Re: [meteorite-list] Week-Long Meteor Shower to Dazzle (Geminids)
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 [EMAIL PROTECTED] To: Ron Baalke [EMAIL PROTECTED]; Meteorite Mailing List meteorite-list@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 [EMAIL PROTECTED] To: Meteorite Mailing List meteorite-list@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
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 [EMAIL PROTECTED] To: Meteorite Mailing List meteorite-list@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
