Also, do we risk being tagged by the Galactic Historical Board, so we are not allowed to make any changes. Getting rid of the smallpox virus? The malaria parasite? Forbidden, if we are a rare historical artifact.
Carl Sagan, check your e-mail. According to Jeff Hecht, in New Scientist,
Our solar system is a Goldilocks among planetary systems. Conditions have to be just right for a disc of dust and gas to coalesce into such a set of neatly ordered planets, a new computer model suggests.Honestly? I think computer models are basically race tracks without the horses.
Similar planetary systems are likely to be a minority in the galaxy, says model developer Edward Thommes of the University of Guelph in Ontario, Canada. Even so, if only 1% of the Milky Way's hundreds of billions of stars have a terrestrial planet with a stable orbit in the habitable zone, the Earth could have plenty of company.
Here's the abstract:
Science 8 August 2008:See also:
Vol. 321. no. 5890, pp. 814 - 817
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Reports Gas Disks to Gas Giants: Simulating the Birth of Planetary Systems
Edward W. Thommes,1,2* Soko Matsumura,2 Frederic A. Rasio2
The ensemble of now more than 250 discovered planetary systems displays a wide range of masses, orbits and, in multiple systems, dynamical interactions. These represent the end point of a complex sequence of events, wherein an entire protostellar disk converts itself into a small number of planetary bodies. Here, we present self-consistent numerical simulations of this process, which produce results in agreement with some of the key trends observed in the properties of the exoplanets. Analogs to our own solar system do not appear to be common, originating from disks near the boundary between barren and (giant) planet-forming.
1 University of Guelph,
Guelph, ON N1G 2W1, Canada.
2 Northwestern University, Evanston, IL
Serious push to find more exoplanets
Exoplanets: Will intelligence be common or rare?