(meteorobs) a preprint from a meteor survey

[metpaper at Safe-mail.net]

http://arxiv.org/abs/1110.5882

For those not wanting to dig into the depths of the paper itself, the abstract more or less sums up everything about the survey.

Note that not many "negative results" are published in astronomy nowadays, probably because they're confused with "unsuccessful".

But a targetted search for a phenomenon which outlines its reasons in a way where others can assess whether it was a practical way to test for that phenomenon was conducted.  Then if the arguments are valid on the general principles, here that if you search in such and such a way amongst surveyed optical meteors observed in a way liable to detect the population you are interested in, you can perform your test.  The test here was to see if any interstellar meteors of a certain scalesize where seen when a large enough number of optical observations were made liable to detect them, using hyperbolic meteors as the target result / filter.  The conclusion here was that none were so detected, and that's a meaningful piece of information worth noting, I think, rather than an "unsuccessful" search.  It does tell us things.

Anyway, just a bit sideways: sometimes the impression is given, although not stated firmly, that interstellar meteors are always hyperbolic, or kind of similarly always signficantly faster in [geocentric] velocity than around 70 km/s (the latter's an upper limit to do with the nature of the Solar System and "head on" meteor orbits).  They can likely be any speed they wish when they burn up in our atmosphere.  But for any that are significantly greater in speed / in hyperbolic orbits the only mechanism that fits is for them to be extrasolar, ie interstellar, as the Sun is moving through the local interstellar medium faster than its attendant planets are orbiting it (about 20 km/s above the local average as far as I can tell, but I haven't looked too deeply at that, and any particular nearby stars, especially Halo ones, do not necessarily have to be sharing the Sun's direction of motion).  The full paper above likely gives more information on that sort of thing.  I'm a bit rusty on this sort of thing, but I think mm sized meteoroids would've meant sourced from another stellar system, because basic background interstellar grains are micron or much less size (don't take my word for it, look it up), and those have been reported as being detected in the past by radar surveys (though quick scanning the papers online at the moment I can't find either the AMOR or CMOR papers quoting specific sizes for their 'interstellar' meteroid detections).

Cheers

John