[extropy-chat] fermi's paradox: m/d approach

[Damien Broderick]

FWIW:

http://www.theage.com.au/articles/2004/01/01/1072908849778.html

A tenth of the stars in the Milky Way may have planets that support advanced
life, Australian scientists have said.

Astronomers have plotted a ring-shaped region of the galaxy where there
might be Earth-like worlds old enough for life to have reached a high level
of evolution.

The sun exists in this "Galactic Habitable Zone", which contains about 10
per cent of all the Milky Way's stars.

Stars within the band have enough heavy elements to form Earth-like planets,
are a safe distance from catastrophic supernova explosions, and have existed
for at least four billion years.

The Australian team, led by Charles Lineweaver from the University of NSW,
used a chemical evolution model of the galaxy to identify the region.

Three-quarters of the stars in the zone were older than the sun, ranging in
age between four and eight billion years.

[etc]