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When Is a Planet Not a Planet?
Articles discusses the debate whether Pluto should be included among the planets. [Atlantic Monthly]
www.theatlantic.com
News release from NASA affirming Pluto's planetary status.
science.nasa.gov
Discusses related discoveries and excerpts.
cfa-www.harvard.edu
Gravity Rules: The Nature of Planethood
Article discussing possible definitions that qualify objects, such as Pluto and Sedna in the Kuiper Belt, as being planets or not.
www.spacedaily.com
National Geographic News: Pluto: Planet or Comet?
Discusses Pluto's similarity to other Kuiper Belt objects, and introduces a 5-way classification scheme for solar system objects to break down the lumping together of dissimilar planets.
news.nationalgeographic.com
SciZone - Ontario Science Centre: Pluto: Planet or Not?
Brief nontechnical introduction to Pluto and similar objects such as Sedna and Quaoar, and a summary of the features that make Pluto different than the other planets. Includes a capsule summary of the arguments for and against calling Pluto a planet.
www.ontariosciencecentre.ca
IAU: Trans-Neptunian Object 2003 UB313
Re-announces formation of a working group to produce a formal definition of a planet, in conjunction with the announcement of this Trans-Neptunian object larger than Pluto, which will not be named pending a formal definition.
www.iau.org
New Horizons: Is Pluto a Planet?
Brief discussion of the controversy, and suggested classification of "Ice Dwarf" for Pluto, Charon, Sedna, and similar objects.
pluto.jhuapl.edu
Argues that Pluto is the most important Kuiper Belt object, not the least important planet, based on its orbit and other properties. From astronomer Dave Jewitt, who studies comets and other primitive solar system bodies.
www.ifa.hawaii.edu
SPACE.com: Pluto's Planet Status Could be Jeopardized by Sedna Discovery
Discusses the ongoing debate over the definition of the term "planet", and suggests that if Pluto should be considered a planet, so should Sedna and similar bodies.
www.space.com
Argues that no commonly-accepted category fits it better. Includes a proposed definition of planet, and a list of known objects meeting it. From Lowell Observatory astronomer Marc W. Buie.
www.lowell.edu
Reviews newly-discovered objects that stretch the definition of the term, including massive superjupiters, free-floating planets, and other exoplanets. Suggests a definition based on the way an object is formed. From astronomer Gibor Basri.
astron.berkeley.edu
CBS News: Pluto: Planet Or Junk Snowball?
Outlines the history of the debate.
www.cbsnews.com
The International Astronomical Union's definition of a planet in the Solar System and ruling on the classification of Pluto.[pdf format]
www.iau.org
Astronomer Upset at New Planet Proposal
Washington Post article describes Michael Brown's disagreement with a proposal to expand the definition of a planet to include, among others, his own discovery.
www.washingtonpost.com