8月13日凌晨的英仙座流星雨

C.L.Chan

每年大約在7月25日到8月18日,都是暑期英仙座流星雨出現的時刻,
今年的極大值在8月13日,凌晨4時(HKT),流星數每小時幾十至一百顆.
唯獨受下弦月影響,今大家較難看到暗弱的流星
http://science.nasa.gov/headline ... 2009.htm?list156622
國際流星雨組織的資料摘錄於下
http://www.imo.net/calendar/2009#julsep

Moon near their best this year, there is the possibility they may produce more than one peak again, perhaps also with somewhat increased rates. The usual maximum is due around August 12, 17h30m-20h00m UT (λo = 140°0-140°1), but Esko Lyytinen suggests we may encounter the 1610 Perseid trail earlier on August 12, around 9h00m UT (λo = 139°661). This could produce activity additional to the normal Perseid ZHRs then of a few tens, maybe up to a hundred, probably with a fairly normal magnitude distribution, or perhaps marginally brighter. He further suggests that rates overall could be enhanced above usual by the relative proximity of the annual stream's core, most likely at other times on August 12 ahead of the normal peak. The 19th century trail should pass roughly 0.003 astronomical units inside the Earth's orbit at λo = 139°499, so around 5h UT on August 12, though it may add less than 10 to the ZHR at that point. Naturally, information to verify what takes place will be very valuable despite the Moon, so visual observers are encouraged to try to follow as much of what happens over the possible Perseid maxima as practical.

C.L.Chan

POSSIBLE PERSEID OUTBURST: This year's Perseid meteor shower could be even better than usual. "A filament of comet dust has drifted across Earth's path and when Earth passes through it, sometime between 0800 and 0900 UT (1 - 2 am PDT) on August 12th, the Perseid meteor rate could surge to twice its normal value," says Bill Cooke of NASA's Meteoroid Environment Office. The following profile is based on the debris stream models of veteran forecasters Jeremie Vaubaillon and Mikhail Maslov:

The filament was shed by Perseid parent comet Swift-Tuttle in the year 1610, and this is one of Earth's first encounters with it. "In addition," notes Cooke, "the main Perseid debris stream, which we run into every year, may be denser than normal due to a gravitational enhancement by Saturn. The total combination of these effects could result in as many as 200 meteors per hour (ZHR)."

Bright moonlight will overwhelm the outburst's fainter Perseids, but even a fraction of 200 is a good show. Science@NASA's "The Perseids are Coming" offers observing tips and sky maps.

[ 本帖最後由 C.L.Chan 於 2009-8-5 14:38 編輯 ]

GordonSolo

可惜我當日因為暴雨不能去..