The content you've requested is available without charge only to active Sigma Xi members and
If you are an active member or an individual subscriber, please log in now in order to access this article.
If you are not a member or individual subscriber, you can:
Observations of extrasolar planets, which now number close to 200, help to constrain theories of planet formation. In general, recent findings support the core-accretion model, whereby small solid particles in a protostellar disk agglomerate to form planetesimals, which can grow large enough to attract surrounding gas gravitationally. The result is a gas giant similar to Jupiter or Saturn. But the attributes of some of the extrasolar planets recently discovered, and the stars around which they orbit, suggest that current core-accretion theory is still in need of refinement.
Connect With Us:
An early peek at each new issue, with descriptions of feature articles, columns, and more. Every other issue contains links to everything in the latest issue's table of contents.News of book reviews published in American Scientist and around the web, as well as other noteworthy happenings in the world of science books.
To sign up for automatic emails of the American Scientist Update and Scientists' Nightstand issues, create an online profile, then sign up in the My AmSci area.
JSTOR, the online academic archive, contains complete back issues of American Scientist from 1913 (known then as the Sigma Xi Quarterly) through 2005.
The table of contents for each issue is freely available to all users; those with institutional access can read each complete issue.
View the full collection here.
Receive notification when new content is posted from the entire website, or choose from the customized feeds available.