starship-design: For Timothy - The 120 pc Map

["L. Parker" <lparker@cacaphony.net>]

While the interstellar medium as a whole has an average density of about 
0.5 atom per cubic centimeter, the interior of the Local Bubble has a 
density of 0.05 - 0.07 atoms/cc.
Although believed to have been formed by a supernova in the same way that 
the Loop I bubble was formed, the Local Bubble is not spherical. Rather, it 
is elliptical or egg-shaped with its longer axis roughly perpendicular to 
the Galactic plane (see Frisch and York, 1983, ApJ Letters). This may be 
due to the reduction in density of the ISM away from the plane, so that the 
supernova bubble expanded preferentially in this direction, faster into the 
thinner gas. Or could it be that the Local Bubble was originally spherical 
but it is being flattened on the sides by the expansion of neighboring 
bubbles? 


 http://spacsun.rice.edu/~twg/pc120.html

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