Prediction of the 2009 Leonids by J. Vaubaillon (IMCCE),
in collaboration with P. Jenniskens (SETI), J. Watanabe and M. Sato (NAOJ)
Introduction:For a general introduction to meteors see this page
The previous predictions posted earlier on on this page did not mention the presence of 2 Leonid trail in the vicinity of the Earth in Nov. 2009. There are indeed the 1466 trail and the 1533 each causing an outburst at roughly the same time (Nov. 17/11/2009 at 21:50 UT). In addition, the 1567 trail might cause a slight enhancement of activity on 17/11/2009 at 7:27 UT Below are the details for each trail. [url=]The situation in 2008[/url]Given the result of the 2008 Leonids campaign we can re-consider the predictions of the 2009 Leonids caused by the 1466 trail. The revised post-prediction for 2008 were the following:


Year 2008
TraiL 1466
Nrev 16
Time of max: 17/11/2008 at 0:54 (UT)
Sol.Long. 234.9233 deg
dist (au) 0.003683
DeltaA (au) 0.07617
f_M 0.377
ZHR 130 /hr(每小时130颗的天顶流量)

Observations show that the maximum occured ~1hr later than expected, meaning that the trail was not located where we thought it was. The ZHR was close to what was forecasted. Note the high f_M value, coming from the perturbations of the planets, and Jupiter in particular.
The Situation in 2009The general location of the streams is illustrated below


A closer view is provided below. As can be seen there is an encounter with the 1466 and 1533 trails on Nov 17th.


Detailed Results1466 TrailThe situation for 2009 is the following:


The exact same trail (1466) as in 2008 will be encountered in Nov 2009. The forecastings are the following:

Year 2009
TraiL 1466
Nrev 16
Time of max: 17/11/2009 at 21:43 UT (may be 0.5-1hr later)
Sol.Long. 235.54461 deg (idem)
dist (au) -0.000447
DeltaA (au) 0.09939
f_M 0.195
ZHR 115 /hr(将造成每小时115颗的天顶流量)

f_M is less than in 2008 but the trail will be much closer to the Earth, explaining why we expect a quite high ZHR. Initially our expectations were much higher though (Vaubaillon et al 2005b). The recent analysis is based on the revised version of our program, taking into account the observations in 2008. In particular, the time of maximum may be later than expected, as in 2008. The work by E. Lyytinen and M. Nissinen (WGN, 37:4, Aug 2009, 122-124) also predicts a shower at this time and this level of activity. This plus recent changes in our code motivated us to completely re-do the Leonids forecastings, hence the change since last year. However the discrepancy between the expected time of maximum remains, as well as a general higher expected ZHR. Among the possible explanations are: sensitivity to initial conditions (given that the trail is 16 Rev. old) or change of cometary activity (impossible to verify unfortunately).
f_M值比2008年的小,但是回归物将更靠近地球,这也是为什么我们对其作出了很高的流量预测,虽然起初我们的预测更高。新近的分析是基于新修订的程序,考虑了2008年的情况。极大时刻可能会比预期更晚,就像2008年那样。E. Lyytinen和M. Nissinen对此次流星雨的预测也是类似的结果。这些变化促使我们彻底重新对狮子座流星雨进行预报。然而预报间的差异可以用下面几点来解释:原始数据的准确性(这次遭遇的回归物已经绕太阳旋转了16圈)和母彗星活跃性的变化(无法检验)

1533 TrailThis trail will encounter the Earth at almost the same time as the 1466 trail

The circumstances of the encounter are the following:

Year 2009
TraiL 1533
Nrev 14
Time of max: 17/11/2009 at 21:50 UT
Sol.Long. 235.54952 deg
dist (au) 0.000533
DeltaA (au) 0.13093
f_M 0.114
ZHR 80 /hr(将造成每小时80颗的天顶流量)

So the 2 trails will peak together for a total ZHR ~ 200/hr

3D-view of the trail in the Solar System at the time of the shower

Close-up view

2D- and 3D-view of the evolution of the 2 trails in the Solar System between the time of ejection and the time of the shower2D-view of the evolution of the 2 trails between 1466 and 2009

Note the apparition of the 1533 trail after the second return of the comet

3D-view of the evolution of the 2 trails between 1466 and 2009 from the point of view 1

3D-view of the evolution of the 2 trails between 1466 and 2009 from the point of view 2

3D zoom at the Earth from point of view 1

3D zoom at the Earth from point of view 2

1567 TrailThis one will pass further away from the Earth but may produce a noticeable activity

Year 2009
TraiL 1567
Nrev 13
Time of max: 17/11/2009 at 7:27 UT
Sol.Long. 234.94546 deg
dist (au) -0.002026
DeltaA (au) 0.12168
f_M 0.065
ZHR 25 /hr
1102The position of this very old trail is highly uncertain, but if confirmed it may produce a noticeable activity. As a consequence, any event related to this one is highly valuable.
Year 2009
TraiL 1102
Nrev 27
Time of max: 18/11/2009 at 3:29 UT
Sol.Long. 235.78736 deg
dist (au) -0.000318
DeltaA (au) 0.07982973
f_M 0.01986
ZHR 10-50(?) /hr

The year 2009 will not see a Leonid storm, but an outburst for sure. There are still some uncertainties regarding the time of maximum of the 1466 trail [Nov. 17th 2009, 21:43 UT (+1hr?)]. The total level of the shower (ZHR~200/hr) was callibrated using the 2008 observations of the 1466 trail, but nothing is known from the 1533 trail. As a consequence, it will be very interesting to check: The time of maximum of each trail. In particular there might be a difference of up to 1hr between the 1466 and 1533 trail, or they might even be late together, giving us some insight about how well/poorly we know comet 55P's orbit The duration of the shower, for the same reason as above: the 2 trails might be shifted, or not, wrt one another. The apparition of the outburst caused by the 1567 trail, if any: this will tell us about our limits of detection/prediction The orbit of the particles, in order to make the difference between each trail. This is a tricky one, so any data is welcome (contact IMO) The location of the radiant(s), for the same reason.
2009年,我们将不会看到一场狮子座流星暴雨,但肯定是一场爆发。关于1466年回归物造成的极大时刻依然还不很确定。根据2008年对1466年回归物的观测,流星数目的整体水平(每小时天顶流量大约200)也会有摆动。但是我们对1533年回归物还一无所知。所以,对每群回归物造成的极大时间的验证将会很有趣,也能够观察出我们对55P彗星的轨道究竟了解多少。流星雨的持续时间也受到如下因素的影响,两群回归物可能变化了,也可能没有。如果出现1567年回归物引起的爆发,那么将使我们知道探测和预报的局限、流星体的轨道,来区分每群回归物。 所有观测资料都是受欢迎的(联系国际流星组织)。

The predictions for the position of the radiants from the diffferent trails are: For the 1466 trail:

And for 1533:

In theory it should be possible to distinguish between the 2 radiants. In practice it may be tricky. Observations are encouraged in order to differenciate the 2 trails.
Our colleagues from MSFC (D. Moser and B. Cooke) pointed out that the best location to view the outburst caused by the 1466 and 1533 trails will be centered around India and includes: Nepal, Thailand, Western China, Tadjikistan, Afghanistan, Eastern Iran, South Central Russia etc.
理论上,区分这两个辐射点是可能的。实际上,这需要一定技巧。我们鼓励观测者区分这两群回归物。我来自MSFC的同事(D. Moser和B. Cooke)指出,观测1466年和1533年回归物引起的爆发,最好的观测点位于印度、尼泊尔、泰国、中国西部、塔吉克斯坦、阿富汗、伊朗东部、中南部俄罗斯等等。(翻译 空间天文网)


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