El baile de los planetas (II)
David Barrado y Navascués
Seguimos con la discusión sobre qué es y qué no es un planeta…
La reunión de la asamblea general de la Unión Astronómica Internacional continua en Praga. En los diferentes corrillos domina la conversación sobre la propuesta de definición del término «planeta«. Me comentan que el disgusto de un número significativo de astrónomos es grande, el desacuerdo es evidente. La política domina. El sector americano insiste en conservar el status para Plutón, y garantizarlo para 2003 UB(313), ambos descubiertos por americanos, de manera que el Sistema Solar contendría doce planetas en lugar de los nueve tradicionales (o los ocho si se eliminase a Plutón de la lista, opción que yo apoyo). El lobby funciona a diferentes niveles. Un ejemplo, artículo de Gibor Basri y Mike Brown (descubridor de 2003 UB) en astro-ph, el repositorio de artículos astronómicos, esta misma mañana.
Mientas tanto, una propuesta alternativa adquiere más y más fuerza. La votación será este mismo jueves.
Propuesta alternativa, que traduciré a lo largo de la mañana (cortesía de Javier Licandro):
New proposal for Resolution 5: Definition of a Planet
(1) A planet is a celestial body that (a) is by far the largest object in its local population [1], (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) does not produce energy by any nuclear fusion mechanism [3].
(2) According to point (1) the eight classical planets discovered before 1900, which move in nearly circular orbits close to the ecliptic plane are the only planets of our Solar System. All the other objects in orbit around the Sun are smaller than Mercury. We recognize that there are objects that fulfill the criteria (b) and (c) but not criterion (a). Those objects are defined as «dwarf» planets. Ceres as well as Pluto and several other large Trans-Neptunian objects belong to this category. In contrast to the planets, these objects typically have highly inclined orbits and/or large eccentricities.
(3) All the other natural objects orbiting the Sun that do not fulfill any of the previous criteria shall be referred to collectively as “Small Solar System Bodies”.[4]
PD: Traducción de la propuesta alternativa.
Un planeta es un objeto celeste que:
a) es el de mayor objeto de la población local,
b) contiene suficiente masa como para que su fuerza de gravedad sea dominante, de manera que se encuentre en equilibrio hidrostático,
c) no produce energía a partir de reacciones nucleares de fusión.
ENLACES:
Planetas: preguntas y respuestas de la IAU
Más en:
El baile de los planetas
El baile de los planetas (II)
El baile de los planetas (III)
¿Qué es un planeta?…
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