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arXiv 1404.2159astro-ph.EP
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双曲线流星：星际流星还是通过重力弹射效应在本地产生的流星？

Hyperbolic meteors: interstellar or generated locally via the gravitational slingshot effect?

Paul A. Wiegert

备注：
40 pages, 8 figures. Submitted to Icarus April 8 2014
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摘要：

来自我们太阳系以外的固体粒子的到来将为我们提供宝贵的科学信息来源。试图在地球大气层中观测到的流星中检测这种星际粒子的尝试几乎完全假设那些以高于太阳系逃逸速度运动的粒子-相对于太阳的双曲线轨道上的粒子-正是正在寻找的太阳系外粒子。在这里，我们表明，双曲粒子可以产生完全在太阳系内的引力散射的行星际尘埃和流星体的行星。这些粒子的寿命必然很短，因为它们很快就逃离了我们的恒星系统;尽管如此，有些粒子到达地球的速度可能与星际流星体的速度相当。其中一些与行星与个别彗星的碎片流相遇有关;然而，这种相遇相对罕见。双曲线散射的零星流星的出现率也相当低。在地球上观测到的光学流星中，每10，000颗中只有一颗是这种局部产生的双曲线流星，其日心速度通常仅比地球轨道上的日心逃逸速度高出100米/秒。水星和金星被预测会产生微弱的“双曲线流星雨”：散射到我们星球的限制性几何形状意味着双曲线流星到达地球的太阳附近的辐射应该随着行星的会合周期而重现。然而，虽然行星散射可以产生速度与星际流星体相当的流星体，并且其通量接近目前这类事件的上限，但双曲线流星体的这种局部产生的组成部分的大多数刚好高于日心逃逸速度，应该很容易与真正的星际流星体区分开来。

英文摘要：

The arrival of solid particles from outside our solar system would present us with an invaluable source of scientific information. Attempts to detect such interstellar particles among the meteors observed in Earth's atmosphere have almost exclusively assumed that those particles moving above the Solar System's escape speed -- particles on orbits hyperbolic with respect to the Sun-- were precisely the extrasolar particles being searched for. Here we show that hyperbolic particles can be generated entirely within the Solar System by gravitational scattering of interplanetary dust and meteoroids by the planets. These particles have necessarily short lifetimes as they quickly escape our star system; nonetheless some may arrive at Earth at speeds comparable to those expected of interstellar meteoroids. Some of these are associated with the encounter of planets with the debris streams of individual comets; however, such encounters are relatively rare. The rates of occurrence of hyperbolically-scattered sporadic meteors are also quite low. Only one of every 10,000 optical meteors observed at Earth is expected to be such a locally generated hyperbolic and its heliocentric velocity is typically only a hundred meters per second above the heliocentric escape velocity at Earth's orbit. Mercury and Venus are predicted to generate weak 'hyperbolic meteor showers': the restrictive geometry of scattering to our planet means that a radiant near the Sun from which hyperbolic meteors arrive at Earth should recur with the planet's synodic period. However, though planetary scattering can produce meteoroids with speeds comparable to interstellar meteors and at fluxes near current upper limits for such events, the majority of this locally-generated component of hyperbolic meteoroids is just above the heliocentric escape velocity and should be easily distinguishable from true interstellar meteoroids.

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