Galactic Dust on the Rise
SPACE AGENCY NEWS RELEASE
Posted: August 10, 2003
early 1992 Ulysses has been monitoring the stream of stardust flowing
through our Solar System. The stardust is embedded in the local galactic
cloud through which the Sun is moving at a speed of 26 kilometres every
second. As a result of this relative motion, a single dust grain takes
twenty years to traverse the Solar System.
by the DUST experiment on board Ulysses have shown that the stream of
stardust is highly affected by the Suns magnetic field.
the 1990s, this field, which is drawn out deep into space by the
out-flowing solar wind, kept most of the stardust out. The most recent
data, collected up to the end of 2002, shows that this magnetic shield has
lost its protective power during the recent solar maximum.
an upcoming publication in the Journal of Geophysical Research ESA
scientist Markus Landgraf and his co-workers from the Max-Planck-Institute
in Heidelberg report that about three times more stardust is now able to
enter the Solar System.
reason for the weakening of the Suns magnetic shield is the increased
solar activity, which leads to a highly disordered field configuration. In
the mid-1990s, during the last solar minimum, the Suns magnetic field
resembled a dipole field with well-defined magnetic poles (North positive,
South negative), very much like the Earth.
Earth, however, the Sun reverses its magnetic polarity every 11 years. The
reversal always occurs during solar maximum. That's when the magnetic
field is highly disordered, allowing more interstellar dust to enter the
is interesting to note that in the reversed configuration after the recent
solar maximum (North negative, South positive), the interstellar dust is
even channeled more efficiently towards the inner Solar System. So we can
expect even more interstellar dust from 2005 onwards, once the changes
become fully effective.
grains of stardust are very small, about one hundredth the diameter of a
human hair, they do not directly influence the planets of the Solar
System. However, the dust particles move very fast, and produce large
numbers of fragments when they impact asteroids or comets. It is therefore
conceivable that an increase in the amount of interstellar dust in the
Solar System will create more cosmic dust by collisions with asteroids and
know from the measurements by high-flying aircraft that 40,000 tonnes dust
from asteroids and comets enters the Earths atmosphere each year. It is
possible that the increase of stardust in the Solar System will influence
the amount of extraterrestrial material that rains down to Earth.