Satgen 369  Interstellar Meteors  by GM4IHJ              20th April 96

There has long been speculation that Comets and Dust can be ejected
from our Solar System , when the sling shot effect imparted by close
encounters with the major planets raises their speed above solar
system escape velocity. It follows therefore that the same mechanism
may just as easily,send Comets and Dust born in other star systems,
into our solar system.

In 1994/95 UNAMSAT built a satellite, one of whose experiments
employed a radar and associated software which measured the speeds of
dust and minor meteors as they terminated their existence in collision
with the Earths atmosphere. The hope being that this device might
record meteors travelling at speeds above the parabolic limit for
orbits bound to the solar system ( Velocity greater than 73 kms/sec ),
indicating that they might have come from other star systems.

Tragically a launch accident robbed radio amateurs of the opportunity
to carry out this experiment. But now there is news from New Zealand
reporting that a ground based radar there has recorded meteors with
event timings and velocities which firmly suggest a possible extra
solar origin.

The report concentrates on the measurement of about 1500 events,out of
many thousands measured,which produced velocities above 100 kms/sec, (
in order to ensure that the data set contained only particles of extra
solar origin). The data shows strong seasonal variation and suggests
that there are several discrete sources for these interstellar
visitors. The event numbers peak at several times during the year,
which comes as no surprise when account is taken of the fact that the
Earth in its annual orbit round the Sun is constantly changing its
direction of travel with respect to objects of Galactic origin. 

Another feature which appears to bias the data is the fact that as it
orbits around the centre of the Galaxy, our Suns gravity acts like a
vacuum cleaner pulling material in towards it and concentrating that
material down track behind the Suns direction of motion. At this early
stage the New Zealand team suggest that only 2 discrete sources are
evident. One perhaps due to massive A type stars in our part of the
MilkyWay galaxy, the other due to a local stellar cluster associated
with some even more massive B type stars. Both A and B type stars are
much bigger than our G type Sun , and their "Solar " winds are
reported to be much fiercer than our Suns. 

Clearly this is a very encouraging start to the study of interstellar
meteor particles. Hopefully radio amateurs will not have to wait too
long before UNAMSAT 2 is built and launch , so that they can get into
the act.