by neufer » Sun Dec 13, 2009 6:49 pm
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http://news.nationalgeographic.com/news/2009/12/091213-geminids-geminid-meteor-shower-tonight.html wrote:
Intense Geminid Meteor Shower Peaks Tonight
Andrew Fazekas for National Geographic News
December 13, 2009
<<Late tonight is the peak of the year's most prolific annual cosmic fireworks show—the Geminid meteor shower. The meteor shower has been growing in intensity in recent decades and should be an even better holiday treat than usual this year, since it's falling in a nearly moonless week.
Coming fast on the heels of its more famous cousin the Leonid meteor shower—which peaked less than a month ago—the Geminid show should feature as many as 140 shooting stars per hour between Sunday evening and Monday morning. The Geminids are slow meteors that create beautiful long arcs across the sky—many lasting a second or two.
Favoring observers in the Northern Hemisphere, the Geminids are expected to be most frequent within two hours of 1:10 a.m. ET in the wee hours of Monday.
The shower's radiant—the point in the sky from which the meteors appear to originate—is the constellation Gemini, which rises above the eastern horizon after 9 p.m. local time.
Astronomers recommend observers head outside between 10 p.m. and 5 a.m. local time. As with any meteor shower, the Geminids will be muted in light-polluted cities, but even suburban sky-watchers may catch as many as 60 meteors per hour during peak time.
The Geminids have been historically overlooked, simply because of their timing so close to the busy holiday season and during frigid winter nights, astronomers say. But that's beginning to change, thanks to the Geminids' rising intensity over the past few decades. In fact, for many astronomers, the December meteors have now dethroned the more popular August Perseid meteor shower as the shooting star event of the year.
"It may come as a surprise to many, but the Geminids are currently richer and are brighter on average," said Anthony Cook, astronomy observer at Griffith Observatory in Los Angeles, California.
Why the sudden illumination? Earth is plowing deeper every year into an ancient stream of rocky debris left behind by a mysterious 3.1-mile-wide (5-kilometer-wide) object that orbits the inner solar system, he said. When Earth's atmosphere crosses paths with that debris cloud, the rocks are superheated and burn out—and new Geminids are born.
The Geminid meteors all appear to be chips off a mysterious rocky object called 3200 Phaethon.
Other meteor showers come from material shed by melting comets—which are massive chunks of dirty ice and rock—as they pass close to the sun. But no one knows for sure whether the Geminids' parent object, first identified in 1983, is an asteroid or the core of an ancient comet that simply sputtered out. Recent observations of Phaethon, though, suggest it's a nearly dormant comet, and the Geminids' parent is now officially classified as such by NASA.
The research revealed that Phaethon is the rocky skeleton of a comet that lost its ice after too many close encounters with the sun, according to NASA. The shooting stars' rocky, hard exterior—as well as the fact that they, unprotected by ice, get baked by the sun—may help explain why Geminids are slower and last longer in the sky than other shooting stars, said Peter Brown, a meteor expert at the University of Western Ontario in Canada.
"They have the ability to penetrate deeper into Earth's atmosphere," Brown said, "and burn up at much lower altitudes than meteors associated with the Perseids and Leonids." >>
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http://en.wikipedia.org/wiki/3200_Phaethon wrote:
<<3200 Phaethon (pronounced FAY-ə-thon, sometimes incorrectly spelled Phaeton) is an Apollo asteroid and an extinct comet.
Simon F. Green and John K. Davies, while searching Infrared Astronomical Satellite (IRAS) data for moving objects, discovered 3200 Phaethon (1983 TB) in images from October 11, 1983. It was announced on October 14 in IAUC 3878 along with optical confirmation by Charles T. Kowal, who reported it to be asteroidal in appearance. It was the first asteroid to be discovered by a spacecraft. It measures 5.10 km in diameter.
One of Phaethon's most remarkable distinctions is that it approaches the Sun closer than any other numbered asteroid; its perihelion is only 0.140 AU — less than half Mercury's perihelion distance. It is a Mercury-, Venus-, Earth- and Mars-crosser. The surface temperature at perihelion could reach ~1025 K, or 1400 F. For this reason, it was named after the Greek myth of Phaëton, son of the sun god Helios.
Phaethon's attributes can be argued as being cometary, except that Phaethon has never been observed exhibiting a coma, gas jets, or dust trail. However IAUC 3881 soon after discovery of 3200 Phaethon reported Fred Whipple's observation that "orbital elements of 1983 TB shown on IAUC 3879 are virtually coincident with the mean orbital elements of 19 Geminid meteors photographed with the super-Schmidt meteor cameras". Phaethon thus turned out to be the long-sought parent body of the Geminids meteor shower of mid-December. It is classified as an Apollo asteroid because of its orbital qualities, it has much in common with comets and it is also classified as a B-type asteroid because it is composed of dark material; this too fits well with a cometary origin.
When Phaethon came to perihelion in July 2009, it was brighter than expected. Phaethon approached to 18.1 Gm on December 10, 2007. It will draw nearer in 2017, 2050, 2060, and closer still on December 14, 2093, passing within 0.0198 AU (3.0 Gm).>>
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[quote=" http://news.nationalgeographic.com/news/2009/12/091213-geminids-geminid-meteor-shower-tonight.html"]
Intense Geminid Meteor Shower Peaks Tonight
Andrew Fazekas for National Geographic News
December 13, 2009
<<Late tonight is the peak of the year's most prolific annual cosmic fireworks show—the Geminid meteor shower. The meteor shower has been growing in intensity in recent decades and should be an even better holiday treat than usual this year, since it's falling in a nearly moonless week.
Coming fast on the heels of its more famous cousin the Leonid meteor shower—which peaked less than a month ago—the Geminid show should feature as many as 140 shooting stars per hour between Sunday evening and Monday morning. The Geminids are slow meteors that create beautiful long arcs across the sky—many lasting a second or two. [b][color=#FF0000]Favoring observers in the Northern Hemisphere, the Geminids are expected to be most frequent within two hours of 1:10 a.m. ET in the wee hours of Monday[/color][/b].
The shower's radiant—the point in the sky from which the meteors appear to originate—is the constellation Gemini, which rises above the eastern horizon after 9 p.m. local time. [b][color=#0000FF]Astronomers recommend observers head outside between 10 p.m. and 5 a.m. local time.[/color][/b] As with any meteor shower, the Geminids will be muted in light-polluted cities, but even suburban sky-watchers may catch as many as 60 meteors per hour during peak time.
The Geminids have been historically overlooked, simply because of their timing so close to the busy holiday season and during frigid winter nights, astronomers say. But that's beginning to change, thanks to the Geminids' rising intensity over the past few decades. In fact, for many astronomers, the December meteors have now dethroned the more popular August Perseid meteor shower as the shooting star event of the year.
"It may come as a surprise to many, but the Geminids are currently richer and are brighter on average," said Anthony Cook, astronomy observer at Griffith Observatory in Los Angeles, California.
Why the sudden illumination? Earth is plowing deeper every year into an ancient stream of rocky debris left behind by a mysterious 3.1-mile-wide (5-kilometer-wide) object that orbits the inner solar system, he said. When Earth's atmosphere crosses paths with that debris cloud, the rocks are superheated and burn out—and new Geminids are born.
The Geminid meteors all appear to be chips off a mysterious rocky object called 3200 Phaethon.
Other meteor showers come from material shed by melting comets—which are massive chunks of dirty ice and rock—as they pass close to the sun. But no one knows for sure whether the Geminids' parent object, first identified in 1983, is an asteroid or the core of an ancient comet that simply sputtered out. Recent observations of Phaethon, though, suggest it's a nearly dormant comet, and the Geminids' parent is now officially classified as such by NASA.
The research revealed that Phaethon is the rocky skeleton of a comet that lost its ice after too many close encounters with the sun, according to NASA. The shooting stars' rocky, hard exterior—as well as the fact that they, unprotected by ice, get baked by the sun—may help explain why Geminids are slower and last longer in the sky than other shooting stars, said Peter Brown, a meteor expert at the University of Western Ontario in Canada.
"They have the ability to penetrate deeper into Earth's atmosphere," Brown said, "and burn up at much lower altitudes than meteors associated with the Perseids and Leonids." >>[/quote]------------------------------------
[quote=" http://en.wikipedia.org/wiki/3200_Phaethon"]
<<3200 Phaethon (pronounced FAY-ə-thon, sometimes incorrectly spelled Phaeton) is an Apollo asteroid and an extinct comet.
Simon F. Green and John K. Davies, while searching Infrared Astronomical Satellite (IRAS) data for moving objects, discovered 3200 Phaethon (1983 TB) in images from October 11, 1983. It was announced on October 14 in IAUC 3878 along with optical confirmation by Charles T. Kowal, who reported it to be asteroidal in appearance. It was the first asteroid to be discovered by a spacecraft. It measures 5.10 km in diameter.
One of Phaethon's most remarkable distinctions is that it approaches the Sun closer than any other numbered asteroid; its perihelion is only 0.140 AU — less than half Mercury's perihelion distance. It is a Mercury-, Venus-, Earth- and Mars-crosser. The surface temperature at perihelion could reach ~1025 K, or 1400 F. For this reason, it was named after the Greek myth of Phaëton, son of the sun god Helios.
Phaethon's attributes can be argued as being cometary, except that Phaethon has never been observed exhibiting a coma, gas jets, or dust trail. However IAUC 3881 soon after discovery of 3200 Phaethon reported Fred Whipple's observation that "orbital elements of 1983 TB shown on IAUC 3879 are virtually coincident with the mean orbital elements of 19 Geminid meteors photographed with the super-Schmidt meteor cameras". Phaethon thus turned out to be the long-sought parent body of the Geminids meteor shower of mid-December. It is classified as an Apollo asteroid because of its orbital qualities, it has much in common with comets and it is also classified as a B-type asteroid because it is composed of dark material; this too fits well with a cometary origin.
When Phaethon came to perihelion in July 2009, it was brighter than expected. Phaethon approached to 18.1 Gm on December 10, 2007. It will draw nearer in 2017, 2050, 2060, and closer still on December 14, 2093, passing within 0.0198 AU (3.0 Gm).>>[/quote]------------------------------------