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10月9日 天龍座流星雨極大預報
（2007年09月15日 14:00）
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□作者:
[1]
Active: October 6 —10
Maximum: October 9; 4h30m UT (λ = 195°4 - but see below)
ZHR = periodic - up to storm levels
Radiant: α = 262°; δ = +54°
Radiant drift: negligible
v∞ = 20 km/s
r = 2.6
TFC: α = 290°; δ = +65° and
α = 288°; δ = +39° (β > 30° N)
The Draconids are primarily a periodic shower which produced spectacular, brief, meteor storms twice last century, in 1933 and 1946, and lower rates in several other years (ZHRs ~ 20 —500+). Most detected showers were in years when the stream's parent comet, 21P/Giacobini-Zinner, returned to perihelion, as it did last in 2005 July.
In 2005 October, a largely unexpected outburst happened near the comet's nodal crossing time, around λ = 195°40 —195°44, probably due to material shed in 1946. Visual ZHRs were ~ 35, though radar detections suggested a much higher estimated rate, closer to ~ 150. The peak was found in radio results too, but it did not record especially strongly that way either. Outlying maximum times from the recent past have spanned from λ = 195°075 (in 1998; EZHRs ~ 700), equivalent to 2007 October 8, 20h30m UT, through the nodal passage time above, to λ 195°63 —195°76 (a minor outburst in 1999, not a perihelion-return year; ZHRs ~ 10 —20), equating to 2007 October 9, 10h —13h UT.
The radiant is circumpolar from many northern hemisphere locations, but is higher in the pre-midnight and near-dawn hours of early October. New Moon on October 11 makes for an almost perfect observing opportunity, whatever the shower may yield — even if that is nothing detectable. Draconid meteors are exceptionally slow-moving, a characteristic which helps separate genuine shower meteors from sporadics accidentally lining up with the radiant.
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責任編輯:skylook
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上一篇︰2007年10月木衛食
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