created the dust lanes?
These were created at the boundary
between the visible (ionized) gas and the
surrounding cloak of invisible (neutral) material.
An instability mechanism operates there. The
most familiar type of instability is the one
that produces those white puffy cumulus clouds
or thunderheads on a summer day. The instability
causing the dust lanes is a different type,
one recognized only about 10 years ago and
named the Vishniac instability (after its
discoverer, the astrophysics theoretician
Ethan Vishniac). In the Vishniac instability
material is moved laterally across a surface,
concentrating into local spots. This is much
like puddles forming on a prairie after a
rain, i.e. small local variations in the surface
cause the material to concentrate in specific
areas. Once concentrated, the neutral material
is dense enough to become visible in silhouette.
These are the dark lanes.
2.Would we really be able
to see IC 4406
without Hubble's power and filtering capabilities?
Yes. We can see the object from
the ground. The object has an IC number (Index
Catalog), indicating that it was first seen
and recorded in the 19th century. What the
HST has allowed us to do is to see the object
in much greater detail and to figure out its
*Questions were done by Rob Britt from Space.com
and answers by C.R. O'dell*