
if you are interested in:

Title: Apollo asteroid 2005 UD: split nucleus of (3200) Phaethon?
Authors: Ohtsuka, K.; Sekiguchi, T.; Kinoshita, D.; Watanabe, J.-I.; Ito,
T.; Arakida, H.; Kasuga, Publication: Astronomy and Astrophysics, Volume
450, Issue 3, May II 2006, pp.L25-L28.

The PDF file of my paper is in "paper folder" in the following link:
http://briefcase.yahoo.co.jp/bc/tokyometeor/


Title: Physical Observations of 2005 UD: A Mini-Phaethon
Authors: Jewitt, David; Hsieh, Henry
Publication: The Astronomical Journal, Volume 132, Issue 4, pp. 1624-1629.

The PDF file of Jewitt's paper is in the following link:
http://www.ifa.hawaii.edu/faculty/jewitt/papers/2006/JH06.pdf

Both Phaethon and 2005 UD are F or B-type asteroids, thus linking to
thermally metamorphosed CI/CM.

Katsuhito OHTSUKA
Tokyo, JAPAN

----- Original Message -----
From: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
To: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>; "Meteorite Mailing List"
<meteorite-list at meteoritecentral.com>
Sent: Saturday, December 09, 2006 5:53 AM
Subject: Re: [meteorite-list] Week-Long Meteor Shower to Dazzle (Geminids)


> Hi,
>
> Nice timing, since we've been talking about
> chunks of comet:
>
> > A final point to note are that Geminids stand apart from the other
> > meteor showers in that they seem to have been spawned not by a comet,
> > but by 3200 Phaeton, an Earth-crossing asteroid. Then again, the
> > Geminids may be comet debris after all, for some astronomers
> > consider Phaeton to really be the dead nucleus of a burned-out comet
> > that somehow got trapped into an unusually tight orbit.
>
> Discovered in 1983, Phaethon is 5100 meters
> in diameter and weighs in at 140,000,000 metric
> tons. It has a very dark surface and a density
> (vaguely) calculated at twice that of water.
> Despite being in a cometary orbit and being
> the parent body of a meteor stream in the same
> orbit, it has never shown any coma, dust, or
> gas outbursts. Dead comet? Asteroid? Or can
> we be sure there's really any difference? Yet?
> Phaethon approaches the Sun closer than
> any other numbered asteroid; its perihelion is
> only 0.140 AU, 58% of Mercury's orbital radius.
> The surface temperature at perihelion could
> reach ~1025 K.
> Obviously, it's not a ball of "ice."
> If you plan on hanging around until 2093,
> it will closely approach the Earth, passing
> within 0.0198 AU, on December 14 of that
> year. Only a week and 87 years to go.
> 3200 Phaethon is one of the objects that fit
> unto a pattern of a past breakup of a Comet
> Encke parent body, based on its orbital properties,
> an admittedly controversial idea (but a good one).
> The asteroid 3200 Phaethon was discovered
> as an asteroid, confirmed, plotted, and published,
> before Fred ("Mr. Comet") Whipple pointed out
> that its orbit was identical with that of the
> Geminids.
>
>
> Sterling K. Webb
> --------------------------------------------------------------------------
-
> ----- Original Message -----
> From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
> To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
> Sent: Friday, December 08, 2006 1:46 PM
> Subject: [meteorite-list] Week-Long Meteor Shower to Dazzle (Geminids)
>
>
> >
> > http://www.space.com/spacewatch/061208_night_sky.html
> >
> > Week-Long Meteor Shower to Dazzle
> > By Joe Rao
> > SPACE.com
> > 08 December 2006
> >
> > The annual Geminid meteor shower is expected to produce a reliable
> > shooting star show that will get going Sunday and peak the middle of
> > next week.
> >
> > The Geminid event is known for producing one or two meteors every minute
> > during the peak for viewers with dark skies willing to brave chilly
> > nights.
> >
> > If the Geminid Meteor Shower occurred during a warmer month, it would be
> > as familiar to most people as the famous August Perseids.
> > Indeed, a night all snuggled-up in a sleeping bag under the stars is an
> > attractive proposition in summer. But it's hard to imagine anything more
> > bone chilling than lying on the ground in mid-December for several hours
> > at night.
> >
> > But if you are willing to bundle up, late next Wednesday night into
> > early Thursday morning will be when the Geminids are predicted to be at
> > their peak.
> >
> > Most satisfying shower
> >
> > The Geminids are a very fine winter shower, and usually the most
> > satisfying of all the annual showers, even surpassing the Perseids.
> > Studies of past displays show that this shower has a reputation for
> > being rich both in slow, bright, graceful meteors and fireballs as well
> > as faint meteors, with relatively fewer objects of medium brightness.
> > Many appear yellowish in hue. Some even appear to form jagged or divided
> > paths.
> >
> > Unfortunately, as was the case this year with its summertime
> > counterpart, this year's December Geminids will be hindered somewhat by
> > moonlight, although to a much lesser degree than the brilliant gibbous
> > Moon that wreaked havoc with the Perseids.
> >
> > On Thursday morning, the Moon - a fat waning crescent, two days past
> > last quarter - will come up over the east-southeast horizon by 1:30 a.m.
> > for most locations and will light up the sky in its general vicinity
> > through the rest of the overnight hours. On Friday morning, the Moon
> > will come up about an hour later and will be less of a factor for
> > meteor watching.
> >
> > Where to look
> >
> > These medium speed meteors appear to emanate from near the bright star
> > Castor, in the constellation of Gemini, the Twins, hence the name
> > "Geminid."
> >
> > The track of each one does not necessarily begin near Castor, nor even
> > in the constellation Gemini, but it always turns out that the path of a
> > Geminid extended backward passes through a tiny region of sky about
> > 0.2-degree in diameter (an effect of perspective). In apparent size,
> > that's less than half the width of the Moon. As such, this is a rather
> > sharply defined radiant as most meteor showers go; suggesting the stream
> > is "young" - perhaps only several thousand years old.
> >
> > Generally speaking, depending on your location, Castor begins to come up
> > above the east-northeast horizon right around the time evening twilight
> > is coming to an end [sky map
> >
<http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=061208
_geminds_02.jpg&cap=Sky+Map%3A+Gemini+at+11%3A30+p.m.+on+Dec.+13+from+mid-no
rthern+latitudes.>].
> >
> >
> > As Gemini is beginning to climb the eastern sky just after darkness
> > falls, there is a fair chance of perhaps catching sight of some
> > "Earth-grazing" meteors. Earthgrazers are long, bright shooting stars
> > that streak overhead from a point near to even just below the horizon.
> > Such meteors are so distinctive because they follow long paths nearly
> > parallel to our atmosphere. By around 9 p.m., Gemini will have climbed
> > more than one-third of the way up from the horizon. Meteor sightings
> > should begin to increase noticeably thereafter. By around 2 a.m., Gemini
> > will stand high overhead.
> >
> > Because Geminid meteoroids are several times denser than the cometary
> > dust flakes that supply most meteor showers and because of their
> > relatively slow speed with which they encounter Earth (22 miles/35
> > kilometers per second), Geminid Meteors appear to linger a bit longer in
> > view than most. As compared to an Orionid or Leonid meteor that can
> > whiz across your line of sight in less than a second, a Geminid meteor
> > moves only about half as fast.
> >
> > On a personal note, their movement reminds me of field mice scooting
> > from one part of the sky to another.
> >
> > When to watch
> >
> > The Earth moves quickly through this meteor stream producing a somewhat
> > broad, lopsided activity profile. Hourly rates will start increasing on
> > Sunday night (Dec. 10), appearing roughly above one-quarter peak
strength.
> >
> > Late Wednesday night up until early Thursday morning when the Moon
> > rises, a single observer might average as many as 60 to 120 meteors per
> > hour.
> >
> > After Wednesday night, the rates are expected to drop off more sharply:
> > The rates on Thursday night/Friday morning will have diminished to about
> > 30 to 60 per hour. Yet, there is good reason to keep watching for
> > Geminids even after their peak has passed, for those "late" Geminids,
> > tend to be especially bright. And renegade late stragglers might be seen
> > for a week or more after the night of maximum activity.
> >
> > I brought this up this point earlier, but certainly it should be
> > addressed again: Make sure you're warm and comfortable. Likely your
> > local weather will be more appropriate for taking in a hot bath as
> > opposed to a meteor shower! Warm cocoa or coffee can
> > take the edge off the chill, as well as provide a slight stimulus.
> >
> > A final point to note are that Geminids stand apart from the other
> > meteor showers in that they seem to have been spawned not by a comet,
> > but by 3200 Phaeton, an Earth-crossing asteroid. Then again, the
> > Geminids may be comet debris after all, for some astronomers
> > consider Phaeton to really be the dead nucleus of a burned-out comet
> > that somehow got trapped into an unusually tight orbit.
> >
> > ______________________________________________
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> > Meteorite-list at meteoritecentral.com
> > http://six.pairlist.net/mailman/listinfo/meteorite-list
> >
>
>
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Received on Sat 09 Dec 2006 08:11:55 AM PST