From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Thu Aug 07 2003 - 13:43:36 MDT
On Tue, 5 Aug 2003, Kevin Freels wrote:
> It seems to me that the people conducting these searches are limiting
> themselves by putting a "habital" zone around a star.
>
> Anyways, am I way off here? I was just curious and I thought someone
> here might know a bit more about this than I.
Kevin, you are correct that the "traditional" habitable zone has been
somewhat restricted. But this work is probably about 20 or more years
old now.
As more work has become known about carbon cycles, heat radiation
from planets, warming from external sources (like gravity for
Europa) the concept of a strict habitable zone has become less
"fixed". Even the galactic habitable zone as well as the planetary
habitable zone may shift with time (Milan Cirkovic and I are
discussing preparing a paper on this).
The problem currently isn't really the habitable zone but the state
of the technology -- we cannot currently locate planets significantly
less than the mass of Saturn. But there are some improvements in
technology and several space missions that may push us down to
Earth mass planets within the next decade or so.
The stakes are very high within the astronomy and physics communities
as well as at NASA and the European Space Agency. The discovery of
an Earth mass planet, especially in a "traditional" habitable zone,
would be front page news on the New York Times (as well as hundreds
of other papers) -- so you can place money on the fact that there
are hundreds, if not thousands, of people working on making this
happen.
As the list of papers posted by Amara (thank you very much Amara)
points out -- people are working overtime to see just how far
one can extend the "habitable zone" concepts.
Also, people are not limiting searches to the "traditional" habitable
zone. The searches currently detect planets based on mass (or in some cases
size). They do not focus on location within a habitable zone. Because of the
way the searches work they are biased towards detecting planets that
are very large and orbit very close to their stars. So of the 100 or
so exoplanets detected thus far the sample set is somewhat atypical
relative to what is actually "out there".
Robert
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